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Heart Failure for ABIM

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Heart Failure for the American Internal Board of Medicine Exam
  • Definition: Heart failure (HF) is a clinical syndrome characterized by the heart's inability to pump sufficient blood to meet the body's metabolic demands. It can arise from structural or functional cardiac disorders that impair ventricular filling or ejection of blood.
  • Classification:
    • Heart Failure with Reduced Ejection Fraction (HFrEF): EF ≤40%, often due to systolic dysfunction.
    • Heart Failure with Preserved Ejection Fraction (HFpEF): EF ≥50%, often due to diastolic dysfunction.
    • Heart Failure with Mid-Range Ejection Fraction (HFmrEF): EF 41-49%, an intermediate group with features of both HFrEF and HFpEF.
Pathophysiology
left heart failure pathophysiology
  • Systolic Dysfunction (HFrEF):
    • Caused by impaired myocardial contractility, leading to reduced ejection fraction.
    • Common causes include ischemic heart disease, chronic hypertension, dilated cardiomyopathy, and valvular disease.
    • Leads to increased end-diastolic volume, which results in left ventricular (LV) dilation and wall stress, further reducing cardiac output.
  • Diastolic Dysfunction (HFpEF):
    • Characterized by impaired ventricular filling due to stiffened ventricles, leading to preserved ejection fraction with reduced stroke volume.
    • Common causes include chronic hypertension, aging, diabetes, and left ventricular hypertrophy.
    • Results in elevated filling pressures and pulmonary congestion despite preserved systolic function.
  • Compensatory Mechanisms:
    • Neurohormonal Activation:
    • Activation of the renin-angiotensin-aldosterone system (RAAS) increases sodium and water retention, leading to volume overload.
    • Sympathetic Nervous System activation increases heart rate and contractility but causes long-term deleterious effects, including increased myocardial oxygen demand and fibrosis.
    • Ventricular Remodeling: Myocardial hypertrophy and fibrosis occur as compensatory responses, worsening cardiac dysfunction over time.
Etiology of Heart Failure
  • Ischemic Heart Disease: The leading cause of HFrEF, often resulting from myocardial infarction and chronic ischemia.
  • Hypertension: A major contributor to both HFrEF and HFpEF; chronic pressure overload leads to LV hypertrophy and remodeling.
  • Cardiomyopathies: Both primary (genetic) and secondary causes, such as alcohol or chemotherapy-induced.
  • Valvular Heart Disease: Aortic stenosis and mitral regurgitation can lead to HF through pressure or volume overload, respectively.
  • Other Causes: Include arrhythmias (e.g., atrial fibrillation), myocarditis, and infiltrative diseases (e.g., amyloidosis).
Clinical Manifestations
  • Left-Sided Heart Failure:
    • Symptoms: Dyspnea, orthopnea, paroxysmal nocturnal dyspnea (PND), and fatigue.
    • Signs: Pulmonary rales, S3 or S4 heart sounds, and pulmonary congestion on imaging.
  • Right-Sided Heart Failure:
    • Symptoms: Peripheral edema, ascites, abdominal discomfort from hepatic congestion.
    • Signs: Jugular venous distention (JVD), hepatomegaly, hepatojugular reflux, and peripheral edema.
  • General Findings:
    • Exercise intolerance, cachexia in advanced cases, and signs of hypoperfusion, such as cool extremities and low blood pressure in severe HF.
Diagnostic Evaluation
  • Laboratory Tests:
    • Brain Natriuretic Peptide (BNP) or N-terminal pro-BNP (NT-proBNP): Elevated levels support a diagnosis of HF and are useful for assessing severity and prognosis.
    • Electrolytes and Renal Function: HF often leads to electrolyte imbalances and renal dysfunction due to neurohormonal activation and diuretic therapy.
  • Imaging:
    • Echocardiography: Key diagnostic tool to assess ejection fraction, ventricular size, wall thickness, and valvular abnormalities.
    • Chest X-ray: Shows cardiomegaly, pulmonary congestion, and pleural effusion in acute decompensated HF.
    • Cardiac MRI: Provides detailed information on myocardial structure and is useful in diagnosing myocarditis or infiltrative diseases.
  • Functional Assessment:
    • NYHA Functional Classification:
    • Class I: No symptoms with ordinary activity.
    • Class II: Symptoms with moderate exertion.
    • Class III: Symptoms with minimal exertion.
    • Class IV: Symptoms at rest.
