What causes heart failure and how to look it up?

Causes of Heart Failure and How to Look It Up

Heart failure is caused primarily by coronary artery disease, hypertension, and dilated cardiomyopathy, with valvular heart disease also being a common cause. 1

Definition and Pathophysiology

Heart failure is a complex clinical syndrome that results from any structural or functional cardiac disorder that impairs the ability of the ventricle to fill with or eject blood. The cardinal manifestations include:

• Dyspnea and fatigue, which limit exercise tolerance 1
• Fluid retention, leading to pulmonary congestion and peripheral edema 1
• Progressive cardiac remodeling, where the chamber dilates, hypertrophies, and becomes more spherical 1

Common Causes of Heart Failure

Primary Causes:

• Coronary artery disease - Most common cause, responsible for approximately two-thirds of systolic heart failure cases 1
• Hypertension - Long-standing high blood pressure leads to left ventricular hypertrophy and dysfunction 1
• Dilated cardiomyopathy - Up to 30% of cases may have a genetic cause 1
• Valvular heart disease - Particularly mitral and aortic valve disorders 1

Other Significant Causes:

• Myocarditis - Inflammation of the heart muscle 2
• Cardiotoxic drugs - Including certain chemotherapeutic agents 2
• Alcohol abuse - Can lead to alcoholic cardiomyopathy 1, 2
• Thyroid disorders - Both hyperthyroidism and hypothyroidism 1, 3
• High-output states - Including severe anemia, arteriovenous fistulae, and hyperthyroidism 3
• Diabetes mellitus - Through microvascular disease and metabolic effects 1, 4
• Congenital heart disease - Various structural abnormalities 1
• Infiltrative diseases - Such as amyloidosis, sarcoidosis, hemochromatosis 2

How to Look Up Heart Failure

Initial Evaluation:

1. Clinical Assessment:

   • Assess for dyspnea, fatigue, exercise intolerance, and fluid retention 1
   • Look for displaced cardiac apex, third heart sound (S3), pulmonary rales, and peripheral edema 5
   • Determine NYHA functional class (I-IV) based on symptom severity 1

2. Basic Diagnostic Tests:

   • Chest radiography - Look for cardiomegaly, pulmonary congestion, interstitial edema 5, 4
   • Electrocardiogram - May show evidence of prior MI, LV hypertrophy, conduction abnormalities 1, 5
   • Laboratory assessment - Complete blood count, electrolytes, renal function, liver function, glucose, lipid panel, thyroid function 1, 4

3. Confirmatory Testing:

   • Echocardiography - Gold standard to confirm diagnosis, assess ejection fraction, evaluate structural abnormalities 1, 5
   • B-type natriuretic peptide (BNP) - Elevated in heart failure; useful for ruling out heart failure when normal 5

Advanced Evaluation:

• Determining Etiology:

  • Coronary angiography - To evaluate for coronary artery disease 5, 4
  • Cardiac MRI - For tissue characterization, viability assessment, and detection of infiltrative diseases 1
  • Specialized testing - May include genetic testing for familial cardiomyopathies, endomyocardial biopsy for suspected myocarditis 2

• Prognostic Assessment:

  • Cardiopulmonary exercise testing - To evaluate functional capacity and prognosis 1
  • Assessment of ventricular remodeling - Serial echocardiography to track disease progression 1

Classification Systems

1. NYHA Functional Classification - Based on symptom severity:

   • Class I: No limitation of physical activity
   • Class II: Slight limitation of physical activity
   • Class III: Marked limitation of physical activity
   • Class IV: Unable to carry out any physical activity without discomfort 1

2. ACC/AHA Staging System - Based on disease progression:

   • Stage A: At high risk but without structural heart disease
   • Stage B: Structural heart disease but without symptoms
   • Stage C: Structural heart disease with previous or current symptoms
   • Stage D: Refractory heart failure requiring specialized interventions 1

Common Pitfalls and Caveats

• Heart failure is not equivalent to cardiomyopathy or LV dysfunction; these terms describe possible structural or functional reasons for heart failure 1
• Patients with preserved ejection fraction (HFpEF) may have severe symptoms despite normal systolic function 1
• Heart failure is a progressive disorder; early identification and treatment of risk factors is crucial 1
• Medications like NSAIDs, certain calcium channel blockers, and some antiarrhythmics can worsen heart failure and should be used with caution 1
• Beta-blockers, while beneficial in chronic heart failure, can precipitate acute decompensation if initiated during unstable heart failure 6