Pharmacology  ·  Cardiovascular

Heart Failure: Pathophysiology and the Four Pillars

Ejection fraction classification, neurohormonal cascade, cardiac remodeling, and guideline-directed therapy framework

• Heart failure is classified by left ventricular ejection fraction because this single measurement predicts prognosis and determines which drug classes have proven survival benefit — reduced ejection fraction (≤40%) has the strongest evidence base; preserved ejection fraction (≥50%) accounts for roughly half of all cases and was until recently without a proven mortality-reducing drug.
• The neurohormonal cascade is the engine of disease progression: reduced cardiac output activates the renin-angiotensin-aldosterone system and the sympathetic nervous system, responses that are adaptive acutely but harmful chronically, driving fibrosis, hypertrophy, and progressive remodeling.
• Cardiac remodeling and neurohormonal activation reinforce each other in a self-amplifying cycle — guideline-directed medical therapy interrupts this cycle and can partially reverse the structural changes, which is why these drugs improve survival rather than only relieving symptoms.
• The natriuretic peptide system is the heart's counter-regulatory response to wall stress; neprilysin breaks down these protective peptides, and blocking neprilysin alongside renin-angiotensin-aldosterone system blockade (sacubitril/valsartan) amplifies their beneficial effects.
• The four pillars of guideline-directed medical therapy — RAAS blockade or neprilysin inhibition, beta-blockade, mineralocorticoid receptor antagonism, and SGLT2 inhibition — are started together rather than sequentially, as each independently reduces mortality.