Chapter 33: Syncope Evaluation & Differential Diagnosis

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Welcome back to The Deep Dive.

Today we are tackling a topic that it feels like a rite of passage for anyone working in primary care or honestly just anyone who has lived long enough.

Oh absolutely.

You've seen someone hit the floor at a wedding or you know in a crowded subway car, it happens.

It does and it's always so dramatic.

It's pure drama.

So today we are diving into chapter three of Advanced Health Assessment and Clinical Diagnosis in Primary Care and our topic is syncope.

That's right syncope which is you know really just the fancy medical term for fainting and it's one of those clinical presentations that can be incredibly

stark in the moment.

Someone just collapses, it looks terrifying, people around them start to panic but the causes and this is the whole point of our deep dive today.

The causes range from the completely benign.

I like the I forgot to eat lunch and stood up too fast kind of thing.

Exactly.

That's probably the most common but it goes all the way to the catastrophic like my heart just beating properly and telling the difference is everything.

Exactly and the text we have in front of us today it really lays this whole thing out as a kind of detective story.

That's a great way to put it.

It's all about navigating the diagnostic reasoning process but the catch is that your patient is usually sitting right in front of you looking totally fine.

The event is over.

Right.

You're essentially investigating a crime scene after the yellow tape has been taken down and all the evidence has been swept up.

That is the absolute central challenge.

You almost never see this thing could be happen in the exam room.

Never.

You're investigating a history.

You're relying on someone's memory or even better a witness's memory of a very stressful event and the stakes are just remarkably high.

Because you have to distinguish between the person who just needs to what drink more water and eat a sandwich and the person who is for lack of term a walking time bomb.

A walking time bomb.

That's exactly it and your job with just your history and physical exam skills is to figure out which one is sitting in your office.

Okay so let's start with the basics then.

The text defines syncope in a very very specific way.

It does and we should probably break it down.

It's the transient loss of consciousness and postural tone that results from a sudden decrease in cerebral perfusion.

Okay so let's unpack that because every single word in that definition matters.

A lot.

All right let's start with the first word.

Transient.

What does that really mean in this context?

Transient means it resolves on its own.

It's temporary

and crucially self -limiting.

The body fixes it.

So if you have to intervene.

If you have to do CPR or if they require some kind of medical intervention to wake them up that wasn't syncope that was cardiac arrest or something much more severe.

Got it.

Syncope is by definition a self -correcting problem.

The problem causes a change falling down that then fixes the problem.

Okay that's a key distinction.

Next part of the definition loss of postural tone.

That just means gravity wins.

The muscles that are constantly firing to keep you upright they just they stop receiving signals from the brain.

So you go limp.

You go limp.

You fall down or you slump over.

The posture is lost.

And finally the last part of that definition.

Decrease in cerebral perfusion.

The This is the physiological why.

The brain is an incredibly demanding organ.

It has no backup battery.

No energy reserves.

It requires a constant second by second stream of oxygenated blood.

So it's very needy.

Very needy.

And if that fuel line gets cut off for even a few seconds the tech says usually about eight to ten seconds is all it takes.

The lights go out.

Consciousness is lost.

That's a shockingly short amount of time.

It is.

It shows you how dependent the brain is on that constant flow.

And the text makes a really really big point right up front about what syncope is not.

It seems like ruling out the the imposters is step one.

It is absolutely step one.

Correct.

It is distinct from coma for example.

A coma is a prolonged persistent state of unconsciousness.

Syncope is as we just said transient.

It's brief.

Okay and then the big one seizures.

Yeah this is the trickiest differential we're going to talk about today because a seizure can sometimes look like fainting.

And to make things more confusing fainting can sometimes look a little like a seizure.

We'll have to dig into that more later.

We will.

But the underlying mechanism is totally different.

A seizure is an electrical storm in the brain.

Syncope is a power outage.

That's a great way to put it.

An electrical storm versus a power outage.

It also says it's distinct from shock.

Right.

In shock the blood pressure is dangerously low.

The whole body is under perfused.

But the patient might still be awake or at least semi -conscious.

They're not necessarily out cold in the way they are with syncope.

And importantly it's distinct from vertigo.

Yes.

This is a common point of confusion for patients.

Vertigo is a hallucination of movement.

The room is spinning or you feel like you're tumbling through space.

But you're still you're still there.

You're conscious.

You're conscious.

You're miserable but you're conscious.

If a patient says I felt like I was spinning and then I fell because I lost my balance.

That's a vestibular issue.

An inner ear problem.

As opposed to?

As opposed to I was walking across the kitchen and the next thing I knew I was waking up on the floor.

That lights out moment.

That gap in time.

That is the key to syncope.

Okay so the text drops some epidemiology on us right away to kind of set the stage.

It says about 10 percent of adults will experience this at some point.

Which is a huge number.

That's one in ten people.

It's very very common.

But the incidence curves are what you really need to pay attention to as a clinician.

The pattern is what matters.

What's the pattern?

It spikes in the teens and 20s.

This is usually the benign vasovagal stuff fainting at the site of blood.

That sort of thing.

And then the incidence increases and the text uses the word exponentially after age 70.

Exponentially.

Wow.

So age is a massive context clue.

A faint in a 20 year old means something profoundly different than a faint in an 80 year old.

Your whole diagnostic algorithm shifts based on that one piece of data.

