Heart failure
Also known as: congestive heart failure, CHF
Heart failure is a clinical syndrome in which the heart cannot pump enough blood to meet the body's metabolic demands, or can do so only at elevated filling pressures. It produces congestion behind the failing chamber and reduced perfusion ahead of it.
Heart failure is a syndrome rather than a single disease. The common feature is inadequate cardiac output relative to demand, arising either because the ventricle cannot contract forcefully enough (systolic dysfunction, or heart failure with reduced ejection fraction) or because a stiff ventricle cannot fill adequately during diastole (diastolic dysfunction, or heart failure with preserved ejection fraction). Ischemic heart disease, long-standing hypertension, valvular disease, and cardiomyopathies are the most common underlying causes.
Symptoms follow directly from which side of the heart is failing. Left-sided failure backs blood up into the pulmonary circulation, producing dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, pulmonary edema, and crackles on auscultation. Right-sided failure backs blood up into the systemic veins, producing jugular venous distension, peripheral edema, hepatomegaly, and ascites. The most common cause of right-sided failure is left-sided failure; isolated right-sided failure from pulmonary disease is called cor pulmonale.
Reduced cardiac output triggers compensatory responses that eventually worsen the disease. Baroreceptor-mediated sympathetic activation raises heart rate and contractility, while reduced renal perfusion activates the renin-angiotensin-aldosterone system, retaining sodium and water. These raise preload and afterload, increasing ventricular wall stress and driving pathologic remodeling — which is why blocking these pathways with ACE inhibitors, beta blockers, and aldosterone antagonists improves outcomes, while diuretics relieve congestive symptoms.
USMLE Step 1 tests the pathophysiology in depth: pressure-volume relationships, ejection fraction, Frank-Starling mechanics, neurohormonal compensation, and the drug classes that interrupt it. The CCMA covers cardiovascular disorders and blood pressure conditions from the medical assistant's perspective, and the NPTE-PTA addresses heart failure through cardiac exercise testing, activity tolerance, and cardiac rehabilitation programming.
Key takeaways
- Heart failure means the heart cannot meet the body's circulatory demands at normal filling pressures.
- Systolic dysfunction reflects impaired contraction (reduced ejection fraction); diastolic dysfunction reflects impaired filling (preserved ejection fraction).
- Left-sided failure causes pulmonary congestion; right-sided failure causes systemic venous congestion and peripheral edema.
- Left-sided failure is the most common cause of right-sided failure.
- Sympathetic and renin-angiotensin-aldosterone activation initially compensate but ultimately accelerate ventricular remodeling.