Rapid evolution from "normal" left ventricular outflow tract to fatal subaortic stenosis in infancy.

Serial clinical, echocardiographic, haemodynamic, and angiocardiographic data support the conclusion that over four months severe discrete subaortic stenosis evolved from a previously angiocardiographically normal left ventricular outflow tract in an infant who had a successful repair of thoracic aortic coarctation. This case supports those who suggest that a myocardial factor may play an important role in the change in form and function of some congenitally malformed hearts.