And interestingly the text notes it's pretty rare in children.

Which is a fantastic clinical pearl to remember.

The text says that unless there's a very specific trigger, like a known seizure disorder, a cardiac arrhythmia, or what those breath holding incidents will talk about, kids usually don't just drop from syncope.

If a healthy six year old faints while running on the playground,

your alarm bell should be ringing at maximum volume.

That's not normal.

That is not normal.

Whereas if a 15 year old faints in a hot crowded church service,

well that's almost a physiological cliche.

Right.

Okay.

So this brings us to the mission for this deep dive.

The text sets up what it calls a clinical mission.

Since patients are always seen after the event, our goal is to rule out the serious causes.

Through a careful history and physical exam.

Right.

And the text explicitly says we want to avoid relying heavily on expensive tests right out of the gate.

That is the art of primary care.

Right there.

You can order a million dollar workup.

You can order MRIs, tilt tables, endless cardiac monitoring, genetic testing.

You can throw the kitchen sink at it.

You can't.

But the answer, probably 80 % of the time,

is in the story the patient or the witness tells you.

We just need to distinguish between benign syncope, like a vasovagal response, and life -threatening syncope.

Which is usually...

Usually cardiogenic.

Yeah.

It's coming from the heart.

And even the benign syncope has risks, right?

I mean, it's not just about the heart stopping.

The fall itself is a problem.

Absolutely.

This is a critical point.

Even if the physiological cause is totally benign, say they just got a little overheated, the physics of the fall are not benign.

Right.

If you lose consciousness while you're walking down a flight of concrete stairs or while you're operating heavy machinery...

Or driving a car.

Or driving a car, the consequences can be fatal.

In an elderly person, a benign faint that leads to a hip fracture can be the start of a cascade of decline that ends their independence.

You always have to be thinking about fall risk.

Always.

It's part of the equation, regardless of the underlying cause.

Okay.

Let's move into the first big section.

Diagnostic reasoning, the focused history.

The text presents this as a series of key questions, which I find really helpful.

It's a great framework.

And the very first hurdle is, is it really syncope?

Did this event even qualify?

Right.

Because patients use such vague language, they'll say, I blacked out or I had a spell, I got dizzy, I had a turn.

You have to clarify what blacked out means.

You do.

Does it mean your vision went dark, but you were still standing?

Or does it mean you lost time?

So the first question the text suggests is simply, did you lose consciousness?

Pin them down on that.

And if they say yes, the next question is for how long?

And the text gives us a very specific timeframe here, which I found really useful clinically.

It says episodes of syncope lasting longer than 10 minutes are rarely physiologic syncope.

10 minutes?

That's a long time to be unconscious.

A very long time.

The body's reboot mechanism is usually much, much faster than that.

Remember, syncope happens because blood flow to the brain drops.

When you fall flat, gravity helps you and blood flow returns.

You should wake up.

If someone is out for 15 or 20 minutes, you're looking at something else.

Like what?

Neurologic issues, a severe metabolic crash, or a cardiac arrest where they were down for a while before their heart restarted.

But simple syncope.

You're usually awake in under a minute or two once you're horizontal.

Okay.

The text also talks about differentiating dizziness and something it calls presyncope.

Presyncope is that feeling of I'm about to pass out,

but you don't actually lose consciousness.

The room starts to close in.

You hear a ringing in your ear.

Exactly.

The tunnel vision, the muffled hearing, feeling sweaty and clammy.

You know you're going down, but you manage to grab a chair or lie down before you lose consciousness completely.

And that distinction is vital.

It is because dizziness and vertigo don't involve that impending loss of consciousness.

But presyncope often shares the exact same causes as syncope.

It's just that the brain didn't quite run out of fuel completely.

The event was aborted.

Okay, so once we've established it was likely a true loss of consciousness, we move on to the prodrome.

A fancy way of asking.

What happened right before the fall?

What were the warning signs?

The text lists some classic ones.

Sweating, nausea, and yawning.

Yes, yawning.

That one stuck out to me.

Why yawning?

It's a fascinating and very specific sign of vagal activation.

The vagus nerve is a huge nerve that controls a lot of our rest and digest functions, and it's kicking into overdrive.

Yawning is one of those weird parasympathetic responses it can trigger.

So if a patient tells you, you know, it was weird, I started yawning uncontrollably, felt really hot, and then I woke up on the floor.

You could almost diagnose invasive vagal syncope right there in that sentence.

It's a huge clue.

It tells you the autonomic nervous system was the culprit.

Now,

contrast that with the other warning signs the text mentions for things that aren't simple syncope.

Right.

So if the patient describes an aura, and we have to be specific here, an aura isn't just feeling weird.

It's a specific smell that isn't there, like burning rubber.

Or flashing lights.

Or zigzag lines in their vision, or a powerful sense of deja vu, like I've lived this exact moment before.

That points directly to the brain, specifically the temporal lobe.

That's a seizure.

And tongue biting.

Yes.

And the location of the bite is really important here.

So not just if they bit it, but where?

Exactly.

In a seizure, the jaw clamps shut violently and rhythmically.

They often bite the side of the tongue, the lateral aspect.

In a simple faint, if they bite their tongue at all, it's usually just the tip from the impact of their chin hitting the floor.

But lateral tongue biting, that is highly specific for a tonic -clonic seizure.

