Experience from clinical genetics in hypertrophic cardiomyopathy: proposal for new diagnostic criteria in adult members of affected families.

The diagnosis of hypertrophic cardiomyopathy has relied on echocardiographic demonstration of unexplained left ventricular hypertrophy. The prevalence of hypertrophic cardiomyopathy defined in this way has been estimated to be 1:500 and experience indicates that these criteria are relatively specific when other causes of left ventricular hypertrophy are absent. In recent years, however, the systematic evaluation of pedigrees performed in the context of molecular genetic studies revealed that in some families with hypertrophic cardiomyopathy up to 20% of adults who carry a disease causing gene defect do not fulfil conventional echocardiographic criteria. None the less, most of these individuals show symptoms, electrocardiographic alterations, and/or minor echocardiographic abnormalities. Revised diagnostic criteria in members of families with hypertrophic cardiomyopathy are proposed, including major and minor criteria based on symptoms, and electrocardiographic and echocardiographic abnormalities. Given that the chance of inheriting the gene defect is 1:2, the likelihood that symptoms plus electrocardiographic or echocardiographic abnormalities are the expression of a disease causing gene is high.