EXERCISE THALLIUM TOMOGRAPHY PREDICTS FUTURE CLINICALLY MANIFEST CORONARY HEART-DISEASE IN A HIGH-RISK ASYMPTOMATIC POPULATION

Background Exercise testing, even when combined with radionuclide perf usion imaging, does not accurately predict future clinical coronary he art disease (CHD) in low-risk asymptomatic populations. We hypothesize d that these tests would perform better in a higher-risk population wi th a high preva lence of occult CHD. Siblings of persons with prematur e CHD represent such a group in whom it would be advantageous to ident ify affected individuals before the occurrence of clinically manifest CHD. Methods and Results Exercise thallium scintigraphy was performed in 264 asymptomatic individuals less than 60 years of age who had a si bling with documented CHD before age 60. Despite an average age of onl y 46 years at the time of screening, 19 of the 264 siblings developed clinical CHD (sudden death in 1, myocardial infarction in 10, coronary revascularization in 8) over a mean of 6.2 years (range, 1 to 9 years ) of follow-up. Abnormal thallium scans were observed in 29% of men an d 9% of women, while abnormal exercise ECGs occurred in 12% and 5%, re spectively. Of men greater than or equal to 45 years of age, 45% had a n abnormal exercise EGG, thallium scan, or both. In contrast, only 3% of women <45 years of age had an abnormal test result. Although abnorm al exercise ECGs and thallium scans were both predictive of future cli nical CHD, the thallium scan was associated with a higher relative ris k. After adjustment for age, sex, and exercise ECG results, the relati ve risk of developing clinical CHD was 4.7 for an abnormal scan. Sibli ngs with a concordant abnormal exercise ECG and thallium scan had a re lative risk of 14.5. These siblings were all men >45 years of age at t he time of screening and had a strikingly high incidence of clinical C HD (6 of 12, 50%). Conclusions Exercise thallium scintigraphy appears to be useful in the risk assessment of asymptomatic siblings of patien ts with premature CI-ID, particularly in male siblings who are 45 year s of age or older.