Heart Failure: A High-Yield USMLE Review

Heart failure is a syndrome—not a single diagnosis—in which the heart cannot deliver adequate cardiac output and/or maintain normal filling pressures, producing congestion and hypoperfusion. It is classified by ejection fraction into HFrEF (LVEF ≤40%) and HFpEF (LVEF ≥50%), a distinction that fundamentally changes management. On the exam, you must confirm the syndrome, classify by EF, identify the cause, assess the hemodynamic profile, and treat according to evidence.

Presentation

• Dyspnea, orthopnea, and fatigue are the cardinal symptoms; associated respiratory distress, tachypnea, accessory muscle use, and inability to speak in full sentences signal severity.
• Signs of congestion: elevated JVP (right-sided congestion), crackles/pulmonary edema, pleural effusions, hepatomegaly, hepatojugular reflux, ascites, and bilateral pitting peripheral edema.
• Cardiac findings: S3 gallop (volume overload, classic for HFrEF), S4 gallop (stiff ventricle, HFpEF/hypertension), displaced PMI (LV dilation), and functional murmurs such as mitral regurgitation.
• Low-output/perfusion signs: tachycardia, narrow pulse pressure (low stroke volume), hypotension, cool extremities, and cachexia in advanced disease.
• Cheyne-Stokes respiration (periodic breathing) is a poor prognostic sign; hyponatremia is likewise a marker of poor prognosis.

Diagnosis

• Confirm the syndrome with symptoms (dyspnea, orthopnea, fatigue) plus signs of congestion/low output plus objective evidence such as elevated BNP and characteristic echo findings.
• Echocardiography classifies by EF (HFrEF ≤40% vs. HFpEF ≥50%) and reveals structural clues—chamber dilation, wall motion, valvular disease, and functional MR.
• Elevated BNP (released with ventricular stretch) supports the diagnosis and reflects hemodynamic stress.
• Identify the underlying cause: ischemic (coronary angiography), hypertensive, valvular, toxic (alcohol, anthracyclines, trastuzumab), genetic/familial, peripartum, tachycardia-mediated, or infiltrative; cardiac MRI can characterize the myocardium and endomyocardial biopsy is reserved for cases where a specific diagnosis changes management.
• Assess the hemodynamic profile (warm/cold, wet/dry) to guide acute management.

Management

• HFrEF—use the four pillars of guideline-directed medical therapy at target doses: ARNI (or ACE inhibitor/ARB), beta-blocker, mineralocorticoid receptor antagonist (MRA), and SGLT2 inhibitor. These block maladaptive neurohormonal activation and reduce mortality; asymptomatic low BP or HR is common in well-treated patients and is not a reason to reduce doses.
• HFpEF—diuretics for congestion, SGLT2 inhibitors, and treatment of underlying conditions.
• Acute decompensation—stabilize (ABCs, oxygen to keep SpO2 >90%, upright positioning, BiPAP/CPAP if severe distress), then treat by hemodynamic profile. For 'wet' patients, give IV loop diuretics first-line (furosemide, bumetanide, torsemide) at a dose at least equal to the oral daily dose; if inadequate, double the dose or add a thiazide for synergy. Add vasodilators (nitroglycerin for preload reduction; nitroprusside in hypertensive emergency) and consider inotropes for 'cold' profiles.
• Optimize GDMT at target doses before pursuing advanced therapies—ICD, CRT, or transplant evaluation.
• Advanced/end-stage options: LVAD as a bridge to transplant or destination therapy (complications include bleeding, infection, thrombosis, RV failure) and heart transplantation, the definitive treatment, limited by donor availability and requiring lifelong immunosuppression.
• Manage HF-related hyponatremia with fluid restriction (typically 1.5–2 L/day), diuresis, and optimization of cardiac output; avoid hypertonic saline in volume overload, and consider vasopressin antagonists (tolvaptan) in refractory cases.
• Avoid harmful interventions: NSAIDs (cause sodium retention and blunt diuretics), excess fluids, negative inotropes in cardiogenic shock, and calcium channel blockers (except amlodipine) in HFrEF.

High-yield

• S3 gallop = volume overload/HFrEF; S4 gallop = stiff ventricle/HFpEF or hypertension.
• The four pillars of HFrEF therapy—ARNI, beta-blocker, MRA, SGLT2 inhibitor—work by blocking maladaptive neurohormonal activation, and their survival benefit is achieved at target doses.
• ARNI (sacubitril) enhances natriuretic peptide activity by blocking their breakdown; BNP rises with ventricular stretch.
• Hyponatremia in HF is dilutional (ADH-driven) and a poor prognostic sign; Cheyne-Stokes respiration also portends poor prognosis.
• Hemodynamic profiling (warm/cold, wet/dry) drives acute therapy: warm-and-wet → diuresis and vasodilation; cold-and-wet → inotropes with careful diuresis.
• Elevated JVP reflects right-sided congestion and right atrial pressure; loss of atrial kick in atrial fibrillation is especially detrimental in HFpEF.
• Diuresis helps by shifting the congested patient back toward the optimal point on a flattened Frank-Starling curve.

Pitfalls

• Do not reduce GDMT doses for asymptomatic low BP or bradycardia—reserve dose reduction for symptomatic hypotension, symptomatic bradycardia, severe hyperkalemia, or acute kidney injury.
• Clear lung fields do not exclude heart failure: in chronic HF, pulmonary lymphatics adapt and crackles may be absent despite markedly elevated filling pressures—use the whole clinical picture.
• Don't forget to search for a precipitant—every decompensation has a trigger that must be identified and addressed.
• Avoid NSAIDs, excess fluids, negative inotropes in cardiogenic shock, and non-dihydropyridine calcium channel blockers in HFrEF.
• Don't treat HF hyponatremia as sodium depletion—patients have total body sodium excess (hence edema) with relatively more excess water; hypertonic saline is inappropriate.
• Failing to classify by EF leads to wrong therapy: HFrEF and HFpEF are managed fundamentally differently.