What would the effect interventricular septal defect have upon the blood flow?

An interventricular septal defect (VSD) allows blood to flow between the left and right ventricles of the heart, creating a left-to-right shunt. This abnormal flow increases the volume of blood in the right ventricle and pulmonary arteries, potentially leading to pulmonary overcirculation and increased pressure in the lungs. Over time, this can cause pulmonary hypertension and strain on the heart. If left untreated, it may lead to heart failure and other complications.