Eisenmenger syndrome occurs when the increased pressure of the blood flow in the lung becomes so great that the direction of blood flow through the shunt reverses. Oxygen-poor (blue) blood from the right side of the heart flows into the left ventricle and is pumped to your body, making it so that you don't receive enough oxygen to all your organs and tissues. It is a life-threatening condition requiring careful medical monitoring. Medications can improve symptoms and prognosis. Eisenmenger syndrome signs and symptoms include: Bluish or grayish skin color (cyanosis), large, rounded fingernails or toenails (clubbing), easily tiring and shortness of breath with activity, shortness of breath while at rest, chest pain or tightness, skipped or racing heartbeats (palpitations), fainting (syncope), dizziness, numbness or tingling in the fingers or toes, headaches etc.