heart failure with reduced ejection fraction

HFrEF occurs when the heart's ability to contract and eject blood is impaired, leading to LVEF ≤40%. Pathophysiology involves loss of functional myocardium (e.g., from MI), leading to decreased stroke volume and cardiac output. This triggers compensatory neurohormonal activation: the renin-angiotensin-aldosterone system (RAAS) causes vasoconstriction and sodium/water retention, while sympathetic activation increases heart rate and contractility. Chronically, these compensatory mechanisms cause pathologic cardiac remodeling (eccentric hypertrophy, chamber dilation), worsening wall stress and further reducing EF—a maladaptive cycle.

Common etiologies: ischemic cardiomyopathy (most common), dilated cardiomyopathy, chronic uncontrolled hypertension, valvular disease (e.g., aortic regurgitation, mitral regurgitation), myocarditis, and toxin-induced (alcohol, doxorubicin).

Clinical presentation: dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, fatigue, peripheral edema, jugular venous distension, S3 gallop (due to rapid ventricular filling into a dilated, noncompliant ventricle), laterally displaced PMI.

Diagnosis: echocardiography is the gold standard, showing LVEF ≤40%. BNP/NT-proBNP elevated. CXR may show cardiomegaly, pulmonary congestion, Kerley B lines.

Management (mortality-reducing therapies): ACE inhibitors/ARBs or ARNI (sacubitril-valsartan), beta-blockers (carvedilol, metoprolol succinate, bisoprolol), mineralocorticoid receptor antagonists (spironolactone, eplerenone), SGLT2 inhibitors (dapagliflozin, empagliflozin). Diuretics (loop diuretics like furosemide) are used for symptomatic relief but do not improve mortality. Hydralazine/nitrates used especially in Black patients with persistent symptoms. Devices: ICD for primary prevention if EF ≤35% despite optimal medical therapy, cardiac resynchronization therapy (CRT) if EF ≤35% with LBBB and QRS >150ms.

Contrast with HFpEF (EF ≥50%), which involves diastolic dysfunction with preserved contractility but impaired relaxation/filling, often due to hypertension, diabetes, or infiltrative diseases (e.g., amyloidosis).

High-yield board points: S3 gallop is classic for HFrEF (volume overload), while S4 is associated with HFpEF (diastolic dysfunction/stiff ventricle). Know the four pillars of GDMT (guideline-directed medical therapy) for HFrEF: ACEi/ARB/ARNI, beta-blocker, MRA, SGLT2i—all shown to reduce mortality.