Chapter 26: Alterations of Cardiovascular Function

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Ever felt a strange swelling in your legs?

Maybe after a long day.

Or wondered what it really means when your blood pressure readings start, you know, creeping up?

Your cardiovascular system, it's this incredible network,

right?

Highways and byways keeping everything going.

But well, it's also remarkably vulnerable.

Today, we're taking a deep dive into what happens when this amazing system starts to go awry.

We're pulling our insights straight from Understanding Pathophysiology Seventh Edition by Huther, McCants, Brasher's and Rote, a fantastic resource.

And our mission for you, simple, to distill the core concepts, the fascinating mechanisms, and those real world clinical examples.

We want to make even the tricky ideas crystal clear.

Think of this as your shortcut to truly understanding what's happening, you know, down at the cellular and systemic level.

That's exactly right.

We'll navigate this pretty intricate landscape together.

We're exploring everything from, say, vein and artery diseases right through to heart wall disorders, then heart failure, which is critical, and even the complex challenges of shock

and multiple organ dysfunction syndrome.

The goal really is to provide those aha moments, hopefully without overwhelming you with information overload.

Absolutely.

We're going to walk you through how these conditions actually develop and what they mean for the body, just giving you a clearer picture of this vital system.

Okay, let's unpack this.

Starting with issues that can crop up in our venous system.

Diseases of the veins.

All right, let's start with something quite visible, maybe something many of us have seen or even experienced.

Varicose veins, what exactly are they?

And how do they link up to something more serious, like chronic venous insufficiency?

Yeah, it's interesting.

A varicose vein isn't just, you know, a cosmetic thing.

It's a visible sign that blood has actually pooled and stretched out of vein.

Usually one of your legs, like the saphenous veins.

Imagine the blood flow isn't smooth.

It sort of backs up, creating that noticeable, sometimes ropey bulge.

This often happens if the little one -way valves inside the veins get damaged, maybe from an injury or sometimes just from the gradual effects of gravity, like standing for long periods.

That pressure slowly distends the vein wall.

Okay.

So when a valve can't close properly, the pressure builds up below it, the vein swells, and fluid can get pushed out into the surrounding tissue.

That's what causes the edema, the swelling.

Right, the swelling.

Now, if the situation goes on for a long time, it can't progress.

It can lead to what we call chronic venous insufficiency or CVI.

Basically, it means your veins are consistently struggling to get that blood back up to your heart efficiently.

That sustained high pressure leads to sluggish circulation down there, and the tissues aren't getting the oxygen they need.

So you'd start to see persistent swelling in the lower legs, the ankles.

Sometimes the skin even darkens that hyperpigmentation.

Oh, okay.

And because the circulation is so poor, these areas become incredibly vulnerable.

Even minor trauma or an infection can lead to those open sores we call venous stasis ulcers.

Wow.

So treatments start simple then.

Yeah.

Often the first line is simple stuff, elevating your legs, wearing compression stockings to sort of help squeeze that blood uphill.

More advanced options like surgery exist, if needed, of course.

So if blood pooling is a problem, what about actual blood clots?

Deep venous thrombosis, DVT, that sounds quite serious.

It is absolutely.

DVT is a critical concern.

So a thrombus is just a blood clot that's actually stuck to the vessel wall.

And in veins, clots are, well, they're more common than in arteries, mostly because the blood flow is slower and the pressure is lower.

Makes sense.

DVT usually happens in those deep veins of the leg.

And we often talk about something called Virto's triad to understand why they form.

Virto's triad, right?

What's that involve?

It's basically three key factors.

First, venous stasis, that sluggish blood flow, like if you're immobile after surgery, or maybe have heart failure.

Second, damage to the veins inner lining, the endothelium, maybe from trauma, surgery, IV lines.

And third, a hypercoagulable state, meaning your blood is just more prone to clotting.

This can be genetic or related to things like pregnancy, certain cancers, or even taking oral contraceptives.

Okay, so those three things increase the risk.

Exactly.

Now, while DVT itself might not have symptoms, the big danger is if a piece of that clot breaks off, that's a thromboembolist.

If it travels through the bloodstream and lodges in your lungs, it causes a pulmonary embolism.

And that can absolutely be life -threatening.

So diagnosis is key.

Vital.

Often done with a D -dimer blood test and Doppler ultrasound.

Then treatment usually involves anticoagulation therapy, blood thinners, to prevent more clots and let the body break down the existing one.

That's a very clear pathway of risk there.

Okay, what about something that affects the upper body more, like superior vena cava syndrome?

Yeah, good question.

SVCS really makes you ask,

why would a major vein in the chest get blocked?

Superior vena cava syndrome, or SVCS, is when the superior vena cava, that's the large vein bringing blood from your head, neck, and arms back to the heart, gets progressively squeezed or occluded.

And why would that happen?

Well, because it sits inside the thoracic compartment, which is a pretty tight space, the most common cause, unfortunately, is usually a growing tumor, often bronchogenic cancer, lung cancer, pressing on the SVC.

Ah, okay.

And the result, venous distension, you get swelling in the face, neck, arms, maybe a feeling of fullness in the head, even visual disturbances or impaired consciousness if it's severe.

Sounds serious.

It's considered an oncologic emergency.

Diagnosis needs imaging, like a chest x -ray or CT.

And treatment focuses on the underlying cause, often radiation or chemo for cancer, maybe surgery for non -malignant causes.

It really highlights how critical that vessel is to diseases of the arteries.

Okay, so from veins, let's pivot to the arteries.

This is where blood pressure becomes a really huge factor, right?

Hypertension, high blood pressure, it's incredibly common.

How do we define it now?

Right.

Hypertension is defined as a consistent elevation of your systemic arterial blood pressure.

The current guidelines set that threshold at a sustained diastolic pressure of 130 mmHg or a diastolic pressure of 80 mmHg.

130 over 80?

Exactly.

And it really affects a huge chunk of the population, especially folks over 60.

You can see the different stages laid out in table 26 .1 in the text from normal all the way up to hypertensive crisis.

And why does it matter so much?

It's often called the silent killer.

It is, and that's the danger.

Because all stages of hypertension, even the milder ones, increase your risk for damage to organs, what we call target organ damage.

We're talking about myocardial infarction, heart attack, kidney disease, stroke.

The list goes on.

So what's actually behind this quiet but persistent threat?

Is there always a clear cause?

Well, that's the interesting part.

In most cases, maybe 92 to 95%, it's what we call primary hypertension, also known as essential hypertension.

Yeah.

Meaning we can't pinpoint one single specific cause.

It's thought to be a complex interplay, a mix of genetic predisposition and environmental or lifestyle factors.

Like a perfect storm kind of thing.

Kind of, yeah.

Think of it as genetics meeting environment, impacting things like how your kidneys handle sodium,

the activity level of your sympathetic nervous system, your stress response, and the whole renin -angiotensin -aldosterone system, the RAAS.

Figure 26 .3 in the text does a good job illustrating how these factors can shift the leading to increased blood volume and higher pressure.

Okay.

So that's primary.

What about the rest?

The remaining 5 to 8 % is secondary hypertension.

Here, there is an identifiable underlying disorder causing the high blood pressure.

Things like chronic kidney disease, certain endocrine disorders, or even some medications.

And the risk factors for the primary kind.

They're pretty broad and likely familiar to many.

Family history plays a role, advanced age, cigarette smoking's a big one, obesity, a high sodium diet, excessive alcohol consumption, low potassium -calcium -magnesium intake, and glucose intolerance or diabetes.

They all contribute to that complex picture.

It sounds incredibly complex.

How do these factors actually cause the pressure to stay high in primary hypertension?

It really is a complex web.

Let's break it down a bit.

Increased activity in the sympathetic nervous system, your fight or flight system, directly increases heart rate and causes vasoconstriction narrowing of blood vessels.

Both of those boost cardiac output and peripheral resistance, pushing pressure up.

Then you have the RAAS, the renal angiotensin -aldosterone system.

Overactivity here causes your body to retain salt and water, increasing blood volume.

Plus, key hormones like angiotensin II and aldosterone directly cause vasoconstriction and contribute to harmful changes in the blood vessel walls themselves,

endothelial dysfunction, and vascular remodeling.

Remodeling, meaning the vessels actually change.

Exactly.

They can become thicker, stiffer, less able to relax.

