Combining an exercise stress test with an image of blood flow through the heart may be an effective method to predict and prevent heart attacks and other events among adult siblings of heart disease patients, a Johns Hopkins study has found.
The paired tests identified hidden heart disease among one in five seemingly healthy adults ages 30 to 59 who had a brother or sister with heart disease, according to results published in the Feb. 11 issue of Circulation, an American Heart Association journal.
"Although we already know the risk of siblings developing coronary artery disease is much higher than that of the general population, current guidelines do not target such families for aggressive preventive efforts," says lead author Roger S. Blumenthal, director of preventive cardiology at Johns Hopkins. "Aggressive testing clearly identifies individuals with hidden heart disease."
Researchers screened more than 700 siblings of heart disease patients, collecting their health histories, doing physical exams and identifying their risk for heart disease on a standardized scale. They also evaluated the siblings' performance during exercise stress tests, measuring heart rate, blood pressure and the heart's electrical function. Most of the siblings were middle-aged, male and white with varying levels of education.
For this study, doctors also used thallium scintigraphy, a two-dimensional imaging test that measures the amount of blood flow through the heart during exercise, showing whether the vessels expand normally to allow more blood to reach the heart. In this test, a radioactive dye is injected just before stopping exercise; afterward, the patient lies on a table while the doctor moves a small camera over the chest, recording signals sent out by the dye and translating them to computer images.
Of the 734 siblings screened, 153 (21 percent) had an abnormal exercise test, scintigram or both; 105 were referred for an angiogram (X-ray of the blood vessels). Overall, 95 percent of the 105 had evidence of heart disease, though only 39 percent had one or more blood vessels that were at least 50 percent narrowed by plaque (the definition of mild heart disease).
Of 30 siblings who had abnormal exercise tests and scintigrams, 70 percent had a blood vessel at least 50 percent narrowed by plaque, and 53 percent had a blood vessel at least 70 percent narrowed by plaque (the definition of significant heart disease). The scintigrams accurately identified areas of the heart with low blood flow 71 percent of the time. The average blockage among blood vessels feeding those areas was about 43 percent.
The study also found that:
Most male siblings had a normal exercise test and an abnormal scintigram, while most female siblings had an abnormal exercise test and normal scintigram.
Angiograms identified significant heart disease (one or more blood vessels at least 70 percent narrowed by plaque) in 23 percent of the 105 siblings studied.
Siblings with abnormal exercise tests and abnormal scintigrams were nearly six times as likely to have heart disease as those with only one abnormal test.
Blumenthal and colleagues note that medical therapy and lifestyle changes to lower cholesterol and blood pressure, even in people without high cholesterol or hypertension, result in a reduction in the number of heart disease-related events.
Noninvasive testing represents a potentially fruitful approach for reducing the burden of death and disability from heart disease, they conclude.
The study was supported by the Johns Hopkins General Clinical Research Center, the National Institute of Nursing Research and the National Heart, Lung and Blood Institute. Co-authors were Diane M. Becker, Lisa R. Yanek, Thomas R. Aversano, Taryn F. Moy, Brian G. Kral and Lewis C. Becker.