Cardiovascular outcomes after pharmacologic stress myocardial perfusion imaging

Background — While pharmacologic stress single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) is used for noninvasive evaluation of patients who are unable to perform treadmill exercise, its impact on net reclassification improvement (NRI) of prognosis is unknown.

Methods — We evaluated the prognostic value of pharmacologic stress MPI for prediction of cardiovascular death or non-fatal myocardial infarction (MI) within one-year at a single-center university-based laboratory. We examined continuous and categorical NRI of pharmacologic SPECT-MPI for prediction of outcomes beyond clinical factors alone.

Results — 6240 patients (median 66 years [IQR 56-74], 3466 men) were studied and followed for 5963 person-years. SPECT-MPI variables associated with increased risk of cardiovascular death or non-fatal MI included summed stress score (SSS), stress ST-shift, and post-stress resting left ventricular ejection fraction (LVEF) ≤50%. Compared to a clinical model which included age, sex, cardiovascular disease, risk factors, and medications, model χ² (210.5 vs. 281.9, p < 0.001) and c-statistic (0.74 vs. 0.78, p < 0.001) were significantly increased by addition of SPECT-MPI predictors (SSS, stress ST-shift and stress resting LVEF). SPECT-MPI predictors increased continuous NRI by 49.4% (p < 0.001), reclassifying 66.5% of patients as lower risk and 32.8% as higher risk of cardiovascular death or non-fatal MI. Addition of MPI predictors to clinical factors using risk categories, defined as <1%, 1-3%, and >3% annualized risk of cardiovascular death or non-fatal MI, yielded a 15.0% improvement in NRI (95%CI; 7.6-27.6%, p < 0.001).

Conclusions — Pharmacologic stress MPI substantially improved net reclassification of cardiovascular death or MI risk beyond that afforded by clinical factors.