Eisenmenger syndrome

Eisenmenger syndrome is most often a complication of having a hole between two chambers of the heart. The hole is called a ventricular septal defect. It causes more blood to flow to the lungs' arteries. Eventually the extra blood flow causes blood vessels to stiffen and narrow, increasing pressure in the lungs' arteries. The high pressure causes the walls of the right lower heart chamber, called the right ventricle, to get thick.