A study was recently conducted using new imaging technology. It found that “silent” heart attacks may not only be far more common than suspected, but also more deadly. Some studies estimate that these heart attacks, often painless, affect 200,000 people in the United States each year. Duke University’s Dr. Han Kim suspects the numbers may be far higher.
Unrecognized Myocardial Infarctions, the name given to these silent heart attacks, are not yet fully understood, in terms of both prognosis or how often they occur.
Doctors are usually able to tell whether a patient has had a recent heart attack by looking for changes in a number of places. They look for signature changes on a test of the heart’s electrical activity called an electrocardiogram. They also check for particular enzymes in the blood.
Doctors will also look for changes on an electrocardiogram called Q-waves. The only problem is that not all silent heart attacks will result in Q-waves. Patients who suffer from the silent heart attacks are then treated for heart disease alone.
But Dr. Kim and his colleagues used a new type of magnetic resonance imaging technology, called delayed enhancement cardiovascular resonance, which is especially adept at finding damaged heart tissue. The study was conducted on 185 patients with coronary artery disease, and no record of heart attacks. 35 percent of the patients had evidence of a prior heart attack. Not only that, but non-Q-wave heart attacks were three times more common than silent heart attacks with Q-waves.
After two years of follow-up, people who suffered a silent, non-Q-wave heart attack had 11 times the risk of death from any cause. Those same patients also had 17 times the risk of death due to heart problems. This is in comparison to patients without any heart damage.
The study will appear next week in the Public Library of Science journal PLoS Medicine