This permanently increases peripheral vascular resistance.

So even if the initial trigger goes away, the pressure might stay high because the pipes themselves have changed.

Wow.

And there's more.

Natriuretic hormones, which normally help us excrete sodium at lower pressure, can become dysfunctional.

Inflammation throughout the body plays a significant role.

Obesity is linked to inflammation and RAAS activation.

Insulin resistance, common in diabetes, also contributes.

Figure 26 .4 provides a great visual summary of this tangled web.

It really shows why treatments often need to target multiple pathways.

Maybe a diuretic to reduce volume, an ACE inhibitor to block the RAAS, a beta blocker for the sympathetic system.

It really is a complex dance, isn't it?

So what happens when this high pressure goes unchecked for too long?

You mentioned complicated hypertension.

Right.

If hypertension isn't managed effectively, that sustained high pressure starts to, well, damage the plumbing throughout your body.

We're talking about injury to blood vessels and tissues, leading to that target organ damage we mentioned earlier.

Like what specifically?

Well, the heart muscle can thicken and enlarge.

That's left ventricular hypertrophy.

You can develop angina or chest pain, heart failure.

The kidneys are very vulnerable, leading to chronic kidney disease.

The brain is at risk for stroke or transient ischemic attacks.

Your eyes can suffer retinal damage.

Even the legs can be affected, worsening peripheral artery disease.

Table 26 .2 in the book maps these out clearly.

The mechanism of injury linked to the specific damage in the heart, kidneys, brain, eyes, and lower extremities.

And what about a hypertensive crisis?

That's an acute, severe spike in blood pressure.

We're talking systolic pressure, 180 millimilliHG or higher, or diastolic 120 millimilliHG or higher.

This is a medical emergency.

Why so urgent?

Because that extreme pressure can rapidly damage organs.

It can lead to cerebral edema swelling in the brain and hypertensive encephalopathy with symptoms like headache, confusion, seizures, even coma.

It can cause acute heart failure, kidney injury, or aortic dissection.

It can be fatal if not treated promptly.

And the scary part is that the earlier stages are silent.

Precisely.

That underscores why regular blood pressure checks are so vital.

Treatment involves lifestyle changes, diet, exercise, weight loss, limiting salt and alcohol, and usually medications like diuretics, ACE inhibitors, ARBs, beta blockers, or calcium channel blockers, often in combination.

Okay, shifting gears a bit.

From too much pressure to sometimes too little.

Let's talk about orthostatic hypotension.

What's actually happening when someone feels dizzy or faint just from standing up?

Orthostatic hypotension, sometimes called postural hypotension, is that feeling.

It's defined as a significant drop in blood pressure within three minutes of standing up specifically.

A drop of at least 20 mmH in systolic pressure or 10 mmH in diastolic pressure.

And why does that happen?

Normally when you stand, gravity pulls blood down towards your legs and abdomen.

Your body has this amazing rapid reflex involving baroreceptors, pressure sensors in your arteries.

They detect the shift and trigger your nervous system to constrict blood vessels and increase heart rate almost instantly.

This compensates and keeps blood pressure stable.

But with orthostatic hypotension, these compensatory mechanisms are, well, inadequate.

They don't kick in properly or strongly enough.

So, blood pools in your lower extremities, venous return to the heart decreases, cardiac output drops, and blood pressure falls, reducing blood flow to the brain.

Causing the dizziness.

Exactly.

Dizziness, lightheadedness, blurred vision, feeling weak, sometimes even fainting or It can be acute, may be caused by dehydration, certain medications, or even just prolonged bed rest.

Or it can be chronic, often secondary to underlying diseases like diabetes due to neuropathy affecting the nerves, Parkinson's disease, or other neurological disorders.

How is it managed?

Management focuses on finding and treating the underlying cause if possible.

For many, it involves non -drug approaches, increasing fluid and salt intake to boost blood volume, wearing compression stockings, changing position slowly, and avoiding activities that trigger it.

Sometimes medications are needed to help raise blood pressure.

Right.

Let's move on to aneurysms now.

That sounds like a weak spot in a blood vessel wall.

Where do these typically happen and why?

That's a good way to put it.

An aneurysm is a localized dilation or outpouching of a vessel wall, basically a bulge caused by weakness.

They most commonly occur in the aorta, the body's largest artery, especially the abdominal aorta, simply because it's under constant high pressure and stress.

Like a balloon bulging out.

Exactly.

Figure 26 .5 shows one in the ascending thoracic aorta.

Now we distinguish between true aneurysms, where the bulge involves all three layers of the arterial wall being weakened and stretched, and false aneurysms or pseudoaneurysms.

These are different.

They're actually an extravascular hematoma, a blood clot outside the vessel that communicates with the space inside the vessel,

often caused by trauma or maybe a leak at a surgical suture line.

Figure 26 .6a illustrates this difference.

What causes the weakening in true aneurysms?

The most common culprits are atherosclerosis and hypertension.

Atherosclerosis weakens the wall structure and hypertension constantly pounds on that weakened area, causing it to dilate over time.

Chronic inflammation also plays a role.

Sometimes genetics or infections are involved.

Are they always dangerous?

Symptoms really depend on the location, size, and whether it's compressing nearby structures.

Abdominal aortic aneurysms are often asymptomatic, discovered incidentally, but the big danger is rupture.

A ruptured aortic aneurysm causes sudden, severe pain, often in the back or abdomen, and profound hypotension, a life -threatening emergency.

Cerebral aneurysms, often found in the circle of willis at the base of the brain, are particularly concerning.

Rupture leads to subarachnoid hemorrhage, a type of stroke with high mortality and morbidity.

Symptoms might include a sudden, severe headache, often described as the worst headache of my life.

Treatment involves carefully monitoring smaller, asymptomatic ones, aggressively controlling blood pressure, and risk factors like smoking.

For larger aneurysms, those growing rapidly or ones causing symptoms, surgical repair is usually recommended.

This often involves replacing the weakened section with a synthetic graft, and a related, very serious complication is aortic dissection.

This isn't a bulge, but a tear in the inner layer, the intima.

Blood surges into the vessel wall itself, splitting the layers apart.

Fig.

6 .6b shows this.

It's an emergent situation requiring immediate intervention, usually surgery.

Okay, so weakness is one issue.

What about clots forming inside arteries?

We talked about DVT in veins, but arterial thrombi have different implications, right?

Absolutely.

Arterial thrombi typically form when there's some sort of damage or irritation to the arteries interlining, the intima.

Atherosclerosis is a major cause, creating a roughened surface where platelets can stick and activate the coagulation cascade.

Turbulent or static blood flow, perhaps downstream from an aneurysm or stenosis, can also contribute.

And the consequences?

Well, the thrombus can grow large enough to gradually occlude the artery, causing a skinny or reduced blood flow to the tissue supplied by that artery.

Or, perhaps more dramatically, a piece of the thrombus can break off and travel downstream as a thromboembolus.

An embolus?

That's something blocking a vessel.

Exactly.

Embolism is the obstruction of a vessel by a bolus of matter circulating the bloodstream.

It could be a dislodged thrombus, thromboembolism.

But it could also be air bubbles, aggregated fat, bacteria,

amniotic fluid, or even foreign substances.

Table 26 .3 lists various types.

Where do arterial embolus usually come from?

Most arterial embolus actually originate in the heart.

Think clots forming on damaged heart valves, or in the chambers during atrial fibrillation or after a myocardial infarction.

These then get ejected into the systemic circulation.

And the danger is where they end up.

Precisely.

They travel until they lodge in a vessel small enough to block flow.

This causes sudden ischemia or infarction, tissue death, in the area distal to the obstruction.

If it lodges in a cerebral artery, it causes a stroke.

If it lodges in a coronary artery, it can cause an MI.

If it blocks an artery to a limb, it can cause acute limb ischemia, potentially requiring amputation.

Pain, numbness, pallor, pulselessness, those are critical signs.

Right.

Beyond these acute blockages, what about chronic peripheral vascular diseases affecting the limbs?

Good point.

We should touch on a couple of specific ones.

First, there's thromboangitis obliterans, also known as burger disease.

Burger disease.

Yes.

It's an inflammatory disease, likely autoimmune, affecting peripheral arteries, especially in the hands and feet.

It's strongly, strongly linked to smoking, almost exclusively occurring in heavy smokers.

