A heart attack happens when blood flow to part of the heart is blocked or severely restricted. If the blood flow is cut off for more than a few minutes, the muscle cells begin to die from lack of oxygen. Heart attack has a number of causes.
Coronary artery disease
The most common underlying cause of heart attack is atherosclerosis, a condition in which a fatty substance called plaque builds up on the inside walls of blood vessels. When this occurs in the coronary arteries, it's known as coronary artery disease (CAD).
Over time, the buildup of plaque can narrow or completely block the coronary arteries, restricting or preventing blood flow to the heart. Or the plaque can actually rupture, allowing a blood clot to form. If the clot becomes large enough, it can reduce or block the flow of blood to the heart.
Coronary microvascular disease
Coronary microvascular disease (MVD) affects the heart's smallest arteries rather than the large coronary arteries. Coronary MVD can be caused by plaque building up in the tiny arteries, spasms in the arteries themselves, or damage to the walls of the arteries.
Coronary MVD is thought to be more common in women than in men, and it's also believed to be one of the reasons heart disease is sometimes overlooked in women. That's because standard tests used to diagnose heart disease look for blockages in the coronary arteries, not plaque or spasms in the heart's microvasculature.
Coronary MVD is estimated to affect up to 3 million women with heart disease in the United States.
Coronary artery spasm
A less common cause of heart attack is a severe spasm (or contraction) of the muscles in the wall of one of the coronary arteries. The spasm can either restrict or block blood flow to the heart. Although the cause of such spasms isn't always clear, they can be triggered by emotional stress, exposure to cold, alcohol withdrawal, cigarette smoking, or cocaine use.