Small Defects, Small Effects, Big Data, Big Anxiety: Our Evolving Understanding of Low-Risk Congenital Heart Disease.

It is rarely appropriate to close a ventricular septal defect (VSD) in an adult. This classic clinical pearl continues, either it is too small to cause problems or it is too big... and too late. Progress in diagnostic and interventional capabilities threaten the validity of such long-held, characteristically conservative medical wisdom. Just 2 or 3 decades ago, we were confident there was negligible if any long-term risk associated with a small unrepaired VSD; any remaining doubt about prophylactic intervention, perhaps due to the rare possibility of endocarditis, was quickly quashed by considering the only alternative to life with a small VSD: open-heart surgery. Noninvasive imaging has revolutionized diagnostic precision, whereas advances in surgical technique and the advent of catheter-based technology have dramatically altered the risk of intervention. Less well appreciated is how research using large datasets has influenced our perspective.