It causes inflammation and thrombi, containing inflammatory cells to form, leading to permanent occlusion of small and medium -sized arteries.

Clinically, you see pain, tenderness, redness, rubor from dilated capillaries trying to compensate, and sometimes cyanosis from ischemia.

The skin can become thin and shiny, and severe cases can lead to gangrene and amputation.

Treatment?

The absolute most important treatment is smoking cessation.

It's essential to halt the disease progression.

Okay.

And the other one?

Then there's Raynaud Phenomenon.

This is characterized by episodes of vasospasm, sudden constriction of the small arteries, usually in the fingers and toes.

What triggers it?

It's typically triggered by exposure to cold, sometimes emotional stress, or even vibrations.

There's a primary form, Raynaud disease, where the cause is unknown, and a secondary form, Raynaud Phenomenon, which is linked to other underlying systemic diseases like scleroderma, or lupus, or certain occupations.

During an attack, the digits typically turn white, paler, due to lack of blood flow, then blue, cyanosis, as tissues lose oxygen, followed by red rubor, and throbbing pain as blood flow returns.

It can be quite uncomfortable.

Management for Raynaud?

Primarily involves avoiding the triggers, keeping hands and feet warm, managing stress.

Sometimes vasodilating medications are used if attacks are frequent or severe.

All right.

Now, let's really zoom in on perhaps the most significant arterial disease, the foundation for so many problems.

Atherosclerosis.

Yes.

Atherosclerosis is absolutely fundamental.

It's a specific type of arteriosclerosis, which just means hardening of the arteries.

Atherosclerosis is characterized by the buildup of lipid -laden macrophages within the arterial wall, forming distinct lesions called plaques.

And this is the main culprit behind?

It's the leading cause of peripheral artery disease, PAD, coronary artery disease, SAD, and cerebrovascular disease, leading to stroke.

It's a slow, progressive disease that often starts early in life.

How does it actually begin?

What's the process?

The pathophysiology usually starts with injury to the endothelial cells, the inner lining of the artery.

What causes this injury?

Major risk factors like cigarette smoking, hypertension, diabetes, high levels of LDL, cholesterol, low levels of HDL, good

increased C -reactive protein.

So the lining gets damaged?

Then what?

That damaged endothelium becomes inflamed and dysfunctional.

It starts expressing adhesion molecules that attract circulating inflammatory cells, particularly monocytes.

These monocytes migrate into the vessel wall and transform into macrophages.

At the same time, LDL cholesterol also enters the vessel wall and becomes oxidized, which is a key step.

Macrophages abidly engulf this oxidized LDL, becoming loaded with lipids.

These lipid -laden macrophages are what we call foam cells.

Accumulations of these foam cells form the earliest visible lesions, known as fatty streaks.

Figure 26 .8 shows this progression visually.

Over time, these fatty streaks evolve.

Smooth muscle cells migrate from the deeper layers of the artery wall into the lesion, proliferate, and produce extracellular matrix, forming a fibrous cap over the lipid core.

This creates a more advanced lesion, the fibrous plaque.

And these plaques block the artery?

They can, as they grow, they can protrude into the lumen, narrowing the artery and obstructing blood flow.

This is often what causes symptoms like angina or intermittent claudication when the obstruction becomes significant.

But here's where it gets really critical, and figure 26 .7 depicts this progression nicely.

Many plaques, especially those rich in lipids and inflammatory cells with a thin fibrous cap, are considered unstable.

They might not severely obstruct flow on their own, but they are prone to rupture, or erosion.

Plaque rupture.

That sounds bad.

It is.

When an unstable plaque ruptures, it exposes the highly thrombogenic material inside, like the lipid core and tissue factor, to the bloodstream.

This immediately triggers platelet aggregation and activation of the coagulation cascade, leading to rapid formation of a thrombus right on top of the ruptured plaque.

And that thrombus is the real danger?

Often, yes.

This newly formed thrombus can suddenly and completely occlude the artery.

Cutting off blood flow downstream.

This abrupt occlusion is what typically causes acute events like myocardial infarction, heart attack, or ischemic stroke.

We call this a complicated lesion, or a complicated plaque.

So it's not always about how much the plaque narrows the artery, but how stable it is.

Exactly.

Plaque stability is a huge factor.

That's why managing the underlying risk factors, controlling blood pressure, lowering LDL, quitting smoking, managing diabetes, is so crucial.

It's not just about preventing plaque growth, but also about promoting plaque stability and reducing inflammation.

Okay, so if atherosclerosis is the underlying problem, how does it manifest specifically as peripheral artery disease in the limbs, and then critically in the heart as coronary artery disease?

Right.

Peripheral artery disease, or PAD, is simply atherosclerosis affecting the arteries supplying the limbs, most commonly the legs.

As we mentioned, it's very common in smokers and people with diabetes.

The gradually increasing obstruction from plaques often causes intermittent claudication, that characteristic leg pain, cramping, or fatigue during exercise that results with rest.

It's basically the leg muscles not getting enough oxygen during exertion.

And acute problems.

Yes, acute obstruction can happen if a thrombus forms on a plaque or an embolus travels down, causing sudden severe pain, coldness, numbness, and loss of pulse in the limb, the limb -threatening emergency.

Treatment involves risk factor reduction, antiplatelet drugs like aspirin, exercise therapy, and sometimes procedures like angioplasty, stenting, or bypass surgery to improve blood flow.

And the heart, coronary artery disease.

This is when atherosclerosis specifically affects the coronary arteries, the vessels supplying blood to the heart muscle itself.

CAD is the most common type of heart disease and a leading cause of death worldwide.

By narrowing these crucial arteries, CAD diminishes the myocardial blood supply.

When the heart muscle's oxygen demand exceeds the supply, it leads to myocardial ischemia.

The cells are temporarily deprived of oxygen.

Which causes angina.

Yes, often angina pictoris.

If the ischemia is persistent or if a coronary artery becomes completely blocked, typically by a thrombus forming on a ruptured plaque, it results in acute coronary syndromes, ACS.

This spectrum includes unstable angina and most severely myocardial infarction and my heart attack, where heart muscle tissue actually dies.

CAD is such a major killer.

Let's revisit those key risk factors we need to really focus on.

But the ones we can change and the ones we can't.

Absolutely crucial.

The risk factors for CAD largely overlap with those for atherosclerosis itself.

Non -modifiable risks.

The ones you're sort of stuck with include advanced age, male gender, though the risk for women increases significantly after menopause, and having a family history of premature heart disease.

Okay.

Those we can't change.

What about the modifiable ones?

This is where we can make a difference.

The major modifiable risks are first dyslipidemia, that's abnormal levels of lipids, fats in the blood,

specifically high levels of LDL cholesterol, the bad cholesterol, especially if it's oxidized LDL, which is particularly damaging, and also low levels of HDL cholesterol, the good cholesterol that helps remove excess cholesterol from arteries.

Table 26 .4 gives a breakdown of the desirable cholesterol levels.

So cholesterol is key.

What to endothelial injury and also increases the workload on the heart, leading to hypertrophy, cigarette smoking, it's directly toxic to endothelial cells, increases LDL, decreases HDL, promotes inflammation and clotting.

Just bad news all around for arteries.

Diabetes.

Yes.

Diabetes, mellitus, and insulin resistance.

High blood sugar damages the endothelium, promotes inflammation, and it's often associated with other risk factors like dyslipidemia and hypertension.

Obesity, particularly abdominal obesity, and a sedentary lifestyle.

These are strongly linked to inflammation, insulin resistance, hypertension, and dyslipidemia.

And finally, an atherogenic diet, one high in salt, saturated fats, trans fats, and refined sugars, and low in fruits, vegetables, and whole grains.

That covers the big ones.

Are there others?

Yes.

Research continues to identify other contributing factors, sometimes called non -traditional risk factors.

Things like elevated levels of high sensitivity C -reactive protein,

HSCRP, which is a marker of systemic inflammation.

Elevated cardiac diponin, I can indicate ongoing minor myocardial injury.

Adipokines hormones released by fat tissue can have pro or anti -inflammatory effects.

Chronic kidney disease significantly increases risk.

Even things like air pollution, certain medications, and emerging research on the gut microbiome seem to play a role.

It really highlights how interconnected cardiovascular is with overall systemic health and inflammation.

It's a complex picture, definitely.