Management of Heart Failure
Heart Failure with Reduced Ejection Fraction (HFrEF)
  • Pharmacologic Therapy:
    • ACE Inhibitors or ARBs: Reduce afterload, improve survival, and prevent remodeling.
    • Beta-Blockers: Reduce mortality by lowering heart rate and decreasing myocardial oxygen demand. Commonly used agents include carvedilol, metoprolol succinate, and bisoprolol.
    • Aldosterone Antagonists (e.g., spironolactone): Recommended for patients with NYHA class II-IV symptoms and EF ≤35% to reduce mortality.
    • SGLT2 Inhibitors (e.g., dapagliflozin): Recently shown to improve outcomes in HFrEF, even in non-diabetic patients.
    • Diuretics: Used for symptomatic relief of volume overload but do not reduce mortality. Loop diuretics are preferred (e.g., furosemide).
    • ARNI (angiotensin receptor-neprilysin inhibitor; e.g., sacubitril/valsartan): Recommended as an alternative to ACE inhibitors or ARBs in patients with symptomatic HFrEF to improve outcomes.
  • Device Therapy:
    • Implantable Cardioverter-Defibrillator (ICD): For primary prevention of sudden cardiac death in patients with EF ≤35% and NYHA class II-III symptoms despite optimal medical therapy.
    • Cardiac Resynchronization Therapy (CRT): For patients with EF ≤35%, NYHA class II-IV symptoms, and left bundle branch block (LBBB) with QRS ≥150 ms, improving symptoms and survival.
  • Advanced Therapy:
    • Mechanical Circulatory Support: Left ventricular assist device (LVAD) for patients with end-stage HF awaiting transplant or as destination therapy.
    • Heart Transplantation: For select patients with end-stage HF refractory to medical and device therapy.
Heart Failure with Preserved Ejection Fraction (HFpEF)
  • Management Principles:
    • HFpEF has fewer evidence-based therapies compared to HFrEF, focusing primarily on symptom management and comorbidity control.
    • Blood Pressure Control: Targeted to reduce ventricular stiffness and reduce the progression of HF.
    • Diuretics: For symptom relief in patients with volume overload.
    • Mineralocorticoid Receptor Antagonists: Spironolactone may improve outcomes in select patients with HFpEF.
    • SGLT2 Inhibitors: Emerging evidence supports use in HFpEF to improve quality of life and reduce hospitalization rates.
  • Management of Comorbidities:
    • Optimal control of hypertension, atrial fibrillation, diabetes, and obesity is crucial for HFpEF patients.
Acute Decompensated Heart Failure (ADHF)
  • Definition: ADHF is a rapid worsening of heart failure symptoms, often requiring hospitalization.
  • Clinical Presentation:
    • Acute dyspnea, orthopnea, pulmonary edema, and peripheral edema.
    • Hypoxia, respiratory distress, and hemodynamic instability in severe cases.
  • Management:
    • Oxygen Therapy: For hypoxia and respiratory distress.
    • Diuretics: IV loop diuretics are first-line for volume overload.
    • Vasodilators (e.g., nitroglycerin): For patients with severe hypertension and pulmonary edema.
    • Inotropes (e.g., dobutamine, milrinone): For patients with low cardiac output and end-organ hypoperfusion despite optimal volume status.
Key Points
  • Types of Heart Failure:
    • HFrEF: Characterized by systolic dysfunction and EF ≤40%.
    • HFpEF: Characterized by diastolic dysfunction and EF ≥50%.
    • HFmrEF: Intermediate group with EF 41-49%.
  • Pathophysiology:
    • Compensatory mechanisms, such as RAAS activation and sympathetic stimulation, initially support cardiac function but contribute to progression of HF.
  • Common Causes:
    • Ischemic heart disease, hypertension, valvular disease, and cardiomyopathies.
  • Diagnostic Evaluation:
    • BNP or NT-proBNP levels, echocardiography, and functional assessment (NYHA classification) are key in diagnosis and severity assessment.
  • Management of HFrEF:
    • Use of ACE inhibitors, beta-blockers, and aldosterone antagonists for survival benefit.
    • ICD and CRT are recommended in select patients to prevent sudden cardiac death.
  • Management of HFpEF:
    • Focus on controlling comorbidities and managing symptoms, with fewer evidence-based therapies available.
  • Acute Decompensated HF:
    • Managed with diuretics, oxygen, and vasodilators or inotropes depending on the clinical scenario.

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