Prognostic implications of stress modality on mortality risk and cause of death in patients undergoing office-based SPECT myocardial perfusion imaging

Patients requiring vasodilator single-photon emission computed-tomography myocardial perfusion imaging (spect-mpi) have a higher mortality risk than those selected for exercise or vasodilator with low-level exercise spect-mpi. however, it is unknown whether the increased mortality is driven by cardiac deaths alone or cardiac and non-cardiac deaths. in a prospective cohort of 1,511 consecutive patients referred for spect-mpi, patients were classified according to stress test modality: exercise, adenosine with low-level exercise (adenoex), and adenosine. subjects were followed for events of all-cause mortality and cause of death. survival analyses using multivariate cox regression and propensity score matching methods were performed. during a follow-up of 4.9 ± 0.9 years, a total of 68 (4.5%) deaths occurred: 50 non-cardiac and 18 cardiac. the adenosine group had the highest annual mortality (all-cause 3.65%, non-cardiac 2.36%, cardiac 1.29%), while exercise stress had the lowest mortality (all-cause 0.42%, non-cardiac 0.37%, cardiac 0.05%) and adenoex had an intermediate mortality (all-cause 1.3%, non-cardiac 0.91%, cardiac 0.39%); all p values <0.001. the majority of non-cardiac deaths were attributed to cancer. using exercise stress as a reference standard, multivariable cox regression analyses demonstrated that adenosine stress was independently predictive of all-cause mortality [hr 3.23 (ci 1.77-5.88); p < 0.001], non-cardiac death [hr 2.67 (ci 1.34-5.31); p = 0.005], and cardiac death [hr 6.30 (ci 1.55-25.56); p = 0.010] after adjusting for univariate predictors of mortality. these findings were consistent in the subgroups of patients with normal and abnormal mpi. adenoex was predictive of all-cause, non-cardiac, and cardiac deaths in univariate analysis, but it was not predictive by multivariate analysis. propensity score matched cohort analysis showed that the adenosine stress group had the highest all-cause (p < 0.001), non-cardiac (p = 0.013), and cardiac deaths (p < 0.001), while the exercise stress group had the lowest mortality of any cause. the inability to perform any level of exercise during a spect-mpi stress is associated with high mortality risk, which is derived from both cardiac and non-cardiac deaths.