What is acleistocardia?

Acleistocardia is a rare congenital heart condition in which part of the heart that separates the main pumping chambers (the ventricular septum) fails to fully develop, leaving a hole between the heart's lower chambers. A ventricular septal defect (VSD) can cause oxygen-rich and oxygen-poor blood to mix in the heart, increasing the workload on the heart while reducing the amount of oxygen that is supplied to the body.