Invasive techniques that improve the blood supply to the heart also may be used. Another procedure is coronary artery bypass graft surgery. Before performing either of these procedures, a doctor must find the blocked part of the coronary arteries. This is done using coronary arteriography, which is done during a procedure called cardiac catheterization. Then the doctor injects a liquid dye visible in X-rays through the catheter.
Doctors can identify obstructions in the arteries by tracing the liquid's flow.
Some newer diagnostic procedures are available to evaluate how well the heart works. These tests may be done before or after a heart attack. In it a doctor inserts a catheter into an artery in an arm or leg and guides it to an obstructed coronary artery. Then a second catheter with a balloon tip is passed inside the first, and the balloon tip is inflated at the arterial blockage. This compresses the plaque, enlarging the inner diameter of the blood vessel so blood can flow more easily.