The combination of an exercise stress test and thallium scintigraphy imaging shows promise as an effective method to predict and prevent myocardial infarctions and other adverse cardiac events in the adult siblings of patients with heart disease, according to an article in the February 11th issue of Circulation. The pair of tests identified hidden heart disease among 1 in 5 seemingly healthy adults ages 30 to 59 years who had a brother or sister with known heart disease.

"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," said lead author Roger S. Blumenthal, M.D. "Aggressive testing clearly identifies individuals with hidden heart disease."

The American researchers screened more than 700 siblings of heart disease patients, collecting health histories, performing physical examinations, and identifying risk for heart disease on a standardized scale. Exercise stress tests included measurements of heart rate, blood pressure, and electrocardiographic activity. In addition to the stress testing, researchers used thallium scintigraphy. Radioactive dye was injected just before stopping exercise and images were collected immediately afterward.
Most of the siblings were middle-aged, male, and Caucasian with varying levels of education.

Of the 734 siblings screened, 153 (21 percent) had an abnormal exercise test, scintigram or both, of whom 105 were referred for angiography. Overall, 95 percent of the 105 siblings had evidence of heart disease, although only 39 percent had 1 or more blood vessels with at least 50 percent stenosis.

Of 30 siblings with both abnormal exercise tests and scintigrams, 70 percent had 1 coronary artery with at least 50 percent stenosis and 53 percent had an artery with at least 70 percent stenosis. The scintigrams accurately identified areas of the heart with low blood flow 71 percent of the time. The average narrowing among blood vessels feeding those regions of myocardium was about 43 percent.

The study found one gender difference: Most affected male siblings had a normal exercise test and an abnormal scintigram, whereas most female siblings had an abnormal exercise test and normal scintigram. Overall, siblings with abnormal results on both the exercise stress test and scintigraphy study were nearly 6 times as likely to have heart disease as those with only 1 abnormal test.

"Noninvasive testing represents a potentially fruitful approach for reducing the burden of death and disability from heart disease," concluded the authors.