Comparative Predictors of Mortality Risk in Contemporary Patients Referred for Stress Myocardial Perfusion Imaging

Objective: To assess the relative predictors of mortality risk in a contemporary cohort of patients referred for stress single-photon emission computed tomography myocardial perfusion imaging in whom all relevant risk factors and cardiac-related comorbidities were evaluated at the time of cardiac stress testing. Methods: We evaluated 15,662 patients undergoing stress single-photon emission computed tomography myocardial perfusion imaging between 2008 and 2017. Patients were observed for a median of 6.7 years for all-cause mortality. Patients were assessed for their mode of stress testing (exercise vs pharmacologic testing), myocardial ischemia, coronary artery disease risk factors, and cardiac-related comorbidities, such as chronic kidney disease. Results: Age and pharmacologic stress testing, which was performed in 48.1% of our patients, were the most potent predictors of mortality. Moderate to severe myocardial ischemia, a traditional driver of mortality, was present in only 3.6% of patients. There was a stepwise increase in annualized mortality according to patients’ number of risk factors (P < .001) or comorbidities (P < .001). After stratification of patients according to their mode of stress testing, this stepwise relationship of multimorbidity to mortality was noted only in pharmacologically tested patients. By contrast, the annualized mortality risk of patients undergoing treadmill exercise not only was low (<1%/year) but remained so even for patients with a high degree of multimorbidity. Conclusion: Patients referred for cardiac stress testing manifest a stepwise increase in mortality risk with an increasing burden of coronary artery disease risk factors and concomitant comorbidities. However, this stepwise increase is not observed in patients who perform treadmill exercise at the time of cardiac stress testing.