Ventricular septal defect is an abnormal communication through the septum separating the right and left ventricles. It can be single or multiple, located in different areas of the septum. Most are asymptomatic at birth but may later cause failure to thrive and heart failure as pulmonary resistance decreases. Diagnosis is via echocardiogram. Small VSDs often close spontaneously but large defects require closure to prevent long term effects like pulmonary hypertension. Surgical patch closure is standard treatment for large unclosed VSDs.