The condition, silent myocardial ischemia, occurs when plaque buildup or an obstruction causes heart arteries to narrow, restricting the flow of oxygen-rich blood to the heart. But while myocardial ischemia typically causes chest pain, silent myocardial ischemia, as its name implies, is usually pain-free.
"Typically, decreased blood flow to the heart causes the characteristic chest pain of angina – a tip-off that, without intervention, even more serious cardiac problems could result," says Antonio Q. Chan, M.D., lead author of the study. "But in our study, seven in 10 patients with myocardial ischemia never had chest pain, though many became fatigued easily or short of breath upon exertion.
"Any Asian American who complains of shortness of breath after climbing a flight or two of stairs, gets tired easily, or is over age 45 should be examined for the presence of ischemic heart disease," says Chan, an adjunct clinical associate professor of medicine (cardiology) at Stanford University Medical Center and chairman of the Chanwell Clinic in Cupertino, Calif. "This is especially important if the patient suffers from high blood pressure or diabetes, or has a family history of heart disease." He also notes that if there is a language, patients should seek a physician who speaks their the native language or has an interpreter.
Silent myocardial ischemia can only be diagnosed with specialized tests. The doctor may ask the patient to exercise on a treadmill, which increases the heart's work. An electrocardiogram, or EKG, that measures the electrical activity of the heart while the patient is exercising can reveal changes that occur with ischemia. A 24-hour continuous EKG can also detect the problem.
Or the doctor may order a stress echocardiogram to create ultrasound pictures of the heart. A drug called dobutamine is given through a vein and makes the heart work harder. In a patient with myocardial ischemia, the damaged part of the heart muscle moves slower than other areas of the heart. The ultrasound images reveal these damaged areas.
Chan and colleagues reviewed the medical records of 1,595 patients, of whom 662 were from a predominantly Caucasian-American practice in the Chicago area and 973 were from a predominantly Asian-American practice in the San Francisco Bay area.
All the patients had undergone a thorough exam in which doctors speaking their native language asked about possible symptoms of heart disease. This was followed by a treadmill EKG, a 24-hour EKG, or a dobutamine echocardiogram.
If myocardial ischemia was suspected, doctors confirmed the diagnosis using cardiac catheterization, a more sophisticated test that measures how much oxygen is in the blood and provides information about the pumping ability of the heart muscle. Among patients proven by cardiac catheterization to have myocardial ischemia, only 30 percent of Asian Americans suffered from chest pain (angina) compared with 83 percent of Caucasian Americans, Chan reports.
But there were other tip-offs that the Asian Americans might have a heart problem, he says. Asian Americans were more likely to become short of breath when exercising (63 percent vs. 36 percent of Caucasian Americans), suffer from fatigue (59 percent vs. 22 percent) and suffer from heart palpitations or rapid heart beats (65 percent vs. 24 percent).
"Asian Americans such as Chinese, Filipino and Vietnamese should be aware that the first sign of an impending heart attack is typically not the chest pain of angina, but more typically, symptoms of shortness of breath, easy fatigability or fast heart rate," he says.
Chan says that the mandated five-year waiting period before immigrants can quality for federal or state health insurance is a major deterrent to turning the tide in the fight against heart disease in Asian Americans.
"While they are waiting to qualify for health insurance, a lot of older immigrants have full-blown heart attacks, congestive heart failure and sudden death," he says. "Since a lot of the elder immigrants care for their grandchildren while their own children work, improving their health would improve the health and happiness of the entire family, which may include three generations living under one roof."
Co-authors are Clete Kushida, M.D., Ph.D.; Rosalinda A. Mandreza, M.D. and Zhuo Wen Chen.