Occasionally you will be present when a case is demonstrated in which the patient has a cardiomyopathy clinically, but on echo, MRI or whatever, the ventricles show normal size and reasonable contractility. The differential here has only two members, constrictive pericarditis and "restrictive" cardiomyopathy (RCM). You can tell the difference by looking at the excursion of the mitral ring. In constriction the ring moves briskly and most-times with a greater amplitude, and the apex is stationary. In RCM the reverse is the case, as you can see in the images above. The ring is stationary and the apex moves in and out. Enthusiasts of echo and MRI claim to have discovered this, but in fact we were using these features as seen on classic left ventriculography decades ago.