46% of 105 first-degree relatives had asymmetric septal hypertrophy, demonstrating that the disorder is transmitted as an autosomal dominant trait with a high degree of penetrance.

Idiopathic hypertrophic subaortic stenosis (hypertrophic cardiomyopathy) is transmitted as an autosomal dominant trait with high penetrance, and echocardiography is essential for family screening as clinical and ECG findings are often absent.