So how do these risk factors translate into the experience of, say, myocardial ischemia and the symptom of angina?

Right, so myocardial ischemia occurs when the blood flow, and therefore oxygen supply, through those narrowed coronary arteries becomes insufficient to meet the demands of the heart muscle cells.

This imbalance is most often triggered when the heart's workload increases, like during physical exertion, emotional stress, or even after a heavy meal.

The partially occluded atherosclerotic vessel simply can't deliver enough extra blood.

What happens to the heart cells, then?

Within seconds of becoming ischemic, the myocardial cells shift from efficient aerobic metabolism, using oxygen, to much less efficient anaerobic metabolism.

This leads to a buildup of lactic acid, which contributes to the pain of angina and a rapid decline in the cell's ability to contract.

ATP stores deplete quickly.

Figure 26 .1 -Zil illustrates this cascade of ischemic events.

If blood flow isn't restored relatively quickly, typically within about 20 minutes or so, under experimental conditions, that injury becomes irreversible, leading to cell death infarction.

How does this show up clinically?

Most commonly as angina pictoris, that chest pain or discomfort, we distinguish different types.

Stable angina.

This is predictable chest pain, often described as pressure, heaviness, or squeezing, usually brought on by exertion and relieved by rest or nitroglycerin.

The underlying plaque is typically stable.

Prince metal angina.

This is unpredictable chest pain, often occurring at rest, caused by sudden transient vasospasm constriction of a coronary artery, sometimes near a plaque but not always due to obstruction.

Silent ischemia.

This is dangerous because there are no symptoms.

The patient experiences myocardial ischemia, often detectable on ECG monitoring or stress tests, but feels no pain.

It's more common in individuals with diabetes due to nerve damage.

And women might experience it differently.

Yes.

Women sometimes present with atypical symptoms, often termed microvascular angina, possibly related to dysfunction in the smaller coronary vessels rather than large plaques.

Symptoms might be fatigue, shortness of breath, indigestion, or pain in locations other than the chest.

How is ischemia diagnosed?

Diagnosis involves looking at the clinical presentation, risk factors, and key tests.

The electrocardiogram, ECG, is crucial.

Ischemia often causes characteristic changes like ST -segment depression or T -wave inversion, as shown in Figure 26 .1.

Stress testing, exercise or pharmacologic, combined with ECG or imaging, like echocardiography or nuclear scans, helps provoke and detect ischemia.

Coronary angiography can directly visualize the blockages.

And treatment.

Treatment aims to restore the balance between oxygen supply and demand.

Medications like nitrates to dilate coronary arteries, beta blockers to reduce heart rate and contractility, thus demand, and calcium channel blockers, vasodilators and reduce contractility, are mainstays.

Antiplatelet drugs like aspirin are essential.

For significant blockages, revascularization procedures like percutaneous coronary intervention, PCI angioplasty and CABG may be needed to physically improve blood flow.

Okay, so that's ischemia.

Now let's talk about the most severe outcome acute coronary syndromes, including the heart attack itself.

Right.

Acute coronary syndromes, ACS, result from a sudden obstruction of coronary blood flow, leading to more severe and prolonged ischemia, potentially causing irreversible damage.

This sudden obstruction is usually caused by thrombus formation over a ruptured or eroded atherosclerotic plaque.

Figure 26 .1 -2 depicts this common pathway.

ACS includes unstable angina, too.

Yes.

Unstable angina is considered part of the ACS spectrum.

It signifies that a plaque is likely ruptured or fissured, causing transient thrombotic occlusion or vasoconstriction.

The resulting ischemia is prolonged, or occurs at rest, representing a significant warning sign that a major event might be imminent.

However, in unstable angina, the blockage is usually temporary or incomplete, so infarction, cell death, doesn't occur, or is very minimal.

Cardiac biomarkers like troponin remain normal or only slightly elevated.

And myocardial infarction.

Myocardial infarction, MI, or heart attack, is when the prolonged ischemia causes irreversible necrosis, death of myocardial tissue.

This happens when that thrombus formed on a ruptured unstable plaque, often one with a large lipid core and thin fibers cap, like shown in figure 26 .13 persists and completely blocks blood flow for a significant duration.

Figure 26 .14a shows that

and 26 .14b shows the resulting necrosis.

How are MIs classified?

Clinically and on the ECG, we often categorize MIs based on ST segment changes.

Non -ST elevation MI, non -stemming.

The thrombus causes significant occlusion, but maybe not complete or persistent blockage.

There's enough damage to cause necrosis and release cardiac biomarkers like troponin.

But the ECG typically shows ST depression, or T wave inversion, not ST elevation.

The infarct usually involves only the inner layer of the heart wall, subendocardium, ST elevation MI, stemmy.

This usually indicates a complete and persistent blockage by the thrombus.

The ECG shows characteristic ST segment elevation, visualized in figure 26 .15.

This typically results in a larger infarct involving the full thickness of the myocardial wall, transmural infarction.

Stemmy is generally considered more severe and requires immediate reperfusion therapy.

What's happened at the cellular level during an MI?

Within minutes of blood flow cessation, you get oxygen deprivation, the switch to anaerobic metabolism, lactic acid buildup, loss of contractility, and electrolyte disturbances, like potassium leaking out of cells, which can trigger dangerous arrhythmias.

Catecholamines, stress hormones are released, increasing heart rate and oxygen demand, potentially worsening the damage.

Over time, structural changes occur.

There's myocardial stunning temporary loss of surrounding tissue even after blood flow is restored.

Hibernating myocardium refers to tissue that adapts its metabolism to chronic ischemia, remaining viable but non -functional until flow improves.

And importantly, myocardial remodeling occurs.

This is a process over weeks to months where the ventricle changes size, shape, and thickness, mediated by neurohumoral factors like angiotensin II and aldosterone.

While initially adapted, this remodeling often leads to progressive heart failure.

Figure 26 .16 illustrates this detrimental process.

Essentially, over about six weeks, the necrotic tissue is replaced by non -contractile scar tissue.

So what does this actually feel like for the patient and how is it definitively diagnosed and treated?

The classic symptom is sudden severe chest pain, often described as crushing, constricting, or heavy, typically substernal and often radiating to the neck, jaw, left shoulder, or left arm.

It usually lasts longer than angina and isn't relieved by rest or nitroglycerin.

But not always.

Not always.

Associated symptoms like nausea, vomiting, shortness of breath, dyspnea, sweating, diaphoresis, and cool, clammy skin are common.

However, some individuals, especially the elderly, women, or those with diabetes, may experience atypical symptoms like unexplained fatigue, indigestion -like discomfort, or even a silent MI with no pain at all.

Complications can arise quickly, as listed in table 26 .5.

Dysrhythmias are very common, ranging from benign to fatal ventricular fibrillation.

Heart failure, cardiogenic shock, rupture of heart structures, pericarditis, and thromboembolism are all potential serious consequences.

Diagnosis must be rapid.

Absolutely critical.

It relies on a combination of one, clinical history and physical examination.

Two, characteristic ECG changes.

Figure 26 .17 shows typical patterns evolving over time, indicating the location and extent, zones of ischemia, injury, infarction.

STEMI requires immediate recognition.

Three, serial measurements of cardiac biomarkers, especially cardiac troponin CTNI or troponin T -CTNT.

These proteins are released from damaged heart muscle cells, and rising levels are highly specific for MI.

The fourth universal definition of myocardial infarction, detailed in box 26 .2, provides specific criteria based on these elements.

And treatment.

Time is muscle, right?

Time is muscle.

Treatment is urgent, especially for STEMI.

The immediate goals are to relieve pain, restore blood flow, reperfusion, reduce myocardial oxygen demand, and prevent complications.

Initial treatment often includes oxygen, aspirin antiplatelet, nitroglycerin, vasodilator, and morphine for pain and anxiety.

For STEMI, rapid reperfusion is key, either with thrombolytic, clot -busting drugs, or, ideally, emergency PCI angioplasty stenting.

For non -STEMI, management is often more conservative initially, involving anticoagulants and antiplatelet agents, with decisions about angiography and revascularization based on risk assessment.

Long -term medications typically include ACE inhibitors or ARs to prevent remodeling, beta blockers to reduce workload in arrhythmias, and statins, lower cholesterol, stabilized plaques.

