A heart attack happens when blood flow to a part of your heart muscle is suddenly blocked. Sometimes heart attacks happen when the heart needs more oxygen than the blood vessels can provide. This might happen, for example, during hard exercise such as shoveling snow. The heart is a muscle like other muscles in your body. It needs oxygen, which it gets from the blood in blood vessels. The blood vessels that bring blood to the heart are called coronary arteries. A blood clot in one of these arteries can block the flow of blood to the heart muscle and cause the heart to stop working right. If the block lasts for many minutes, part of the heart can be injured.

The risk of a heart attack increases as you get older. Plaques (patches of cholesterol) may form in the arteries. This makes the arteries narrower inside. Blood clots may more easily form in a narrowed artery and block it. Both men and women have heart attacks.