Four-chamber dilatation with biventricular failure can come from very different mechanisms: Primary LV systolic dysfunction → secondary right heart involvement Restrictive cardiomyopathy (RCM) → bi-atrial enlargement, impaired filling, with eventual biventricular dysfunction Here’s how to clinically and echocardiographically sort them out: 1--History & Clinical Clues LV systolic failure (dilated cardiomyopathy, ischemic, valvular, etc.): Long history of CAD, hypertension, valvular disease, myoca