That's a great clinical pearl.

What about the precipitating factors, the pre -event characteristics?

This seems like where the real detective work comes in.

It is.

You have to ask, with excruciating detail, what exactly were you doing the second before this happened?

The text is very specific.

It says loss of consciousness triggered by pain, exercise, urination, or defecation is likely not a seizure.

Correct.

Those are all classic situational triggers for syncope.

They all involve messing with the autonomic nervous system.

So if someone stubs their toe really hard, just agony -level pain, and passes out, that's likely syncope.

Exactly.

Pain is a massive trigger for the vagus nerve.

It can cause that sudden precipitous drop in heart rate and blood pressure.

It's a protective mechanism in a way.

The text also mentions breath -holding spells in children.

Ah, the ultimate temper tantrum.

Right.

In a way, yes.

But medically, it's a specific form of syncope.

The child gets angry or hurt.

They let out a huge try, hold their breath at the end of it.

And turn blue.

They turn blue, go silent, and then go limp and pass out.

It is absolutely terrifying for parents to witness.

It looks like their child is dying.

But it's technically a reflex event, not a seizure and not dangerous in itself.

Another key factor the text points to is diet.

You have to ask when they last ate or drank.

So important.

Fasting or dehydration points you directly toward reflex syncope.

If the tank is empty, if their blood volume is low, it takes very little to drop the pressure enough to cause a faint.

The classic story of the student who skipped breakfast and lunch and then stood in a hotline for an assembly.

And down they go.

It's almost a guaranteed recipe for syncope.

Now here is a red flag the text highlights that I have to admit terrified me a little bit.

It's syncope that occurs without any warning symptoms.

That is the single biggest red flag in the entire history.

Why?

If a patient says, I was just walking across the room feeling totally fine.

And the next thing I knew I was waking up on the floor with no nausea, no sweating, no dizziness beforehand.

No prodrome at all.

Zero prodrome.

That suggests a primary cardiovascular origin.

It suggests the heart just stopped providing flow instantaneously.

It's like a light switch being flipped off.

Because with the more benign stuff, the body usually gives you a heads up that the pressure is dropping.

Exactly.

That fading out feeling, the tunnel vision, the muffled hearing.

That is your brain telling you that the blood pressure is slowly tanking.

Yeah.

It's a gradual process.

But if there's no fade out.

If there's no fade out, it means the pump stopped or the rhythm scrambled instantly into something non -perfusing.

Like ventricular tachycardia.

That requires a very different, very urgent workup.

Okay.

Let's look at the event itself and what happens after.

The post -event characteristics.

How do we tell a seizure from a faint just by looking at the fall itself?

Well, the classic sign of a seizure is rhythmic movements of the extremities, the shaking or jerking.

However, and the text notes this, this is a major pitfall.

What is?

Those movements can happen in syncope.

We call it convulsive syncope.

Wait, so you can faint and still twitch.

That seems incredibly confusing.

It is.

It's due to brain hypoxia.

When the brain is starved of oxygen, even for a few seconds, the motor cortex can get irritable and misfire.

So how do you tell the difference?

The duration and character.

In convulsive syncope, it's usually just a few brief unsustained jerks as they go down.

If the rhythmic jerking goes on for a minute or more, that's a seizure.

If it's two or three big twitches and then they are completely still and limp, it could just be the faint.

And the recovery time, how does that help?

This is often a much stronger differentiator.

In simple syncope, once you are flat on the floor, gravity is no longer fighting you.

Blood rushes back to the brain and you wake up relatively quickly and are clear -headed.

You know who you are, where you are.

Great.

You might be tired or embarrassed, but you know what's going on.

In a seizure, there is almost always a postictal state.

Postictal after the event.

Correct.

The brain has just run an electrical marathon.

The patient is profoundly confused, disoriented, maybe combative.

And this can last for five, 10, even 30 minutes or more.

So if they wake up and immediately say, oh, man, why am I on the floor?

That's a point for syncope.

Generally, yes.

If they just look at you blankly for 20 minutes and don't know their own name, that's a big point for seizure.

A very big point.

That return to baseline speed is a critical data point you need from a witness.

Also, the text mentions those pediatric specifics again, cyanosis, the clonic jerks, and something called opus adenos.

What's that?

It's a severe, rigid arching of the back.

It's a dramatic posture.

Those are associated with breath -holding spells, which again can look a lot like a seizure, but are physiologically distinct.

Okay.

This feels like a good place to shift to section two.

The text has this great section on evidence -based practice, and it's basically a scorecard, a comparison chart for cardiac versus non -cardiac predictors.

I love these kinds of lists.

They help you sort your patient into a high -risk or low -risk bucket almost immediately.

Which is really what primary care is about so much of the time.

It's 90 % of the job.

Who can I safely manage and send home?

And who needs to go to the ER right now?

So let's pan a picture of the high -risk cardiac cause patient.

According to the text, who is this person?

Okay.

First demographics, age greater than 60.

Check.

Male sex.

The plumbing is just older.

The risk of underlying coronary disease is higher.

Makes sense.

Then their past medical history,

known is ischemic heart disease, structural heart disease, or reduced ventricular function.

That's heart failure.

So if they have a bad heart already,

a previous heart attack, heart failure,

cardiomyopathy.

And then they faint.

