Ventricular Septal Defect

A ventricular septal defect is an opening in the wall that normally separates the two lower chambers of the heart. In a healthy heart, the left and right ventricles are fully divided, allowing oxygen-rich and oxygen-poor blood to flow through separate circuits. When an opening exists, blood can move between these chambers in a way that alters the usual flow. Many owners first become aware of the possibility when a heart murmur is heard during a routine examination, often in a young puppy or kitten. Some animals show no outward signs at all, while others may tire more easily during play, breathe more rapidly than expected, or grow at a slower pace than their littermates. The pattern often depends on the size of the opening and the direction and volume of blood moving through it. This page explores what an owner may observe, the underlying changes in heart structure and flow, the investigations that help characterise the defect, and the range of approaches that may be considered depending on the individual animal and the nature of the opening.