RIGHT-VENTRICULAR CARDIOMYOPATHY IN IDENTICAL AND NONIDENTICAL YOUNG TWINS

We describe the first sets of identical and nonidentical twins with ri ght ventricular cardiomyopathy (RVC). Pair A: A 12-year-old boy was re ferred because of palpitation and syncope. Clinical and instrument exa minations revealed an enlarged and depressed right ventricle (end-dias tolic volume = 110 Ml/M2; ejection fraction = 44%), spontaneous ventri cular tachycardia, and fatty-fibrous infiltrates in the biopsy specime ns. His asymptomatic, monozygotic twin showed localized involvement of the right ventricle with isolated, ventricular extrasystoles. Pair B. These 18-year-old nonidentical twin boys showed diffuse right ventric ular involvement (end-diastolic volume = 110 Ml/M2 and 114 Ml/M2; ejec tion fraction = 30% and 24%, respectively), induction of sustained and nonsustained ventricular tachycardia, respectively, and fibrosis on e ndomyocardial biopsy. One of the boys died suddenly at rest after docu mented ventricular fibrillation. These cases support the hypothesis of a genetic etiology with a minor role for genotype and point to the im portant influence of environmental factors in determining the clinical features of the disease.