Harvard Heart Letter

Understanding silent heart attacks

Ask the doctor

Q. I understand that some people experience a heart attack without realizing they're having one. How are these heart attacks even discovered?

A. It's true that about half of all heart attacks are what are known as silent heart attacks, meaning they are not associated with any symptoms. In fact, the person may have experienced symptoms, such as chest discomfort and dizziness. But the symptoms may be been mild and short-lived and therefore unnoticed or ignored.

Silent heart attacks are usually discovered on an electrocardiogram (ECG), which is a recording of the heart's elec-trical activity. Damage to the heart's muscle caused by a heart attack shows up as a distinct signature on an ECG.

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