Cardiac Anatomy and Physiology
Chambers and valves
You must move fluently between structure, coronary supply, and phase of the cardiac cycle. The right atrium receives the SVC, IVC, and coronary sinus. The right ventricle is identified by the moderator band, coarse trabeculae, and the crista supraventricularis; its tricuspid valve inserts more apically than the mitral valve, and that normal offset is what separates Ebstein anomaly from artifact. The left atrium lies most posteriorly, which is why it sits in the far field from the apex and is the chamber indexed for volume (normal ≤34 mL/m²). The aortic valve is trileaflet, sits above the membranous septum, and shares fibrous continuity with the anterior mitral leaflet.
Coronary territories and the 17-segment model
Six basal, six mid, four apical segments plus an apical cap make up the AHA model. The LAD supplies anteroseptal, anterior, and apical segments; the RCA supplies inferior and basal-to-mid septal segments plus the RV free wall; the LCx supplies lateral and inferolateral walls. The anterolateral papillary muscle is LCx-supplied and the posteromedial is RCA-supplied, which explains posterior leaflet flail after inferior infarction.
Cardiac cycle
Diastole is isovolumic relaxation, rapid filling, diastasis, and atrial kick; systole is isovolumic contraction and ejection. Chamber sizes are taken at end-diastole, defined as the first frame after QRS onset or the largest dimension.
Traps and a rule of thumb
Trabeculations, false tendons, and the crista can mimic thrombus or mass. Never call a wall thick without measuring: >1.1 cm is hypertrophy, >1.5 cm with a speckled texture raises amyloid, and a septal-to-posterior ratio ≥1.3 suggests hypertrophic cardiomyopathy. Rule of thumb: a structure that does not move with the myocardium and sits in the near field of an apical view is artifact until proven otherwise.