CLINICAL PROGRESS The Natural History of Ventricular Septal

many problems remain unanswered concerning its natural course. What is the long-term outlook for the patient with the small or moderate-sized defect? What is the lifetime risk of infective endocarditis? What is the origin of the pulmonary hypertension in ventricular septal defect and its relation to pulmonary vascular changes over the years? What is the importance, incidence, or even existence of spontaneous closure of ventricular septal defect? It is unfortunate, academically and practically, that just as we have entered an era when information of this nature might be secured, the disease may all but vanish in the wake of modern surgical treatment. Indeed, with the surgical risk of repair falling below the 5-per cent level, we may ask ourselves,