SPECIFIC HEART-MUSCLE DISEASE

Molecular techniques and ultrastructural analysis are beginning to pro vide insight into the etiologies of some specific heart muscle disorde rs. Studies using gene probes have suggested a role, in patients infec ted with HIV, for humoral- or cellular-mediated cardiac injury trigger ed by latent cytomegalovirus or other viral infections in the developm ent of AIDS-associated cardiomyopathy. In other such patients, structu ral and functional abnormalities of cardiac mitochondria, induced by a ntiretroviral agents, may play an important role. However, the likely multifactorial causes of this cardiomyopathy must be kept in mind. Sub stance abuse can impair ventricular function, as can antimicrobial age nts, such as pentamidine and ganciclovir, used to treat opportunistic infections in patients with acquired immunodeficiency syndrome. Advanc es in gene technology, especially the polymerase chain reaction, have allowed detailed analysis of mitochondrial DNA mutations. These mutati ons appear to be associated with the development of a wide range of ca rdiac disease, including specific heart muscle disease, such as that s een in Kearns-Sayre syndrome. An increasing variety of mitochondrial m yopathies with prominent cardiomyopathic features are being reported. Tissue characterization by ultrasonography appears to be a promising t echnique in the early detection of diabetic cardiomyopathy, before cli nical symptoms or frank abnormalities of systolic or diastolic functio n occur. In myotonic dystrophy, the patchy myocardial involvement, alt hough not affecting contractile function, may serve as a substrate for malignant ventricular arrhythmias. The use of cardioverter-defibrilla tor devices as primary therapy for patients with sarcoidosis and ventr icular tachycardia has been proposed.