Post -EMICARE focuses heavily on managing complications and aggressive secondary prevention through lifestyle changes and medication adherence.

Okay, let's move deeper now, inwards, exploring disorders of the heart wall itself.

Starting with the pericardium, that's the sac around the heart, right?

Exactly.

The pericardium is a double -layered sac that encloses the heart, providing protection and lubrication.

Disorders here are often localized manifestations of other systemic conditions, things like infections, autoimmune diseases, trauma, cancer, or even kidney failure.

What's acute pericarditis?

Acute pericarditis is inflammation of the pericardium.

It's often idiopathic, meaning we don't know the cause, or caused by viruses.

The pericardial membranes become inflamed, roughened, and may produce exudate.

Figure 26 .18 shows inflamed pericardial surfaces.

The classic symptom is sudden onset of severe retro -sternal chest pain.

What's often characteristic is that the pain worsens with breathing deeply or lying down, and might be relieved by sitting up and leaning forward.

It can sometimes radiate to the back.

Can you hear anything?

Yes, often a friction rub.

A scratchy sound heard with a stethoscope as the inflamed layers rub against each other.

The ECG can also show characteristic changes like diffuse ST segment elevation and sometimes PR segment depression.

Treatment is usually focused on the underlying cause and managing inflammation with anti -inflammatory drugs like NSA's eyes or colchicine.

What about fluid buildup in that sac, pericardial effusion?

Right.

Pericardial effusion is the accumulation of excess fluid in the pericardial cavity.

This fluid could be inflammatory exudate, blood as shown in figure 26 .19, pus, or serous fluid.

The danger depends on how much fluid accumulates and how quickly.

If fluid builds up rapidly, even a relatively small amount can increase the pressure inside the pericardial sac significantly.

This can lead to cardiac tamponade.

Camponade, that sounds bad.

It is.

Cardiac tamponade occurs when the interpericardial pressure becomes high enough to compress the heart chambers, particularly the right atrium and ventricle during diastole filling.

This severely restricts the heart's ability to fill with blood.

So the heart can't pump effectively.

Exactly.

It leads to decreased ventricular filling, reduced stroke volume and cardiac output, and a backup of pressure into the venous system,

jugular venous distension.

A classic sign is pulsus paradoxus, an exaggerated drop in systolic blood pressure during inspiration.

Tamponade is a medical emergency requiring urgent drainage of the fluid, usually via pericardiocentesis, needle aspiration.

And constrictive pericarditis.

This is a more chronic condition where the pericardium becomes thickened, fibrotic, and scarred, sometimes calcified.

It essentially encases the heart in a rigid, non -elastic shell, as depicted in Figure 26 .20.

Like tamponade, this rigid shell restricts diastolic filling of all heart chambers, leading to high filling pressures and reduced cardiac output over time.

Symptoms often develop gradually and include exercise intolerance, dyspnea on exertion, fatigue, peripheral edema, and signs of systemic venous congestion.

Treatment often requires surgical removal of the constricting pericardium, pericardial decortication.

Okay, moving from the sac to the muscle itself, the myocardium.

What are cardiomyopathies?

What forms do they take?

Cardiomyopathies are a really diverse group of diseases that primarily affect the heart muscle itself, the myocardium.

They can be primary, meaning confined to the heart, often genetic or idiopathic, or secondary, occurring as part of a larger systemic disease.

They are generally categorized based on their main pathophysiologic effect on the heart muscle, as shown nicely in Figure 26 .21, dilated, hypertrophic, or restrictive.

Let's take those one by one, dilated cardiomyopathy.

Dilated cardiomyopathy, DCM, is the most common type.

It's characterized by impaired systolic function, meaning the heart muscle's ability to contract is weakened.

This leads to enlargement dilation of one or both ventricles, particularly the left ventricle, and thinning of the walls.

Think of a balloon that's been overstretched.

Figure 26 .22 illustrates this ventricular enlargement.

Causes can be idiopathic, genetic, related to infections, myocarditis, toxins like alcohol, ischemia, or valvular disease.

The result is typically heart failure with reduced ejection fraction, HFREF, along with risks of arrhythmias and thromboembolism.

Okay, then hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy, HCM, is often inherited as an autosomal dominant trait.

Here, the issue is abnormal thickening hypertrophy of the myocardial wall, particularly the interventricular septum, the wall between the ventricles, often asymmetrically.

Figure 26 .23 shows this septal thickening.

This thickening can obstruct the outflow of blood from the left ventricle during systole, called hypertrophic obstructive cardiomyopathy, or HOCM.

It also makes the ventricle stiff, impairing diastolic filling.

HCM is a major cause of sudden cardiac death in young athletes due to the risk of ventricular arrhythmias.

And restrictive cardiomyopathy.

Restrictive cardiomyopathy is the least common type.

Here, the primary problem is rigid, noncompliant ventricular walls that resist diastolic filling.

The contractile function might be normal or near normal initially, but the ventricles simply can't relax and fill properly.

Causes include infiltrated diseases like amyloidosis or sarcoidosis or adiopathic fibrosis.

It leads to high diastolic pressures and symptoms of heart failure, often predominantly right -sided failure.

Symptoms seem similar across types.

Often, yes.

Dyspnea, shortness of breath, and fatigue are common across all types due to impaired cardiac output or increased filling pressures.

Chest pain, palpitations, syncope fainting, and manifestations of heart failure can occur depending on the specific type and severity.

Diagnosis relies heavily on echocardiography to visualize the heart's structure and function.

Treatment is tailored to the specific type, managing symptoms, preventing complications like arrhythmias and clots, and addressing the underlying cause if possible.

Severe cases may ultimately require heart transplantation.

And what about the innermost layer, the endocardium?

How do problems there affect the crucial heart valves?

The endocardium lines the heart chambers and, importantly, forms the leaflets of the heart valves.

Damage to the endocardium, often from inflammation or infection, is the primary cause of valvular dysfunction.

This dysfunction typically manifests in one of two ways, as illustrated in Figure 26 .24.

1.

Valvular stenosis.

The valve orifice becomes constricted or narrowed.

This impedes the forward flow of blood through the valve when it's supposed to be open.

The chamber proximal upstream to the synotic valve has to generate higher pressure to push blood through, increasing its workload and often leading to hypertrophy.

2.

Valvular regurgitation, also called insufficiency or incompetence.

The valve leaflets fail to shut completely when the valve is supposed to be closed.

This allows blood to leak backward, regurgitate through the valve.

This backflow increases the volume load on both the chamber receiving the backflow and the chamber pumping against it, leading to dilation and hypertrophy.

Which valves are most commonly affected?

In adults, the valves on the left side of the heart, the mitral valve between the left atrium and left ventricle, and the aortic valve between the left ventricle and the aorta, are most frequently affected, primarily because they handle higher pressures.

Table 26 .6 provides a great detailed comparison of stenosis and regurgitation for each of the four valves, outlining common causes, the resulting cardiovascular changes, and the characteristic heart murmurs they produce.

Can you give an example, say aortic stenosis?

Sure.

Aortic stenosis is the most common valvular abnormality, especially in older adults.

It involves calcification and narrowing of the aortic valve orifice.

This creates resistance to blood flow out of the left ventricle during systole.

To overcome this resistance, the left ventricle has to work much harder, leading to significant hypertrophy.

Eventually, the ventricle may fail.

Classic symptoms include angina, chest pain, syncope, especially on exertion, and dyspnea from heart failure.

Oscultation reveals a characteristic crescendo -decrescendo systolic murmur.

And mitral stenosis.

Mitral stenosis is most often caused by scarring from rheumatic heart disease.

It impairs blood flow from the left atrium into the left ventricle during diastole.

This causes pressure to back up into the left atrium, leading to atrial dilation, pulmonary congestion, and an increased risk of atrial fibrillation and thrombus formation in the atrium.

Clinically, it often presents with dyspnea and produces a low -pitched rumbling diastolic murmur.

So surgical repair or replacement is often needed?

For severe symptomatic valvular disease, yes.

Surgical valve repair or replacement with either a mechanical or biological prosthesis is often necessary to relieve the obstruction or stop the regurgitation, alleviate symptoms, and improve prognosis.

Can you elaborate a bit more on regurgitation?

How does that leaky valve affect the heart?

Sure.

With regurgitation, the key issue is volume overload.

