Restrictive cardiomyopathy (RCM) is a less common type of cardiomyopathy; only 3 to 5 percent of children diagnosed with cardiomyopathy have RCM. According to the Pediatric Cardiomyopathy Registry, RCM occurs at a rate of less than one per million children. While RCM can develop at any age, the average age of diagnosis is 5 to 6 years. Some studies suggest that RCM may be slightly more common in girls than boys.
With RCM, the heart has normal pumping function but difficulty relaxing properly. The heart walls become rigid and are unable to expand properly. As a result, the upper chambers of the heart (atria) become enlarged, while the lower chambers (ventricles) remain normal in size. Eventually, the heart chambers are unable to adequately fill with blood because of stiffness in the heart. With RCM there is an increased risk of sudden cardiac arrest and worsening heart failure.
Causes of Restrictive Cardiomyopathy
While RCM in adults typically occurs related to another disease, the causes in children are usually unknown (idiopathic). RCM is not typically inherited although there have been cases where multiple family members have a combination of hypertrophic and restrictive cardiomyopathies.
Some infiltrative disorders can lead to RCM. These include an abnormal protein buildup in the heart (amyloidosis), excess iron in the heart (hemochromatosis), lysosomal storage diseases (Fabry, Gaucher, Hurler disease) and sarcoidosis. Endomyocardial fibrosis is also a common cause in certain tropical areas.