心臓試験 III: 異常な心臓の音
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Q1: What causes heart murmurs and how are they classified?
Murmurs result from turbulent blood flow across heart valves, caused by stenosis (valve narrowing) or regurgitation (blood backflow). They are classified by intensity on the Levine scale (1-6), pitch, quality, configuration, location, and timing in the cardiac cycle. Systolic murmurs can be benign in younger people, while diastolic murmurs typically indicate pathology.
Q2: How do you distinguish aortic stenosis from aortic regurgitation by sound?
Aortic stenosis produces a harsh, systolic, crescendo-decrescendo murmur radiating to the carotid arteries. Aortic regurgitation sounds soft and blowing, occurring in early diastole with a decrescendo pattern. Both are left-sided murmurs, but their timing, quality, and radiation patterns differ significantly during auscultation and working mechanism of a stethoscope evaluation.
Q3: What are S3 and S4 gallops and what do they indicate?
S3 and S4 are abnormal heart sounds occurring when more than two sounds occur in a row. S3 is a low-pitched early diastolic sound caused by blood entering the ventricle, indicating advanced heart failure or normal in younger patients. S4 occurs in late diastole from atrial contraction against a stiff ventricle, associated with heart failure and left ventricular hypertrophy.
Q4: What is the difference between physiological and paradoxical S2 splitting?
Physiological S2 splitting occurs during inspiration when aortic and pulmonary valve closure separates normally. Paradoxical splitting happens during expiration due to prolonged left ventricular phase, seen in left bundle branch block or hypertrophic cardiomyopathy. Fixed splitting throughout the respiratory cycle indicates atrial septal defect.
Q5: How should you position a patient to detect mitral stenosis during cardiac examination?
Instruct the patient to lie on their left side and use the bell of the stethoscope pressed lightly on the chest. Auscultate the mitral area in this position to detect the low-frequency, rumbling, mid-diastolic murmur characteristic of mitral stenosis. This positioning enhances sound transmission and helps identify subtle abnormal sounds.
Q6: What maneuver accentuates the murmur of hypertrophic cardiomyopathy?
The Valsalva maneuver accentuates hypertrophic cardiomyopathy murmurs. Ask the patient to blow out with their mouth closed while auscultating between the apex and left lower sternal border using the diaphragm. If a systolic, crescendo-decrescendo murmur appears or intensifies, this confirms the diagnosis of this genetic disorder causing abnormal cardiomuscular wall thickening.
Q7: What is a pericardial friction rub and how does it differ from other abnormal sounds?
A pericardial friction rub is an abnormal sound caused by inflammation of the pericardium, where the inner and outer pericardial layers rub against each other. Unlike murmurs from valvular pathology or gallops from ventricular filling, friction rubs are heard best at the lower left sternal border with the patient leaning forward, indicating pericarditis rather than valvular disease.