How Diabetes Causes Heart Attacks

A recent study from Washington University in St Louis may explain why more than 75 percent of diabetics die of heart disease ( Journal for the American College of Cardiology , February 7, 2006). The heart muscle of diabetics uses a much higher percentage of fat for energy than that of non-diabetics, to markedly increase risk for heart attacks.

The energy source for heart muscle is mostly sugar and fat, and to a lesser degree, protein. Muscles need far more oxygen to process fat than to process sugar. The blood supply to heart muscle comes from large arteries on the outside of the heart. Diabetics have narrowed arteries because high blood sugar levels cause plaques to form and reduce the diameter of the coronary arteries. The increased need for blood flow from burning fat and the reduced blood flow from narrowed arteries put diabetics at very high risk for heart attacks, heart failure and sudden death. The increased use of oxygen increases blood levels of oxidants that further damage the inner linings of arteries.

Another study from Sweden shows that many people discover that they are diabetic only after they have had a heart attack. Researchers recorded blood sugar levels in men who had had heart attacks and then did sugar tolerance tests at discharge and three months later. They found that 35 percent had diabetic sugar tolerance tests at hospital discharge and 40 percent had impaired sugar tolerance tests three months later ( Lancet , Volume 359, 2002).

Therefore, 40 percent of people who have heart attacks are diabetic, even though they may not know it. Many of the diabetics had normal HBA1C blood tests, the standard test to measure diabetic control. Furthermore, the patients who were unknown diabetics had a much higher rate of sudden death from their heart attacks than those who were not diabetic. The authors recommend that all people with heart attacks be tested for diabetes.