You have to assume it's the heart acting up until proven otherwise.

You don't get to assume the guy with a 20 % ejection fraction just got dehydrated.

The heart is guilty until proven innocent.

And the prodrome we talked about, how does that fit in?

A brief prodrome, or even better, no prodrome.

The light switch.

The light switch.

Or maybe palpitations right before the drop.

My heart started racing or fluttering and then I was out.

But not that long,

drawn out.

I don't feel so good.

I need to sit down, kind of build up.

And the situation, the context of the faint.

Occurring during exertion is a massive, massive red flag.

We'll talk more about that specifically later.

Or, and this is a critical one, syncope, while supine.

While lying down.

Yes, while lying down.

That seems impossible.

How can you faint if you're already lying flat?

Exactly.

Think about the physics.

If you faint while you're standing, it's often gravity pulling blood away from the brain and into your legs.

If you faint while you are already lying down, gravity isn't the problem.

The pump is the problem.

A healthy person essentially cannot have vasovagal syncope while lying down.

It has to be an arrhythmia or a cardiac standstill.

That makes total sense.

That's a huge red flag.

And then obviously an abnormal cardiac exam on your physical.

Or a family history of sudden cardiac death.

Especially under the age of 50.

If their brother or father dropped dead at 45, you have to worry about genetic heart conditions.

Okay, now let's flip the coin.

Let's look at the non -cardiac or allure risk profile.

Who is this patient?

This is a younger patient.

No known history of cardiac disease.

And the event happens only when they are standing or changing positions quickly.

Like going from lying down in bed to standing up.

A classic head rush.

Exactly.

Orthostatic stress.

And they have a strong classic prodrome.

The nausea, the warmth, the sweating.

Yes.

The text also lists specific triggers.

A painful or distressful stimulus being in a medical environment.

Fainting at the sight of a natal.

The classic.

Or situational triggers like a severe coughing fit.

Laughing really hard or using the toilet.

And what about their history of fainting?

If they have a long history.

Years and years of frequent recurrence with the exact same characteristics.

If they tell you, oh yeah, I've been fainting like this since I was 15 and I'm 40 now.

It's very unlikely to be a new deadly heart condition.

It's just how they're wired.

It's their particular flavor of syncope.

That's actually pretty reassuring.

Now moving on to section three.

The witness factor.

The text makes a really practical point here that is so true.

The patient is a poor historian.

They're a terrible historian.

And it's not their fault.

They were unconscious.

They literally missed the main event.

They can tell you everything that happened before and they can tell you what it felt like to wake up on the floor.

But the during is a complete black hole in their memory.

So we need a witness.

The witness is gold.

You always, always want to get the witness on the phone if they aren't in the room with the patient.

What do you ask them?

You ask them what the patient looked like.

Did they turn pale as a sheet?

Did they turn blue?

Were their eyes open or closed?

Did they make any sounds?

And most importantly, was there any jerking?

And if so, for how long?

How long were they out?

All the things the patient can't possibly know.

Exactly.

The text also notes a fascinating pattern, especially with adolescents.

Those with psychogenic syncope,

meaning it has a psychological or psychiatric origin, usually have an audience for the event.

Ah, the traumatic faint in the middle of a school assembly.

It happens.

If it only ever happens when friends are watching or during a stressful family argument, but never when they're alone in their room,

that's a data point.

It doesn't mean they're faking it though.

No, absolutely not.

The stress is real and the physiological response is real.

But it points you away from a cardiac arrhythmia and more toward a conversion disorder or panic attack.

Let's talk about immediate referrals.

We're in a primary care setting.

But when do we need to stop everything and send this patient to the ER or to a cardiologist immediately?

The text lists some key questions for this.

We're looking for structural heart disease.

The text lists coronary artery disease and congestive heart failure, or CHF.

Patients with these conditions who have a syncopable event have a very high risk of sudden death in the next year.

The mortality rate is significantly higher in that group.

They cannot be sent home.

They need to be admitted and monitored.

The text also mentions specific structural issues like aortic or mitral stenosis.

Right.

Think of this as outflow obstruction.

It's a plumbing problem.

If the main valve leading out of the heart, the aortic valve, is tight and calcified, the heart literally can't pump enough blood out to the brain.

Especially during exertion.

Especially during exertion when the muscles are demanding all the blood flow.

That is a mechanical problem that needs fixing, often with valve surgery.

If you have known aortic stenosis and you start fainting, that is a very, very bad prognostic sign.

And conduction issues.

Problems with the heart's wiring.

Complete heart block.

If the electrical signal isn't getting from the top chambers of the heart, the atria to the bottom chambers, the ventricles, the heart rate can drop to 30 or 40.

That's not enough to keep you conscious.

Also, the text notes that children with a history of cardiac surgery are at high risk for arrhythmias later in life.

The scar tissue on the heart from the surgery disrupts the normal electrical pathways.

The text gets really specific about palpitations and arrhythmias here.

It mentions SVT or superventricular tachycardia and ventricular tachycardia.

It notes that ventricular tachycardia or VT with a rate of 200 beats per minute might be asymptomatic in some young healthy people, but it very often causes syncope.

Why?

It seems like a fast heart rate should mean more blood flow.

It's too fast.

The heart is beating so rapidly it doesn't have time to fill with blood between beats.

