Mortality Prediction in Veterans: Myocardial Perfusion Imaging
Background No data exist comparing outcome prediction from arm exercise vs pharmacologic myocardial perfusion imaging (MPI) stress test variables in patients unable to perform treadmill exercise.
Methods In this retrospective study, 2,173 consecutive lower extremity disabled veterans aged 65.4 ± 11.0 years (mean ± SD) underwent either pharmacologic MPI (1730 patients) or arm exercise stress tests (443 patients) with MPI (n = 253) or electrocardiography alone (n = 190) between 1997 and 2002. Cox multivariate regression models and reclassification analysis by integrated discrimination improvement (IDI) were used to characterize stress test and MPI predictors of cardiovascular mortality at ≥10-year follow-up after inclusion of significant demographic, clinical, and other variables.
Results Cardiovascular death occurred in 561 pharmacologic MPI and 102 arm exercise participants. Multivariate-adjusted cardiovascular mortality was predicted by arm exercise resting metabolic equivalents (hazard ratio [HR] 0.52, 95% CI 0.39–0.69, P < .001), 1-minute heart rate recovery (HR 0.61, 95% CI 0.44–0.86, P < .001), and pharmacologic and arm exercise delta (peak-rest) heart rate (both P < .001). Only an abnormal arm exercise MPI prognosticated cardiovascular death by multivariate Cox analysis (HR 1.98, 95% CI 1.04–3.77, P < .05). Arm exercise MPI defect number, type, and size provided IDI over covariates for prediction of cardiovascular mortality (IDI = 0.074–0.097). Only pharmacologic defect size prognosticated cardiovascular mortality (IDI = 0.022).
Conclusions Arm exercise capacity, heart rate recovery, and pharmacologic and arm exercise heart rate responses are robust predictors of cardiovascular mortality. Arm exercise MPI results are equivalent and possibly superior to pharmacologic MPI for cardiovascular mortality prediction in patients unable to perform treadmill exercise.
In recent years, ≥50% of the more than 5 million myocardial perfusion imaging (MPI) stress tests conducted annually in the United States have been pharmacologic studies because of comorbidities such as obesity, lung disease, and lower extremity disabilities precluding leg exercise. We have recently reported that arm exercise electrocardiographic (ECG) stress testing is a feasible alternative to pharmacologic evaluations in a high-risk veteran population and provides powerful prognostic and diagnostically important information at much lower cost and without radiation. We also demonstrated the role of arm exercise MPI for prognostication of all-cause mortality. However, there are no comparative studies of outcome prediction with arm exercise vs pharmacologic MPI. Data are also limited for the long-term prognostic role of pharmacologic MPI in high-risk populations such as veterans. The purposes of this study were to characterize physiologic, symptomatic, ECG, and MPI responses to arm exercise and pharmacologic stress in high-risk patients unable to perform leg exercise and to investigate and compare the use of these alternative stress test modalities to predict long-term cardiovascular mortality.
Abstract and Introduction
Abstract
Background No data exist comparing outcome prediction from arm exercise vs pharmacologic myocardial perfusion imaging (MPI) stress test variables in patients unable to perform treadmill exercise.
Methods In this retrospective study, 2,173 consecutive lower extremity disabled veterans aged 65.4 ± 11.0 years (mean ± SD) underwent either pharmacologic MPI (1730 patients) or arm exercise stress tests (443 patients) with MPI (n = 253) or electrocardiography alone (n = 190) between 1997 and 2002. Cox multivariate regression models and reclassification analysis by integrated discrimination improvement (IDI) were used to characterize stress test and MPI predictors of cardiovascular mortality at ≥10-year follow-up after inclusion of significant demographic, clinical, and other variables.
Results Cardiovascular death occurred in 561 pharmacologic MPI and 102 arm exercise participants. Multivariate-adjusted cardiovascular mortality was predicted by arm exercise resting metabolic equivalents (hazard ratio [HR] 0.52, 95% CI 0.39–0.69, P < .001), 1-minute heart rate recovery (HR 0.61, 95% CI 0.44–0.86, P < .001), and pharmacologic and arm exercise delta (peak-rest) heart rate (both P < .001). Only an abnormal arm exercise MPI prognosticated cardiovascular death by multivariate Cox analysis (HR 1.98, 95% CI 1.04–3.77, P < .05). Arm exercise MPI defect number, type, and size provided IDI over covariates for prediction of cardiovascular mortality (IDI = 0.074–0.097). Only pharmacologic defect size prognosticated cardiovascular mortality (IDI = 0.022).
Conclusions Arm exercise capacity, heart rate recovery, and pharmacologic and arm exercise heart rate responses are robust predictors of cardiovascular mortality. Arm exercise MPI results are equivalent and possibly superior to pharmacologic MPI for cardiovascular mortality prediction in patients unable to perform treadmill exercise.
Introduction
In recent years, ≥50% of the more than 5 million myocardial perfusion imaging (MPI) stress tests conducted annually in the United States have been pharmacologic studies because of comorbidities such as obesity, lung disease, and lower extremity disabilities precluding leg exercise. We have recently reported that arm exercise electrocardiographic (ECG) stress testing is a feasible alternative to pharmacologic evaluations in a high-risk veteran population and provides powerful prognostic and diagnostically important information at much lower cost and without radiation. We also demonstrated the role of arm exercise MPI for prognostication of all-cause mortality. However, there are no comparative studies of outcome prediction with arm exercise vs pharmacologic MPI. Data are also limited for the long-term prognostic role of pharmacologic MPI in high-risk populations such as veterans. The purposes of this study were to characterize physiologic, symptomatic, ECG, and MPI responses to arm exercise and pharmacologic stress in high-risk patients unable to perform leg exercise and to investigate and compare the use of these alternative stress test modalities to predict long-term cardiovascular mortality.