Because blood leaks backward, the chamber pumping the blood has to handle its normal forward stroke volume plus the volume that leaked back.

The chamber receiving the leak also gets overloaded.

Take aortic regurgitation.

The aortic valve fails to close properly during diastole, so blood flows back from the aorta into the left ventricle.

This means the LV has to pump out a much larger volume with each beat, the normal stroke volume plus the regurgitant volume.

This leads to significant LV dilation and hypertrophy over time.

Clinically, it causes a widened pulse pressure, difference between systolic and diastolic BP, and a characteristic high -pitched blowing decrescendo -diastolic murmur.

And mitral regurgitation.

Mitral regurgitation involves backflow from the left ventricle into the left atrium during systole.

This overloads the left atrium with volume, causing it to dilate and increasing the risk of atrial fibrillation.

It also increases the volume the left ventricle has to pump, leading to LV dilation and hypertrophy.

Eventually, this can lead to left heart failure.

It typically causes a pancystolic holocystolic murmur.

What about the right side?

Tricuspid regurgitation.

Tricuspid regurgitation, backflow from the right ventricle to the right atrium, is more common than tricuspid stenosis.

It often occurs secondary to right ventricular enlargement and failure caused by pulmonary hypertension, income from lung disease or left heart failure.

It leads to right atrial enlargement and signs of systemic venous congestion, like peripheral edema and distended neck veins.

And mitral valve prolapse.

That sounds common.

Mitral valve prolapse syndrome, MVPS, is indeed the most common valve disorder in the U .S.

Here, one or both of the mitral valve leaflets below or prolapse upward into the left atrium during ventricular systole, as shown in figure 26 .27.

It may or may not cause significant mitral regurgitation.

While often asymptomatic, some individuals experience symptoms like palpitations, atypical chest pain, dyspnea, fatigue, and anxiety.

On examination, a characteristic mid -systolic click, sometimes followed by late systolic murmur if regurgitation is present, can be heard.

Most cases have an excellent prognosis and don't require specific intervention, but severe regurgitation can develop in a minority.

Okay, let's circle back to rheumatic fever.

You mentioned it can damage valves.

It sounds like a really serious consequence of what starts as a simple infection.

It really is, and it raises that important question.

How can a strep throat lead to potentially permanent heart damage?

Rheumatic fever is a systemic inflammatory disease.

It develops as a delayed exaggerated immune response, typically occurring a few weeks after a group -A hemolytic, streptococcal infection of the pharynx, strep throat, that wasn't properly treated with antibiotics.

So it's an autoimmune reaction.

Essentially, yes.

The immune response mounted against the streptococcal antigens cross -reacts with similar -looking self -antigens found in tissues of the heart, joints, skin, and brain.

Figure 26 .28 illustrates this process of molecular mimicry leading to an autoimmune attack.

And this causes rheumatic heart disease.

If left untreated or after recurrent episodes, this autoimmune inflammation can lead to rheumatic heart disease, RHD.

This primarily involves scarring and deformity of the heart valves, especially the mitral and aortic valves.

The inflammation affects all layers of the heart, pancarditis, causing inflammation of the endocardium leading to valve damage, myocardium, where characteristic lesions called ashoff bodies form, and pericardium.

Acute rheumatic fever presents with symptoms like fever, migratory polyarthritis, joint pain moving from joint to joint, carditis, correa, involuntary movements, and specific skin rashes.

Prompt and complete antibiotic treatment of strep throat is absolutely crucial for primary prevention of rheumatic fever.

RHD may eventually require surgical valve repair or replacement later in life.

And finally, for these heart wall disorders, what about infections of the endocardium itself?

Infective endocarditis.

Infective endocarditis, i .e., is an infection and inflammation of the endocardium, the inner lining of the heart chambers and valves.

It's primarily caused by bacteria, though fungi can also be involved.

How does the infection take hold?

The pathogenesis, nicely illustrated in figure 26 .29, typically requires three elements.

One, endocardial damage.

There needs to be some pre -existing damage or abnormality on the endocardial surface, often on a heart valve.

This could be from congenital heart disease, a prosthetic valve, pre -geseromatic heart disease, or even just turbulent blood flow creating micro injuries.

Two, bacterial adherence.

Microorganisms need to enter the bloodstream, pacteremia.

This can happen during dental procedures, intravenous drug use, surgery, or from indwelling catheters.

These circulating bacteria then adhere to the damaged endocardial site.

Three, formation of vegetations.

Once adhered, the microorganisms proliferate and become embedded within protective thrombi, composed of fibrin and platelets.

These clumps are called vegetations.

Figure 26 .3 shows an example.

They protect the bacteria from host defenses and antibiotics.

What are the signs and symptoms?

Clinical manifestations arise from the infection itself.

Fever, chills, fatigue,

systemic embolization, fragments of the vegetation breaking off and traveling to other organs, potentially causing stroke, kidney infarcts, etc.

And immune complex deposition causing things like arthritis or kidney damage.

Classic signs include fever, new or changed heart murmur, patechial hemorrhages, tiny spots on skin or mucous membranes, Osler nodes, painful nodules on finger stows, and Janeway lesions, painless spots on palm soles.

CS complications are common and serious.

How is it diagnosed and treated?

Diagnosis relies on blood cultures to identify the causative organism and echocardiography, especially transophageal echo, to visualize the vegetations on the valves.

Treatment requires prolonged courses, often four to six weeks, of intravenous antimicrobial therapy targeted at the specific organism.

In some cases, surgeries needed to remove infected vegetations or repair place severely damaged valves.

Now let's try to connect many of these underlying disorders to the big, overarching problem of heart failure.

What is heart failure really at its core?

Right.

Heart failure is a complex clinical syndrome.

At its core, it's the inability of the heart to generate an adequate cardiac output to meet the metabolic demands of the body's tissues, or its ability to do so only at the cost of elevated diastolic filling pressures.

It's a major public health issue, a leading cause of hospitalization, especially in older adults.

The most common underlying causes are ischemic heart disease from CAD and hypertension.

We broadly categorize it into left heart failure, which itself has subtypes, right heart failure, and a less common form called high output failure.

Making these distinctions is really important for understanding the patient's symptoms and guiding treatment.

Let's start with left heart failure then.

You mentioned subtypes.

What's the difference between heart failure with reduced ejection fraction versus preserved ejection fraction?

This is a crucial distinction.

Let's start with heart failure with reduced ejection fraction,

HFREF, often called systolic heart failure.

Here, the key problem is impaired contractility of the left ventricle.

The heart muscle is weakened and simply cannot pump blood out effectively during systole contraction.

The ejection fraction, the percentage of blood pumped out with each beat, is significantly reduced.

Typically defined as less than 40%.

What causes this weakened contraction?

Most commonly, it's due to damage from myocardial infarction.

Other causes include dilated cardiomyopathy or conditions that persistently increase the heart's workload, like uncontrolled hypertension, increased afterload, or certain valve diseases causing volume overload, increased preload.

When contractility decreases, the ventricle doesn't empty properly, leading to increased end systolic and end diastolic volumes.

This triggers compensatory mechanisms, like the Frank Starling mechanism, increased stretch, initially boosts contraction, and neurohumoral activation, RAS, sympathetic nervous system.

But these compensations backfire.

Exactly.

While initially helpful, chronic activation of the RAAS and SNS leads to further vasoconstriction, increasing afterload, salt and water retention, increasing preload, and direct toxic effects on the myocardium, causing further myocyte dysfunction and adverse ventricular remodeling.

Fig.

26 .31 shows this remodeling process.

Increased preload eventually leads to overstretching and worsening failure.

Increased afterload from hypertension, as shown in Fig.

26 .32, puts even more strain on the failing ventricle.

It becomes a vicious cycle depicted well in Fig.

26 .33, where decreasing contractility, increasing preload, and increasing afterload all perpetuate and worsen the condition.

What else is going on physiologically in an HFREF?

It's incredibly complex.

Beyond the RAAS and SNS, inflammatory cytokines are elevated and contribute to myocardial damage.

Natriuretic peptides like B and P are released by the stressed heart in an attempt to counteract the RAAS and promote saltwater excretion.

But they often become overwhelmed.

Insulin resistance and alterations in cellular metabolism also play roles.

And the symptoms?

Clinical manifestations stem mainly from two things.