If it doesn't fill, it can't pump anything out.

It's dry pumping, effectively.

No output, no blood to the brain.

And the worst case scenario, arrhythmia.

That would be chaotic ventricular activity, what we call ventricular fibrillation.

That is not a perfusing rhythm at all.

That is fatal within minutes without defibrillation.

So in that case, syncope is?

In that case, syncope is essentially an aborted sudden death.

The rhythm went into V fib, they passed out,

and then it spontaneously corrected itself just in time.

You do not want to bet on it correcting itself the next time.

That's terrifying.

And then there's the combination of fainting with chest pain or dyspnea, shortness of breath.

If syncope comes with chest pain or shortness of breath, you have to think about major mechanical blockages.

A pulmonary embolism, a PE,

a big clot in the lung can acutely block blood flow through the heart.

And a heart attack.

Or a heart attack, a myocardial infarction.

The pump is failing because its own blood supply is cut off or the pipes are clogged.

These are absolute emergencies.

This leads perfectly into section four where we talk specifically about exertion.

The text has a pretty hard and fast rule here that we should all remember.

The rule is syncope during or immediately after exercise should be considered to be of cardiac origin until proven otherwise.

Until proven otherwise.

So you have to assume the worst.

You have to.

Exertional syncope is one of the most dangerous presentations.

It suggests the heart cannot meet the body's demand for blood flow when it's needed most.

However, the text does offer one crucial exception, or at least a distinction,

regarding the timing.

What's that?

The difference between syncope during exertion versus after exertion.

Ah, okay.

Syncope after exertion in a well -trained athlete who has no underlying heart disease might be vasovagal.

So why does that timing matter so much?

Mid -sprint versus after crossing the finish line.

It comes down to physiology.

Yeah.

During intense exercise, your big leg muscles are acting as a secondary pump.

Every time they contract, they squeeze the veins and push blood back up to the heart.

It helps with venous return.

A lot.

At the same time, your blood vessels are wide open, they're vasodilated, to get as much blood to those working muscles as possible.

Now, imagine you cross the finish line of a marathon and you just stop dead.

The muscle pump in your legs instantly stops working.

But your blood vessels are still wide open.

So the blood just pools in your legs.

It pools in your legs, venous return to the heart plummets, cardiac output drops, and you faint.

That's post -exercise collapse.

It's mechanical.

But if they drop mid -sprint?

If they drop mid -sprint, the muscle pump was working just fine.

That means the primary pump, the heart, must have failed.

That suggests something like hypertrophic cardiomyopathy or a life -threatening arrhythmia triggered by adrenaline.

That's the athlete collapsing on the soccer field that we see on the news.

That is the one.

And that is always an emergency.

Got it.

Mid -exercise equals extreme danger.

Post -exercise equals possibly benign mechanics, but you still have to check it out thoroughly.

Exactly.

You still get them a full cardiac workout.

Now, what about headaches?

The text has a question.

Do you have headaches?

Why is that relevant?

They're connecting migraines to syncope.

It seems that the intense pain of a migraine and its effect on the brain stem can actually trigger a vasovagal response and cause syncope.

That's interesting.

So how do we differentiate that from, say, someone who fainted for another reason, hit their head, and now has a headache?

That's the key question to ask.

The text says to verify that the headache isn't from the trauma of the fall.

But usually, with a migraine -associated faint,

the classic migraine headache continues after they wake up.

And they'll have the other migraine symptoms.

Right.

The photophobia sensitivity to light the nausea, maybe a visual aura beforehand, and a family history of migraines.

The text also mentions other visual symptoms, like diplopia.

Diplopia is double vision.

That suggests something more neurological is going on, like a TIA, a transient ischemic attack, or a very complex migraine affecting the brain stem.

Why the brain stem?

The brain stem is what controls the alignment of your eyes.

So if you're seeing double, it's a sign that that part of the brain is involved.

That moves you away from a simple faint and much more toward needing a neurology consult.

Okay, I want to pause here for a second because there's a really cool evidence -based practice box in the text about the Valsalva maneuver.

Yes.

I feel like we all learn about this in school, but the text gives some really specific details on its efficacy for stopping SVT.

Right.

SVT superventricular tachycardia is a common type of rapid heart rhythm that can sometimes be stopped by stimulating the vagus nerve.

And the vagus nerve acts like a break on the heart rate.

And the maneuver it describes isn't just bearing down like you're having a bowel movement.

No, it's more standardized than that.

The text describes a specific protocol based on research.

Having the patient blow into a 10 -milliliter syringe while lying down or prone for 15 seconds.

Blowing into a syringe, that's to provide a standard amount of resistance.

Exactly.

You tell them to try and blow the plunger out.

It generates a consistent amount of increased pressure within the chest cavity.

The intra -thoracic pressure.

And that's what triggers the vagus nerve.

That pressure change triggers a baroreceptor reflex that then fires the vagus nerve, which can terminate the arrhythmia.

So the big question, does it actually work?

The text cites a systematic review of three different studies.

The reversion rates,

the success rates for converting the rhythm back to normal, were between 19 .4 % and 54 .3%.

So it works maybe half the time at best.

That doesn't sound amazing.

But think about it, for a completely non -invasive, zero -cost intervention that you could do right there in the clinic room, that's actually pretty good.

That's a good point.

