Eisenmenger syndrome

Eisenmenger syndrome is most often a complication of having a hole between two chambers of the heart. Here, a hole between the heart's main pumping chambers (ventricular septal defect) causes more blood to flow to the lungs' arteries. Eventually this causes these blood vessels to stiffen and narrow, increasing pressure in the lungs' arteries. The high pressure causes the walls of the right lower heart chamber (right ventricle) to thicken (hypertrophy).