Key Concepts
Introduction
Heart sounds are produced by the closure of cardiac valves during the cardiac cycle. S1 (lub) occurs when the mitral and tricuspid valves close at the beginning of systole, and S2 (dub) occurs when the aortic and pulmonic valves close at the beginning of diastole. S3 may indicate heart failure in adults due to rapid ventricular filling against a non-compliant ventricle. S4 represents atrial contraction against a stiff ventricle, often associated with ventricular hypertrophy. Murmurs result from turbulent blood flow across abnormal valves, septal defects, or increased flow states. Auscultation requires systematic listening at all valve areas using both the bell (low-pitched sounds) and diaphragm (high-pitched sounds). On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that...