If it works, you've just saved that patient a trip to the ER and a dose of IV adenosine, which is a famously miserable drug to receive.

Patients say it feels like they're dying for a few seconds.

And is the maneuver safe?

Generally, yes.

The text notes the potential side effects could be hypotension or, ironically,

syncope.

So you could make them faint while trying to stop their heart from racing.

It is possible you were messing with blood pressures.

But the studies that were reviewed in the text reported no significant side effects.

Moving on to section five, situational and environmental triggers.

We've touched on vasovagal syncope, but let's get into the mechanism the text describes.

This is the common faint.

Right.

The text calls it neurocardiogenic.

It's a reflex, a miscommunication between the heart and the brain.

Triggers like stress, fear, fatigue, or being in a hot, crowded room cause two things to happen simultaneously.

What are they?

First, peripheral vasodilation.

Your blood vessels, especially in your legs, open up wide.

And second, bradycardia.

Your heart rate slows down, sometimes dramatically.

That is a terrible combination if you're trying to keep blood in your brain.

It's the worst possible combination.

Usually, if your blood vessels open up, your heart should speed up to compensate and keep the pressure stable.

Here, the wires get crossed.

So the pressure just bottoms out.

The text says, lack of muscle activity prevents venous return.

The blood pools in your legs, the heart slows down, and the brain says good night.

And the cure of gravity suddenly starts working for you instead of against you.

Precisely.

The second you become supine or horizontal, venous return is restored.

The heart fills up with blood again.

It pumps that blood to the brain and the patient wakes up.

It's a beautiful, if dramatic, reboot mechanism.

The text warns about standing them up too quickly afterward, which can cause a recurrence.

Yes.

If you prop them up in a chair right away, the vessels are probably still dilated, the system hasn't reset yet, and down they'll go again.

You have to let them lie flat for a few minutes.

What about these very specific types, post -tusive and post -micturition syncope?

Post -tusive is syncope that happens after a severe bout of coughing.

A paroxysm of coughing dramatically increases that intra -thoracic pressure, just like the Valsalva we were talking about, and it can physically block blood from returning to the heart.

No return, no output, no blood to the brain,

and post -micturition.

This is fainting after or during urination.

The text explains that the act of emptying a full bladder causes a sudden release of intravascular pressure.

How does that work?

Well, a full bladder puts pressure on everything around it.

When you empty it, that pressure is gone, and it can trigger both vasodilation and a vagal response that causes bradycardia.

So you pee, the pressure drops, the vessels open, the heart slows down, and you faint.

It's a classic presentation, especially in older men who get up in the middle of the night.

They get up, they're warm from being in bed, they might strain a little bit, start to stream, they empty the bladder, and they drop.

Okay, let's talk about section six, medications and chronic conditions.

I was really surprised by the statistic here.

Ten percent of all syncopal episodes are caused by medications.

It's a huge number, and it's so important.

We always have to check the med list.

If you don't look at the meds, you will miss the easiest fix on the entire differential.

So who are the usual culprits on that med list?

The text lists a few big categories.

Antidepressants, especially the older tricyclic ones.

Yeah.

Antiarrhythmics, which by design alter heart function.

Beta blockers, which slow the heart rate down.

And diuretics.

And diuretics, which make you lose fluid and can lead to dehydration and low blood volume.

It's easy to see how those could cause problems.

Beta blockers block the body's normal response to low pressure, right?

Exactly.

If you stand up, your BP starts to drop, your heart should race to compensate.

If you're on a beta blocker, it can't.

The signal to speed up is blocked.

It's stuck in low gear.

What about recreational drugs?

Alcohol is a big one.

It's a vasodilator and a diuretic, so it's a double threat.

Cocaine can cause coronary artery spasms and life -threatening arrhythmias, but the text points out a very specific one for adolescents.

Amyl nitrite or butyl nitrite.

Those are often called poppers, right?

Yes, often sold as aphrodisiacs or muscle relaxants.

Their entire purpose is to cause intense, immediate vasodilation.

So it's not a side effect, it's the intended effect.

It's the intended effect.

But if you dilate all your blood vessels at once, your blood pressure will absolutely bottom out and you will faint.

So if a young person comes in with unexplained syncope, you have to be willing to ask the awkward questions about substance use.

You have to.

And for young children,

the text makes a great point about accidental ingestion of a family member's medication.

That should always be on your mind if a toddler comes in with unexplained syncope or lethargy.

Right.

Do they get into gremulous blood pressure pills?

Under chronic health conditions, the text brings up diabetes.

Right, for hypoglycemia.

Low blood sugar can cause a loss of consciousness.

It's usually more of a gradual slide than the sudden drop of cardiac syncope, but it's definitely on the differential.

You have to check a finger stick glucose.

And pregnancy is a risk factor.

A huge risk factor for orthostatic hypotension.

The pregnant uterus can compress the major veins in the abdomen, especially the vena cava, which impedes blood return to the heart.

And the hormones.

The hormonal changes of pregnancy also cause vasodilation.

So it's a perfect storm for fainting, especially on standing up quickly.

Section 7 in our outline covers the unusual suspects.

These are the things we might miss if we aren't careful.

Let's go back to psychogenic syncope for a moment.

We mentioned the audience factor earlier, but the text adds some more specific clinical clues to look for if you suspect it.