One, pulmonary vascular congestion due to blood backing up from the failing left ventricle, causing dyspnea, orthopnea, paroxymal nocturnal dyspnea, cough with frothy sputum, pulmonary edema.

And two,

inadequate systemic perfusion due to low cardiac output, causing fatigue, weakness, decreased exercise tolerance, reduced urine output, sometimes confusion.

Management focuses on breaking that vicious cycle with drugs like ACE inhibitors, RBs, beta blockers, diuretics, aldosterone antagonists, and newer agents like ARNIs and SGLT2 inhibitors, alongside managing fluid balance and addressing the underlying costs.

Okay, so that's HFREF, the weak pump.

What about heart failure with preserved ejection fraction, HFPEF?

The pump's strength is okay here.

Yes, that's the paradox.

HFPEF, also known as diastolic heart failure, accounts for nearly half of all heart failure cases, especially in older adults and women, often associated with hypertension and diabetes.

Here, the left ventricle contracts normally or near normally, so the ejection fraction is preserved, typically 50%.

The primary problem lies in impaired diastolic function.

The ventricle is stiff and non -compliant, so it cannot relax and fill properly without abnormally high pressure.

So it can't fill adequately.

Right.

Because the ventricle is stiff, the left ventricular and diastolic pressure, LVEDP, rises significantly even with normal filling volumes.

This high pressure gets transmitted backward into the left atrium and then into the pulmonary circulation, leading to pulmonary venous congestion, pulmonary edema, and pulmonary hypertension.

Even though the pump is strong.

Even though the pump squeeze is okay,

the symptoms are often very similar to HFREF dyspnea on exertion, fatigue, exercise, and tolerance, because the end result is still pulmonary congestion and limitations in cardiac output increase during exertion.

Table 26 .7 provides a good comparison of the features of HFREF and HFPEF.

Causes often relate to conditions that make the ventricle thick and stiff, like hypertension -induced hypertrophy, aging, diabetes, or infiltrative cardiomyopathies.

Treatment for HFPEF is more challenging than for HFREF, focusing mainly on controlling blood pressure, managing volume overload with diuretics, and treating underlying conditions.

Unfortunately, effective therapies that improve mortality in HFPEF are still lacking compared to HFREF.

Okay, so that covers the left side.

What about failure of the right side of the heart?

And what's this high output failure?

Right heart failure is the inability of the right ventricle to provide adequate blood flow into the pulmonary circulation at a normal central venous pressure.

Most commonly, right heart failure results from left heart failure.

When the left ventricle fails, pressure backs up through the lungs, pulmonary hypertension,

increasing the workload on the right ventricle.

Eventually, the right ventricle can't keep up and fails too.

Figure 26 .34 shows this relationship.

So left failure causes right failure?

Often, yes.

When the right ventricle fails, pressure backs up into the systemic venous circulation.

This causes the characteristic signs of right heart failure.

Peripheral edema, swelling in legs and ankles, jugular venous distension, bulging neck veins,

hepatosplenomegaly in large liver and spleen, and sometimes the sites, fluid in the abdomen.

However, right heart failure can also occur independently of left heart failure, usually due to lung diseases that cause pulmonary hypertension, like chronic obstructive pulmonary disease, COPD, or pulmonary fibrosis.

This is often termed core pulmonal.

And high output failure, that sounds counterintuitive.

It does.

High output failure, illustrated in figure 26 .35, is a fascinating condition where the heart's cardiac output is actually normal, or even above normal, yet it's still insufficient to meet the body's unusually high metabolic demands.

The heart is working hard, but it can't keep up.

What kind of situations cause that?

Classic causes include severe anemia, the oxygen carrying capacity of the blood is reduced, so the heart has to pump much more blood volume to deliver adequate oxygen.

Septicemia,

widespread infection triggers systemic vasodilation and increased metabolic rate, demanding very high cardiac output.

Hyperthyroidism, an overactive thyroid gland accelerates cellular metabolism throughout the body, drastically increasing oxygen demands.

Burry berry, thiamine, vitamin B1 deficiency, impairs myocardial energy metabolism and causes peripheral vasodilation.

In these cases, the body's metabolic needs simply outstrip the heart's ability to supply oxygen and nutrients, even though the heart itself might be functioning normally, or even hyperdynamically initially.

Treatment focuses entirely on correcting the underlying condition causing the high demand.

Okay, beyond the heart failing as a pump, there's another major category of problems.

Dysrhythmias or arrhythmias.

What are these disturbances in rhythm?

A dysrhythmia or arrhythmia is simply any disturbance of the normal heart rhythm.

They can range from occasional skipped beats or palpitations that are benign, to sustained rhythms that impair cardiac output, or even life -threatening rhythms like ventricular fibrillation that cause cardiac arrest.

What causes them?

They generally result from either.

One, abnormal impulse generation, problems with the heart's natural pacemaker, the sinoatrial SA node, or impulses arising from other areas of the heart, ectopic foci that shouldn't be firing.

Two, abnormal impulse conduction,

problems with the electrical signals traveling through the heart's specialized conduction pathways, like the AV node or bundle branches, causing delays or blocks.

Table 26 .8 in the text details various disorders of impulse formation, like sinus bradycardia, too slow, sinus tachycardia, too fast, atrial fibrillation, chaotic atrial activity, or premature beats.

It shows their ECG effects, basic pathophysiology, and typical treatments.

Similarly, table 26 .9 focuses on disorders of impulse conduction, like different degrees of atrioventricular, AV block, where the signals delayed or blocked between the atria and ventricles, or bundle branch blocks.

So these tables give a good overview.

Yes, they offer a great snapshot of how these electrical abnormalities manifest on an ECG and how they can affect heart function.

Many dysrhythmias can significantly impair cardiac output by reducing felling time or causing uncoordinated contractions.

They can worsen heart failure, cause symptoms like dizziness or syncope, and some, like ventricular tachycardia or fibrillation, are immediate threats to life.

Understanding the heart's electrical symphony and its potential disruptions is absolutely crucial in cardiology.

V.

Shock.

All right, let's transition now to one of the most critical conditions the body can face.

Shock.

It just sounds devastating.

How is shock actually defined?

Shock is indeed a life -threatening condition.

It's defined as a state of widespread systemic impairment of cellular metabolism that occurs when the cardiovascular system fails to adequately perfuse the body's tissues with oxygenated blood.

It can have many different initiating causes, but the final common pathway in all types of shock is this profound failure of oxygen delivery leading to impaired cellular metabolism, as illustrated in figure 26 .36.

What happens at the cellular level?

Without adequate oxygen, cells are forced to switch from efficient aerobic metabolism to much less efficient anaerobic metabolism.

This has several critical consequences.

One, ATP depletion.

Energy stores, ATP, are rapidly used up and cannot be adequately regenerated.

Two, lactic acidosis.

Anaerobic metabolism produces lactic acid as a byproduct, leading to metabolic acidosis, which disrupts cellular function.

Three, cellular edema.

Failure of energy -dependent ion pumps, like the sodium -potassium pump, causes sodium and water to accumulate inside cells, leading to swelling and further dysfunction.

Four, impaired glucose use.

Cells become resistant to insulin, and glucose uptake and use are impaired, further starving them of energy.

Protein breakdown increases.

This buildup of metabolic waste products and lack of energy eventually leads to cellular damage, leakage of intracellular contents, and ultimately irreversible cell death and organ failure if perfusion isn't restored.

What are the early signs?

Is it always low blood pressure?

That's a key point.

While hypotension, low blood pressure, is a common sign in later stages, the early clinical manifestations often reflect the body's attempts to compensate.

You might see tachycardia, elevated heart rate, increased respiratory rate, tachypnea, cool and clammy skin due to vasoconstriction, and changes in mental status like anxiety, confusion, or lethargy, often before systemic blood pressure drops significantly.

Recognizing these early signs is crucial for timely intervention.

So what are the different types of shock?

How do they differ in what initially goes wrong?

Shock is generally classified based on the underlying cause that leads to that inadequate tissue perfusion.

The main types are, first, cardiogenic shock.

This is essentially pump failure.

The heart itself fails to generate sufficient cardiac output to perfuse tissues despite having adequate intravascular volume.

Usually after a heart attack?

Yes.

The most common cause is severe myocardial infarction, affecting a large portion of the left ventricle.

