Silent Myocardial Infarction

A silent myocardial infarction, also called a silent or unrecognized heart attack, is damage to the heart muscle from a lack of blood flow that happens without the person noticing. There may be no symptoms at all, or the symptoms are so mild and atypical that they are mistaken for a cold or chill, an upset stomach, muscle aches, or ordinary tiredness. The condition is usually discovered weeks to years later, for example when a routine ECG shows Q waves that indicate scar tissue, or when echocardiography or cardiac MRI shows part of the heart wall that does not move normally.

How Common It Is and Why It Is Missed

Silent heart attacks are not rare. In the ARIC study in the United States, almost half of the myocardial infarctions found during follow-up were silent. A cardiac MRI study of older adults in Iceland also found more unrecognized infarctions than recognized ones. These infarctions are more easily missed in people with diabetes, because nerve damage can dull the sensation of pain, as well as in older adults and women, who more often have atypical symptoms.

How It Differs from Silent Ischemia

An infarction is different from ischemia. In ischemia, the heart muscle temporarily does not get enough blood but has not yet died, covered on the Silent Myocardial Ischemia page. In an infarction, part of the muscle has died and been replaced by scar tissue. Both are signs of coronary artery disease that need to be evaluated.

Why It Still Needs Treatment

Even though it happens without symptoms, this type of infarction carries risks similar to those of a recognized heart attack. A 2020 systematic review showed that people with an unrecognized infarction have a higher risk of death and further heart events than people without an infarction. The ARIC study also found a higher risk of heart failure. The first step is to confirm the finding, assess the heart's pumping strength, and check whether any part of the muscle is still not getting enough blood. Once identified, the condition can be managed like chronic coronary artery disease: heart-protective medications, risk factor control, and, if needed, a procedure to open the arteries. An overview of heart attacks is covered on the Myocardial Infarction / Heart Attack page.

A silent infarction is usually found during tests done for another reason, such as a routine health checkup, a diabetes follow-up, or preparation for surgery. Your doctor will ask about any vague symptoms you may have had, assess your risk factors, and check for signs of heart failure. An ECG may show pathological Q waves, which are traces of scar tissue in the heart wall, but an ECG alone is sometimes misleading.

For this reason, ECG findings are usually confirmed with echocardiography to look for wall segments that do not move normally and to assess pumping strength. Cardiac MRI with a contrast agent can show scar tissue in detail. Once an old infarction is confirmed, the doctor checks whether any heart muscle is still not getting enough blood, for example with stress echocardiography, myocardial perfusion imaging, or CT coronary angiography. Coronary angiography is performed if the results show severe narrowing or symptoms continue.

Make an appointment with a cardiologist if your ECG, echocardiography, or MRI results mention signs of an old infarction, Q waves, or abnormal heart wall motion, even if you feel healthy. If chest pain or pressure lasts more than 5 minutes, go to the nearest emergency room right away. A heart evaluation is also recommended if:

• You have diabetes or hypertension and have never had your heart checked.
• You have had unusual vague symptoms, such as a severe chill or extreme tiredness for several days.
• You get more short of breath during activities that used to feel easy.
• Your legs are swollen or you are short of breath when lying down.