Sudden unexpected infantile death due to undiagnosed ventricular septal defect-associated heart failure with single coronary artery

Ventricular septal defect (VSD) generally has a good prognosis unless complicated by heart failure (HF). We report a case of sudden infant death because of clinically undiagnosed VSD in a seemingly healthy 16-day-old boy. Although a cardiac murmur was auscultated at birth, detailed clinical examination was not performed. Medicolegal autopsy revealed a perimembranous large VSD with a single coronary artery. The infant was diagnosed to have had HF based on the increased weight of the heart and extremely high serum brain natriuretic peptide levels. Histological examination revealed the degeneration of cardiomyocytes. The large VSD was thought to be the major cause of HF, although single coronary artery-associated cardiomyopathy might have also partially contributed to it. The decline in the physiological neonatal pulmonary resistance, which occurs over the first 1 or 2 weeks following birth, led to the acute progression of HF, resulting in circulatory collapse and sudden death. Detailed clinical examination should be performed for neonates with cardiac murmur to prevent avoidable death.