Nearly 200,000 people are affected by an undiagnosed, or “silent,” heart attack in the United States each year, according to a new study by Duke University Medical Center Researchers.
A silent heart attack is both silent and potentially deadly, because no typical signs such as shortness of breath and severe chest pain are present.
Researchers estimate about 40 to 60 percent of all heart attacks may be of this “silent” type.
Silent heart attacks, also called non-Q-wave unrecognized myocardial infarctions (UMIs) often go undetected because the person doesn’t experience any pain and telltale irregularities are often undetectable on electrocardiograms (EKGs).
"No one has fully understood how often silent heart attacks occur and what they mean, in terms of prognosis," says Han Kim, MD, a cardiologist at Duke and the lead author of the study.
A heart attack is typically caused by a clot interfering with the flow of blood from a coronary artery to the heart. Well-known symptoms include severe chest pain, fainting, nausea and shortness of breath.
Risk factors are one in the same for both silent heart attacks and regular heart attacks, say experts, and include diabetes, stress, smoking and family history.
For the study, researchers used a new technique called DE-CMR (delayed enhancement cardiac magnetic resonance) on 185 patients who had never had a diagnosed heart attack but were suspected of having coronary artery disease.
A heart attack that occurred in the past may still leave a specific alteration on an ECG called a Q-wave, which signals the presence of damaged tissue. While silent heart attacks do not have associated Q-waves.
They followed up with patients after two years and found that 35 percent of patients had evidence of a heart attack and that silent heart attacks without Q-waves were three times more common than those that had Q-waves.
Those patients with non-Q-wave silent heart attacks also had 11 times greater risk of death from any cause and a 17-fold risk of death from heart problems compared with patients without heart damage.
Currently, there are no definitive treatment guidelines about how patients with UMIs should be treated, says Kim.
“If patients with UMIs are identified, they are typically treated similarly to those patients where heart disease has been previously documented. In future studies, researchers will likely examine how common unrecognized non-Q-wave heart attacks are in other patient groups and how UMIs should be treated.” #