Chapter 12: Drugs for the Treatment of Heart Failure

The text details the pathophysiology of heart failure, distinguishing between systolic dysfunction, defined by reduced contractility, and diastolic dysfunction, characterized by impaired relaxation and filling. A central theme is the maladaptive process of cardiac remodeling, driven by neuroendocrine activation including the renin-angiotensin-aldosterone system and the sympathetic nervous system, which leads to ventricular dilation, hypertrophy, and fibrosis. Pharmacotherapy is categorized into agents that improve symptoms and those that prolong survival by attenuating remodeling. The discussion on positive inotropic drugs focuses on cardiac glycosides like digoxin, which increases contractility by inhibiting the sodium-potassium ATPase pump, subsequently elevating intracellular calcium levels via the sodium-calcium exchanger; the text also notes digoxin's vagomimetic effects which slow heart rate and its narrow therapeutic index necessitating careful monitoring for toxicity such as visual disturbances and arrhythmias. Other inotropes discussed include the beta-adrenergic agonist dobutamine and the phosphodiesterase inhibitor milrinone, both utilized primarily for acute hemodynamic support. The chapter emphasizes the pivotal role of vasodilators and neurohormonal antagonists in modern therapy, specifically Angiotensin-Converting Enzyme inhibitors and Angiotensin Receptor Blockers, which reduce afterload and preload while mitigating myocardial fibrosis. Advanced therapies such as the neprilysin inhibitor sacubitril, combined with valsartan, are highlighted for their ability to augment beneficial natriuretic peptides. Furthermore, the text explains the paradigm shift regarding beta-blockers like carvedilol and metoprolol, which are now standard care to block sympathetic toxicity and apoptosis despite their negative inotropic properties. Additional agents covered include aldosterone antagonists like spironolactone and eplerenone for their antifibrotic survival benefits, loop diuretics like furosemide for managing pulmonary and peripheral edema, and the combination of hydralazine and isosorbide dinitrate for specific patient populations. The chapter concludes by outlining management strategies aimed at relieving dyspnea, reducing hospitalization, and improving mortality through a stepwise pharmacologic approach.