Restrictive Cardiomyopathy

Restrictive cardiomyopathy (RCM) is a myocardial disorder in which one or both ventricles cannot fill normally during diastole. The classic phenotype has normal or reduced diastolic and systolic chamber volumes, non-hypertrophied ventricular walls, and no coronary, hypertensive, valvular or congenital disease sufficient to explain the restriction. The defining problem is stiffness, not simply a low ejection fraction. A small increase in ventricular volume produces a disproportionate rise in filling pressure. Those pressures back up into the atria and venous circulation, while the amount of blood ejected with each beat remains relatively fixed. The result is a patient who may be markedly congested despite a preserved ejection fraction. This physiology makes the patient preload-dependent. Some filling is necessary to maintain output, but adding fluid does not reliably improve stroke volume because the stiff ventricle cannot accommodate it. Excess fluid instead raises atrial and venous pressures. The safe response to hypotension is therefore not an automatic fluid bolus; first assess rhythm, congestion, volume status and perfusion, then obtain urgent clinical direction. Biatrial enlargement is characteristic because both atria chronically eject against high...