These patients often have very frequent dramatic episodes, but a completely normal cardiac workup.

How do you spot it if you're lucky enough to witness the event?

The text notes unpredictable motor reflexes, but a lack of pathological reflexes.

This is key.

Their vital signs and appearance are normal during the faint.

So they claim to be unconscious, but their blood pressure is 120 over 80 and their pulse is 70.

Exactly.

And their skin color is normal.

True syncope almost always comes with pallor.

The white is a sheet look because the blood is draining from the head.

If they're rosy cheeked and their pulse is strong and regular, they are not having physiologic syncope.

What about carotid sinus hypersensitivity?

That sounds obscure.

It's an interesting one.

It's triggered by pressure on the carotid sinus, which is a little pressure sensor in the carotid artery in your neck.

And it's hypersensitive.

Right.

In some people, especially older men, this sensor is too sensitive.

So sudden head rotation, looking over your shoulder or wearing a tight shirt collar, can put pressure on it.

And the sensor tells the brain the blood pressure is too high.

It sends a false signal to the brain saying, emergency, pressure is way too high.

And the brain responds by slamming the brakes on the heart rate, causing profound bradycardia or even a brief pause, and they pass out.

So the classic story of the guy wearing a tight tie who turns to look at a car and just drops.

That's the classic scenario.

Or an elderly man who passes out while shaving his neck.

The text also lists some infectious or inflammatory histories to ask about.

Kawasaki disease.

This is a pediatric condition.

If a child had Kawasaki disease in the past, they were at a lifetime risk for coronary artery aneurysms and ischemic heart disease.

So chest pain or syncope with exercise, indicated with that history, is very, very serious.

And Lyme disease.

Lyme disease can directly affect the heart's conduction system.

It can cause heart block.

It's called Lyme carditis.

So if you're in an area where Lyme is endemic and someone has unexplained syncope, you have to think about it and check for history of a tick bite or a rash.

Finally, family history.

We touched on this, but the text gets even more specific, saying to ask about sudden death or MI before age 30 in the family.

That age is key.

Sudden death at 80 is sad, but often expected.

Sudden death at 28 is a tragedy and suggests a genetic cause, like a cardiomyopathy or a channelopathy, an inherited problem with the heart muscle or its electrical ion channels.

And it mentions prenatal lupus.

How does that connect?

This is a very specific one.

If the mother had lupus while she was pregnant, the antibodies can cross the placenta and attack the developing baby's heart, causing congenital heart block.

So you might ask the parent of a child with syncope about the mother's health during the pregnancy.

It's a deep dive connection.

Okay, we have the history.

We've been a detective.

Now we actually put our hands on the patient.

Section eight, the focused physical examination.

Where do we start?

Vitals.

Always start with vital signs, specifically orthostatic vital signs.

You have to measure their blood pressure and pulse while they're lying down, then sitting, then standing.

And you can't rush it, right?

You have to wait between measurements.

You absolutely have to.

You need to let the blood pool.

The standard is to wait at least two to three minutes after they stand up before you take the standing blood pressure.

What officially counts as a positive finding for orthostatic hypotension?

The text defines it as a systolic drop of at least 20 millimeters of mercury or a diastolic drop of 10, or just as importantly, if their symptoms are reproduced.

So even if the numbers don't quite hit that 20 -point drop, if they say, whoa, I'm getting dizzy.

I feel like I'm going to pass out.

That's a positive test.

That's diagnostic.

But for their pulse, what are we looking for?

We're looking for the extremes.

Profound bradycardia, a heart rate less than 35 or 40, is not enough to maintain cerebral perfusion.

On the other end, the text says tachycardia up to about 180 is usually tolerated in a healthy heart, but obviously that's not normal and needs investigation.

It also says to compare the blood pressure in both arms.

Why is that?

A significant difference in blood pressure between the two arms suggests a large vessel blockage like subclavian steel syndrome or in an emergency, an aortic dissection.

It points you toward a major cardiac or vascular cause.

If the left arm is 20 -80 and the right arm is 80 -50, you have a serious plumbing problem somewhere.

Moving on to the body systems exam.

Hydration status is obvious, but for the cardiac exam, what are we listening for and palpating for?

You're feeling for lifts or heaves on the chest wall, which suggests the heart is enlarged.

And the text mentions a specific dynamic maneuver, the squat to stand test.

What is that there?

You have the patient squat down and you listen to their heart with your stethoscope.

Then you have them stand up quickly and you keep listening.

This maneuver changes the volume of blood returning to the heart.

Squatting increases venous return, standing decreases it.

Exactly.

And certain murmurs change dramatically with this.

Specifically, the systolic ejection murmur of hypertrophic cardiomyopathy, a dangerous cause of syncope in athletes, gets much louder when they stand up.

We're also listening for specific heart sounds.

A loud S2 heart sound,

the presence of an S3 gallop, which can indicate heart failure and fluid overload, or any carotid brutes, those whooshing sounds in the neck arteries that imply a blockage.

And then neurologic exam.

What are the key components there?

A basic check of mental status,

cranial nerves, and the Romberg test, having them stand with their feet together and close their eyes to check their balance.

And checking their gait.

Absolutely.

You want to see if there are any subtle focal neurological deficits that might suggest a stroke or a brain tumor is the cause.

If they faint and also have a new droopy eyelid or weakness on one side, that is not vasovagal syncope.

