restrictive cardiomyopathy

Imagine trying to fill a stiff leather bag versus a soft balloon: the leather resists expanding, so you can only force in a little water at high pressure. In restrictive cardiomyopathy the ventricular walls become abnormally stiff and cannot relax and stretch to take in blood, even though their squeezing strength is often near-normal. The problem is filling (diastole), not emptying.

Because the chambers fill poorly, pressure builds up behind them. Blood backs into the lungs and into the veins of the body, causing breathlessness, a swollen liver, abdominal fluid, and leg swelling — the picture of heart failure with relatively preserved pumping. The atria often enlarge as they strain against the stiff ventricles.

It is the least common of the main cardiomyopathy types. Causes include infiltration of the muscle by abnormal substances (such as amyloid protein or iron), scarring of the inner lining, and inherited disease; sometimes no cause is found. A key diagnostic challenge is distinguishing it from constrictive pericarditis, where a stiff sac around the heart — not the muscle — limits filling, because the two look similar but are treated very differently.