Noninvasive coronary risk stratification of elderly patients

The prognostic value of stress thallium-201 myocardial perfusion imaging has not been defined in an elderly (≥ 70 years) population. To this end, we studied 468 consecutive elderly patients undergoing either Bruce protocol exercise stress (n = 120) or intravenous dipyridamole stress (n = 348) with quantitative planar thallium-201 imaging. These patients were followed for at least 2 years after testing to determine their rates of cardiac events (cardiac death, myocardial infarction, coronary revascularization). There were no stress-related complications in either subgroup. A 10% cardiac event rate (6 deaths and 6 myocardial infarctions) were observed in the exercise subgroup. Survival without cardiac events was associated with greater exercise duration (5.6±2.4 vs 3.1±2.4 min; P < 0.001) and peak exercise heart rate (131±18 vs 120±19 bpm; P < 0.05). Multivariate analysis identified the combination of peak exercise ≤ Stage 1 and thallium-201 perfusion defects as significant predictors of cardiac events (relative risk = 5.3 at 1 year). Sixty-four percent of elderly patients were successfully stratified into very low and high risk subgroups, with annual cardiac event rates of <1% and >15%, respectively. The cardiac event rate in dipyridamole stress patients was 22% (24 myocardial infarction, 52 death, 42 revascularization). The cardiac event rate was significantly lower (5%) in 150 patients with a normal dipyridamole thallium-201 study (P < 0.001). Clinical univariale predictors of cardiac events were previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all P < 0.05). A fixed, reversible, or combined thallium defect pattern was correlated with cardiac death or myocardial infarction (P < 0.05). Multivariate analysis demonstrated that the presence of an abnormal dipyridamole thallium study was the single-best predictor of cardiac events (relative risk = 7.2; P < 0.01). We conclude that exercise and dipyridamole thallium-201 myocardial imaging are powerful independent noninvasive techniques for prognostication in the elderly patient population, a group with the potential for advanced coronary artery disease and a high risk of cardiac events.