THE CONTEXT
Clinical assessment establishes whether an abnormal sound is cardiac, whether it is pathological and what causes it.
Establishing the sound's origin
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Additional heart sounds and murmurs have a consistent relationship to the cardiac cycle; extracardiac sounds such as a pleural rub or venous hum do not.
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Pericardial friction produces a characteristic scratching pericardial rub.
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A pericardial rub may have components corresponding to atrial and ventricular systole and may vary with posture and respiration.
Physiological and pathological sounds
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Pathological sounds and murmurs result from turbulent blood flow or rapid ventricular filling due to abnormal loading conditions.
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A third heart sound is common in young people and pregnancy but can also occur in heart failure.
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A systolic murmur from turbulence across the right ventricular outflow tract may occur in hyperdynamic states such as anaemia or pregnancy.
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The same outflow murmur may also result from pulmonary stenosis or an intracardiac shunt causing right ventricular volume overload, such as an atrial septal defect.
Features suggesting pathology
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Benign murmurs do not occur in diastole.
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Systolic murmurs that radiate or are associated with a thrill are almost always pathological.