Section 9 brings us to laboratory and diagnostic studies.

The text starts with a rule of thumb about blood work that I think is really important.

It says that routine blood tests like electrolytes, glucose, a CBC, are rarely useful for the workup of syncope unless a seizure is strongly suspected.

So don't just shotgun a bunch of labs on every patient who faints.

Exactly.

Unless your history points you toward thinking they're diabetic and had a hypoglycemic event or they're anemic from a GI bleed, the diagnostic yield of those labs is extremely low.

You're mostly just wasting money in the patient's time.

But cardiac testing, on the other hand.

That is the gold standard for a syncope workup.

And the 12 -lead ECG is the absolute first line.

Almost every patient with true syncope should get an EKG.

What are we looking for on that little piece of paper?

A whole host of things.

Conduction disorders like heart block,

evidence of a prior heart attack, like Q waves,

signs of abnormal coronary artery placement, and a prolonged QT interval, which is a setup for a potentially fatal arrhythmia called dorsazda point.

If that initial ECG is normal, but we still have a high suspicion for an arrhythmia, what's the next step?

Monitoring.

The text does a good job distinguishing between a holter monitor and an event or loop monitor.

What is the difference between them?

A holter monitor is typically for 24 or 48 hours.

It records every single heartbeat continuously.

It's great if the patient is having symptoms every single day.

But if they only faint once a month.

A 24 -hour holter will almost certainly miss it.

You have a very low chance of catching the event.

So that's when you use the loop monitor.

Right.

An event or loop monitor is designed for long -term wear for weeks or even up to 30 days.

It's much better for catching these transient, infrequent events.

And the loop monitor can be patient -activated, right?

Yes, that's the genius of it.

The patient faints, they wake up and they press a button on the device.

The monitor then remembers the heart rhythm from the last few minutes because it's always recording on a short loop.

It essentially time travels backward to record what the heart was doing while you were passed out.

What about the tilt table test?

We hear about this a lot for fainting.

It's used for cases of unexplained syncope to try and provoke a vasovagal response under controlled conditions.

You strap the patient safely to a table and then you tilt them upright to about 70 degrees and just leave them there.

To see what happens.

To see what happens.

A positive result is if their blood pressure and heart rate drop and they reproduce their symptoms, it confirms they have that neurocardiogenic wiring.

It's helpful when you've ruled out all the scary heart stuff but still don't have a clear answer.

Section 10 brings us to the end with the differential diagnosis tables.

The text provides these great summaries to kind of consolidate all this knowledge.

Let's do a quick fire recap of the common profiles.

Let's do it.

Profile 1, the cardiac cause.

History of shortness of breath, chest pain, palpitations, or fainting with exertion.

On exam, you find murmurs, lifts, or a loud S2.

Your first action is ECG, then probably a holter or an echo.

The urgency is high.

Profile 2, the neurocardiogenic or vasovagal type.

Triggered by emotional events, crowded rooms, prolonged standing.

They have that classic prodrome of nausea and warmth.

The physical exam is usually completely normal.

Your action is reassurance, education, and hydration.

Profile 3, breath holding in a child.

History of getting angry or hurt, letting out a cry, then silence, and then they drop.

On exam, you might see cyanosis, they look blue, or pallor.

The action is reassurance for the terrified's parents.

Profile 4, orthostasis.

The history is fainting right after a position change, or a background of pregnancy, prolonged bed rest, or diuretic use.

The key finding is that 20mm of mercury drop in systolic blood pressure on your orthostatic testing.

The action is a medication review, increasing fluids and salt, maybe compression stockings.

And finally, profile 5, the neurologic or psychiatric causes.

For a migraine, you'll have a history of photophobia and nausea.

For a seizure, incontinence and that postictal confusion are key.

For what the text calls hysterical syncope, you have an audience present, a gentle, non -injurious fall, and often perfect memory of the event.

That perfect memory is a dead giveaway, isn't it?

It really is.

If they can describe in detail the pattern on the ceiling tiles as they were falling, they probably weren't fully unconscious.

This brings us to the outro.

We have covered a huge mound of ground.

What is the clinician's mindset summary here?

How do we put this all together?

You start with a history.

It is 90 % of your diagnosis.

You listen to the story.

Then you rule out the hard first.

Always, because that's what kills people.

Check the meds.

Always check the meds, because that's the most easily fixable cause.

And then use your physical exam to confirm the triggers you suspect from the history, like orthostasis.

And there's a final thought from the text that I found both somewhat comforting, but also a little frustrating as a clinician.

The unknown causes.

Yes.

The text notes that for about one third of all syncopal episodes, even after a full and thorough workup, the cause remains unknown.

We never find it.

And is that a diagnosis in itself?

Syncope of unknown origin?

It is.

If you have done your due diligence and ruled out all the bad stuff, the heart is structurally normal, the EKG is fine, the neuro exam is fine, then sometimes that is the final answer.

And the good news is, the prognosis for that group is generally very good.

It's frustrating for the detective in us, but it's actually good news for the patient.

Well, on that mysterious but reassuring note, we will wrap up this deep dive into syncope.

It's a symptom, not a disease, and it's up to you, the clinician, to find the cause.

Keep your ears open for the details of the history, and keep your eyes open for those red flags.

Thank you from the Last Minute Lecture Team.