What congenital heart defect is most commonly associated with Eisenmenger syndrome?

The congenital heart defect most commonly associated with Eisenmenger syndrome is a large ventricular septal defect (VSD). Eisenmenger syndrome occurs when there is a left-to-right shunt due to a congenital heart defect that causes increased blood flow to the lungs. Over time, this increased pressure results in pulmonary vascular remodeling, leading to pulmonary hypertension. Due to the VSD's significant shunt and associated volume overload, it can lead to the development of Eisenmenger physiology, where the pulmonary artery pressures eventually exceed systemic pressures, resulting in a right-to-left shunt and cyanosis.

The connection between large VSDs and Eisenmenger syndrome is crucial. The volume overload caused by the shunt from the left ventricle to the right ventricle leads to increased pulmonary blood flow, which causes the pulmonary arteries to experience consistent high pressure. This chronic overload directly induces vascular changes that culminate in pulmonary hypertension, making large VSDs the most common defect leading to this condition.

While other congenital heart defects can lead to similar hemodynamic changes, they are typically not as directly linked to the development of Eisenmenger syndrome. For example, atrial septal defects may cause right heart volume overload but generally lead to less severe pulmonary hypertension