Heart Failure Definition
Heart failure is a clinical syndrome characterized by symptoms (breathlessness, fatigue, ankle swelling) AND objective evidence of structural and/or functional cardiac abnormality, corroborated by elevated natriuretic peptide levels and/or objective evidence of pulmonary or systemic congestion. 1, 2, 3
Core Diagnostic Criteria
The diagnosis requires all three components to be fulfilled: 4, 1
- Symptoms of heart failure (at rest or during exercise): dyspnea, fatigue, ankle swelling 4, 1
- Objective evidence of cardiac dysfunction (systolic and/or diastolic) at rest, preferably by echocardiography 4, 1
- Elevated natriuretic peptides (BNP or NT-proBNP) and/or objective evidence of congestion 2, 3
A clinical response to treatment alone is insufficient for diagnosis, though patients should demonstrate improvement with appropriate therapy. 4, 1
Pathophysiological Basis
Heart failure results from any structural or functional cardiac disorder that impairs the ventricle's ability to fill with or eject blood. 1, 5 The syndrome can arise from disorders of the pericardium, myocardium, endocardium, heart valves, great vessels, or abnormalities of heart rhythm and conduction. 1
The underlying cardiac cause must always be identified - heart failure should never be the sole diagnosis. 1 Common etiologies include: 1, 6
- Coronary artery disease
- Hypertension
- Dilated cardiomyopathy (30% have genetic causes)
- Valvular heart disease
- Myocarditis
Classification by Ejection Fraction
Heart failure is classified based on left ventricular ejection fraction (LVEF): 1, 2, 3
- HFrEF (Heart Failure with Reduced EF): LVEF ≤40% 2, 3
- HFmrEF (Heart Failure with Mildly Reduced EF): LVEF 41-49% 2, 3
- HFpEF (Heart Failure with Preserved EF): LVEF ≥50% 2, 3
- HFimpEF (Heart Failure with Improved EF): Baseline LVEF ≤40%, ≥10-point increase, second measurement >40% 2, 3
Both systolic and diastolic dysfunction often coexist regardless of ejection fraction category. 1 Diastolic heart failure is more common in elderly patients and women, frequently associated with systolic hypertension and myocardial hypertrophy with fibrosis. 1
Clinical Presentation
Cardinal manifestations include: 1, 7
- Dyspnea (especially with exertion, paroxysmal nocturnal dyspnea) 1, 7
- Fatigue from low cardiac output, peripheral hypoperfusion, and skeletal muscle deconditioning 1, 7
- Fluid retention leading to pulmonary congestion and peripheral edema 1, 7
Physical examination signs: 1, 7
- Elevated jugular venous pressure 1, 7
- Pulmonary rales/crackles indicating pulmonary congestion 1, 7
- Peripheral edema, particularly ankle swelling 1, 7
- Hepatomegaly from systemic venous congestion 4
- Tachycardia as compensatory mechanism 7
Staging System
Heart failure stages represent disease progression: 4, 2, 3
- Stage A (At Risk): High risk but no structural heart disease or symptoms (hypertension, diabetes, atherosclerotic disease, obesity, family history of cardiomyopathy) 4, 2, 3
- Stage B (Pre-HF): Structural heart disease or elevated natriuretic peptides but no symptoms (LV remodeling, asymptomatic valvular disease) 4, 2, 3
- Stage C (Symptomatic HF): Structural heart disease with current or prior symptoms 4, 2, 3
- Stage D (Advanced HF): Refractory symptoms requiring specialized interventions, recurrent hospitalizations despite maximal therapy 4, 2, 3
Critical Diagnostic Considerations
The severity of symptoms correlates poorly with the degree of cardiac dysfunction. 4, 1 Patients with very low ejection fraction may be asymptomatic, while those with preserved LVEF may have severe disability. 4 This discordance may be explained by alterations in ventricular distensibility, valvular regurgitation, pericardial restraint, cardiac rhythm abnormalities, and right ventricular function. 4
A normal electrocardiogram makes heart failure, especially due to LV systolic dysfunction, unlikely. 4, 1 A low-normal BNP or NT-proBNP concentration in an untreated patient makes heart failure unlikely as the cause of symptoms. 4, 1
Progressive Nature
Heart failure is characteristically a progressive disorder even without new identifiable cardiac insults. 4 The principal manifestation is cardiac remodeling - the LV chamber dilates and/or hypertrophies and becomes more spherical, increasing hemodynamic stress and potentially worsening mitral regurgitation. 4, 7
Important Terminology
The term "heart failure" is preferred over "congestive heart failure" because not all patients have volume overload at initial or subsequent evaluations. 1 Acute heart failure refers to rapid onset or worsening requiring urgent treatment, while chronic heart failure is the persistent state punctuated by acute exacerbations. 1, 8