What is the pathophysiology of Eisenmenger's syndrome?

Eisenmenger's syndrome is characterized by the progression of a congenital heart defect leading to a significant increase in blood flow to the lungs, which results in pulmonary hypertension. Initially, conditions like a ventricular septal defect or atrial septal defect allow for left-to-right shunting of blood. This abnormal flow increases the volume of blood flowing into the pulmonary circulation, causing the pulmonary arteries to become overloaded.

Over time, the sustained increase in pulmonary blood flow leads to vascular remodeling and progressive pulmonary artery hypertension. This elevated pressure in the pulmonary circulation eventually causes a reversal of the shunt from right to left, which is the hallmark of Eisenmenger's syndrome. The consequences of this reversal lead to cyanosis and other systemic manifestations due to deoxygenated blood being circulated to the body.

Understanding this mechanism is crucial, as it underscores the importance of early diagnosis and management of congenital heart defects before they progress to Eisenmenger's syndrome.