Heart Sounds

Key points

• S1 (mitral + tricuspid closure): soft if long PR or MR; loud in mitral stenosis.
• S2 (aortic + pulmonary closure): soft in aortic stenosis; inspiratory splitting is normal.
• S3 (diastolic filling): normal < 30 years (women up to 50); pathological in LVF/DCM · constrictive pericarditis ('pericardial knock') · MR.
• S4 (atrial contraction against stiff ventricle): aortic stenosis · HOCM · hypertension; palpable S4 → double apical impulse in HOCM.
• Auscultation sites: pulmonary L 2nd ICS upper sternal border · aortic R 2nd ICS · mitral L 5th ICS medial to MCL · tricuspid L 4th ICS lower sternal border.