Heart failure: definition and ventricular patterns
THE CONTEXT
Heart failure is a clinical syndrome involving inadequate cardiac output or adequate output maintained only through elevated ventricular filling pressure.
Clinical expression
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In mild to moderate heart failure, symptoms appear when metabolic demand rises during exercise or other stress. Severe heart failure may cause symptoms at rest.
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In a patient with heart disease, signs or symptoms of low cardiac output, pulmonary congestion or systemic venous congestion at rest or during exercise may establish the clinical diagnosis.
Left heart failure
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Left heart failure reduces left ventricular output and increases left atrial and pulmonary venous pressures.
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Sudden left heart failure, such as after an acute myocardial infarction, rapidly raises left atrial pressure and causes pulmonary oedema.
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A gradual rise in left atrial pressure, as in mitral stenosis, causes reflex pulmonary vasoconstriction that protects against pulmonary oedema.
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The resulting increase in pulmonary vascular resistance causes pulmonary hypertension, which can impair right ventricular function.
Right heart failure
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Right heart failure reduces right ventricular output and increases right atrial and systemic venous pressures.
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The most common causes listed are chronic lung disease, pulmonary embolism and pulmonary valvular stenosis.
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Cor pulmonale means right heart failure secondary to chronic lung disease.
Biventricular heart failure
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Both sides of the heart are affected in biventricular failure.
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A disease such as dilated cardiomyopathy or coronary heart disease may affect both ventricles directly.
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Alternatively, left heart disease may chronically elevate left atrial pressure, leading to pulmonary hypertension and subsequent right heart failure.