Other causes include acute valvular dysfunction, like a ruptured papillary muscle,

end -stage cardiomyopathy, or severe arrhythmias.

The body's compensatory responses, like activating the RAAS and SNS, as shown in figure 26 .37,

actually worsen the situation by increasing the already struggling heart's workload and oxygen demand.

Okay, pump failure.

What's next?

Second, hypovolemic shock.

This is caused by insufficient intravascular fluid volume failure.

Like bleeding.

Exactly.

Large losses of whole blood, hemorrhage, plasma, for example, from severe burns, or interstitial fluid, for example, from severe dehydration, vomiting, diarrhea, or third spacing of fluid, lead to decreased preload, stroke volume, and cardiac output.

Compensatory mechanisms, illustrated in figure 26 .38, like increased heart rate and systemic vascular resistance, SVR, kick in initially to maintain pressure, but if volume loss continues, they become overwhelmed, leading to decreased tissue perfusion.

Then there's neurogenic shock.

Third, neurogenic shock, which falls under the broader category of distributive or vasogenic shock.

Here the problem is widespread.

Massive vasodilation.

It results from a loss or imbalance of sympathetic nervous system stimulation to vascular smooth muscle.

This is often caused by severe spinal cord trauma above the T5 level, spinal anesthesia, or certain drugs that block sympathetic outflow.

So the blood volume is okay, but the pipes are too wide.

Precisely.

Blood volume hasn't changed, but the vascular container has suddenly become enormous due to the loss of vasomotor tone.

SVR drops dramatically.

This causes blood to pool in the periphery relative hypovolemia, venous return decreases, and cardiac output falls, leading to hypotension and poor tissue perfusion, as shown in figure 26 .39.

A key feature is often bradycardia, slow heart rate, because sympathetic drive is lost.

What about anaphylactic shock?

Also vasodilation.

Fourth, anaphylactic shock.

This is another type of distributive shock, caused by a widespread hypersensitivity reaction anaphylaxis, triggered by exposure to an allergen, like bee stings, nuts, medications.

It involves a mass release of histamine and other inflammatory mediators from mass cells and vesophils.

These mediators cause widespread vasodilation and a dramatic increase in vascular permeability.

So like neurogenic shock, you get peripheral pooling and relative hypovolemia.

Figure 26 .40 .0 shows this pathway.

But critically, anaphylaxis also involves severe extravascular effects like bronchospasm, laryngospasm, airway swelling, erdicaria hives, and angioedema.

It's a true medical emergency with sudden onset and rapid progression.

And finally, septic shock.

Fifth, septic shock.

This is also the type of distributive shock, but it begins with an infection that progresses to bacteremia, bacteria in the blood.

Then sepsis, a systemic inflammatory response to infection, severe sepsis, sepsis with organ dysfunction, and finally septic shock, sepsis with persistent hypotension despite adequate fluid resuscitation.

The infection triggers a complex and dysregulated host immune response.

There's a massive release of pro -inflammatory and anti -inflammatory cytokines and other mediators, as depicted in Figure 26 .41.

This initially causes widespread vasodilation, often a warm shock phase with high cardiac output, but also damages the endothelium, increases vascular permeability, causes microvascular thrombosis, and eventually leads to decreased myocardial contractility and impaired tissue oxygen extraction.

It's a very complex state involving inflammation, coagulation abnormalities, and altered cellular metabolism.

The surviving sepsis campaign guidelines emphasize rapid diagnosis, fluid resuscitation, early antibiotics, and vasopressors to counteract vasodilation to improve outcomes.

That brings us to our final topic, which sounds like the ultimate endpoint of many critical illnesses, M .O .D .S.

Multiple Organ Dysfunction Syndrome.

Yes, M .O .D .S.

represents the progressive dysfunction or failure of two or more resulting from an uncontrolled inflammatory response to a severe illness or injury.

It's a major cause of mortality in intensive care units.

What triggers it?

Is it always sepsis?

Sepsis is the most common cause, but M .O .D .S.

can also be triggered by other major insults, like severe trauma, major burns, pancreatitis, major surgery, or any type of severe circulatory shock, proteogenic, hypovolemic, etc.

What's the underlying process?

How does one failing organ lead to others failing?

The pathogenesis, illustrated in Figure 26 .42, is complex, but centers on that massive, uncontrolled systemic inflammation.

The initial insult, infection, injury,

activates the neuroendocrine stress response and damages the vascular endothelium throughout the body.

This endothelial damage leads to increased vascular permeability, causing fluid to leak out of vessels into tissues, widespread activation of coagulation, leading to microvascular thrombi potentially progressing to disseminated intravascular coagulation, or DIC, and impaired vasor regulation.

Multiple plasma enzyme cascade complement, coagulation, fibrinolytic, and the keloquinokin system become activated and amplify each other, creating and maintaining a hyperinflammatory and hypercoagulant state.

This systemic chaos leads to a maldistribution of blood flow.

Some areas might be hyperperfused, while others are severely hypoperfused.

There is also hypermetabolism, where the body's energy demands skyrocket.

Critically, there is an imbalance between systemic oxygen delivery and oxygen consumption, leading to a comply -dependent oxygen consumption and widespread tissue hypoxia, even if overall cardiac output seems adequate initially.

This tissue hypoxia and ongoing inflammation ultimately cause individual organs to fail.

MODs typically develop over days to weeks after the initial insult.

Early signs might be subtle.

Low -grade fever, tachycardia, tachypnea, altered mental status.

Often, the lungs are the first organ to show significant dysfunction, manifesting as acute respiratory distress syndrome, ARDS.

This is often followed by signs of liver failure, jaundice, clotting problems, hepatic encephalopathy, renal failure, oliguria or anuria, rising creatinine azotemia, gastrointestinal dysfunction, ileus, hemorrhage, bacterial translocation, cardiovascular instability, worsening hypotension, requiring increasing vasopressor support, myocardial dysfunction,

and central nervous system dysfunction, progressive confusion or coma.

The greater the number of failing organs, the higher the mortality rate.

Is there a specific treatment for MODs?

Unfortunately, there is no specific treatment that directly reverses MODs once it's established.

Management focuses heavily on prevention early and aggressive treatment of the underlying cause, like sepsis or shock.

If MODs develops, treatment becomes primarily supportive.

Controlling infection, maintaining adequate tissue oxygenation and perfusion, fluids, vasopressors, sometimes mechanical ventilation, providing nutritional support, and supporting the function of each individual feeling organ.

Example, dialysis for renal failure, ventilation for respiratory failure.

It's a very challenging condition with high mortality.

Outro.

Wow.

Okay.

That was a truly comprehensive journey, wasn't it?

Right through the cardiovascular system's alterations, we've gone from the seemingly simple swelling of varicose veins all the way to the cellular chaos of shock and that really frightening multi -organ cascade of MODs.

It really was.

And I think we've seen how seemingly small things like subtle changes in a valve or gradual plaque buildup can snowball into major problems.

We saw how hypertension can quietly, insidiously damage organs over years and how atherosclerosis really does lay the groundwork for so many of those acute traumatic events like heart attacks and strokes.

Understanding these intricate mechanisms really underscores both the fragility and sometimes the astonishing resilience of this vital system.

So what does this all mean for you listening, whether you're a student trying to grasp this or just someone interested in being better informed about your health?

I think it means recognizing those subtle signs your body might be giving you sometimes.

Understanding how seemingly separate conditions like diabetes and heart disease are actually deeply interconnected and just appreciating that incredible, incredible complexity involved in keeping your cardiovascular system healthy.

Absolutely.

And it really highlights the profound importance of prevention and early intervention across this whole spectrum of diseases.

From relatively simple lifestyle changes, diet, exercise, not smoking that can dramatically reduce your risk for hypertension and atherosclerosis,

all the way to the need for rapid decisive treatment when acute events like coronary syndromes or shock occur.

Your body's compensatory mechanisms are powerful.

They really are, but they definitely have their limits and can be overwhelmed.

Definitely consider this your launch pad for digging even deeper.

We really hope this deep dive has given you a clearer picture and maybe sparked even more curiosity about the amazing human body.

Maybe think about this.

What part of the cardiovascular system or maybe what condition we discussed surprised you the most today?

Something I'm all over.

Until next time, keep learning.

From the Deep Dive team, thank you so much for joining us.

It's truly been a pleasure guiding you through this complex but endlessly fascinating subject.