Restrictive Cardiomyopathy

Overview
  • Restrictive Cardiomyopathy is the result of excessive rigidity of the ventricular walls, resulting in their poor diastolic relaxation. In contrast to hypertrophic cardiomyopathy, this functional change is not associated with ventricular hypertrophy or enhancement of ventricular contractility. Rather, most cases of restrictive cardiomyopathy are associated with deposition of substances within the myocardium which interfere with its normal flexibility and thus compliance.
Etiologies
  • Overview
    • A large variety of disease processes can result in restrictive cardiomyopathy. In general, these processes lead to deposition of substances within the myocardium that interfere its compliance and thus capacity to fill appropriately during diastole. The deposited substance may be collagen and the result of a fibrotic process within the myocardium or an abnormal substance produced outside of the heart which infiltrates into the myocardium. In general, the histomorphology of restrictive cardiomyopathy will vary given the specific etiology.
  • Specific Etiologies
    • Amyloidosis: Deposition of amyloid is the most common cause of restrictive cardiomyopathy. Any of the many subsclasses of amyloid can be responsible and all can be detected by characteristic apple-green birefringence under polarized light
    • Hemochromatosis: Results in deposition of Iron within the myocardium which induces significant myocardial fibrosis
    • Sarcoidosis: Myocardium displays infiltration with granulomas characteristic of this systemic disease
    • Radiation Injury: Can result in significant myocardial fibrosis
    • Loeffler Syndrome: Infiltration of heart with eosinophils and their degranulation results in extensive myocardial fibrosis
Clinical Consequences
  • Restrictive Cardiomyopathy ultimately results in poor ventricular compliance during diastole. Consequently, increased left atrial pressures and right atrial pressures are required to maintain sufficient cardiac output. Retrograde transmission of left atrial pressure into the pulmonary circulation gives rise to signs and symptoms akin to left heart failure such as dyspnea. Retrograde transmission of right atrial pressure into systemic veins gives rise to signs and symptoms of right heart failure such as peripheral edema and ascites. As restriction progresses, cardiac output becomes progressively more difficult to maintain and eventually begins to decline resulting in fatigue.