Silent Heart Attacks: Myocardial Infarctions Without Apparent Symptoms

A heart attack, or myocardial infarction (MI), is permanent damage to the heart muscle.

More than a million Americans have heart attacks each year.

Why Are Some Heart Attacks ‘Silent?’

By Richard N. Fogoros, MD

A silent heart attack is a heart attack that happens without causing noticeable symptoms—or at least, without causing symptoms so severe that the victim cannot ignore them.

Most of us tend to think about a myocardial infarction (heart attack) as a pretty dramatic event—and most of the time, it is. A heart attack is the most severe form of acute coronary syndrome (ACS), in which a coronary artery suddenly becomes blocked with a blood clot, which is usually caused by a sudden rupture of a plaque.

With a heart attack, the blockage is severe enough to cause a portion of the heart muscle to die, and to become converted to scar tissue.

Most people who are having a heart attack know right away that something is very wrong. Typically, they experience severe chest pain or some other form of extremely oppressive chest discomfort. And while the pain or discomfort may be “atypical” (for instance, it may affect the neck, shoulders or back instead of the chest itself), it is usually quite difficult to ignore. Additional symptoms are often present, which may include breaking out into a cold sweat, shortness of breath, or a feeling of impending doom. In short, a heart attack is usually more than merely “noticeable”—it is often as subtle as being hit in the face by a two-by-four.

So it may be surprising to hear that, for a substantial minority of people who have heart attacks, the heart attack is “silent.” That is, the heart attack occurs—acoronary artery is blocked by a blood clot and some of the heart muscle dies—without the victim being aware that anything in particular is happening.

There are several reasons why some people may have heart attacks without apparent symptoms. These include:

  • Some people simply have high pain thresholds, or a very high tolerance for pain, and simply do not “notice” symptoms that would be difficult for the rest of us to ignore.
  • Some medical conditions—in particular, diabetes—affect the nerves that carry pain impulses, so the symptoms of angina or a heart attack are blunted.
  • In some people, cardiac ischemia (a lack of blood flow to the heart muscle) simply does not produce chest pain, or other “typical” symptoms of angina. Instead, they may experience shortness of breath, or transient weakness, or other non-specific symptoms that most people would not immediately relate to their heart. “Atypical” symptoms with cardiac ischemia are especially likely in women.
  • Some people—especially when symptoms are relatively non-dramatic—are simply very good at ignoring the signs and symptoms of a heart attack, and are able to brush them off as being due to a cold, or “something I ate.”

When you add all these reasons up, it appears that about one out of five heart attacks turns out to be silent.

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