Incremental prognostic value of the hemodynamic gain index in patients undergoing exercise stress myocardial perfusion imaging.

Normal exercise single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) findings are associated with a favorable prognosis, but residual risk remains heterogeneous. The hemodynamic gain index (HGI), derived from the relative increase in rate-pressure product from rest to peak exercise, may provide complementary prognostic information. This dual-center retrospective cohort included 1254 patients with suspected or known coronary artery disease undergoing exercise SPECT-MPI. The primary endpoint was major adverse cardiovascular events (MACE), comprising all-cause death, nonfatal myocardial infarction, hospitalization for unstable angina, and late revascularization. A secondary endpoint excluded unstable angina. Mixed-effects Cox models assessed independent and incremental prognostic value. During a median follow-up of 63 months, 187 patients (14.9%) experienced MACE. HGI showed negligible correlation with stress total perfusion deficit (TPD) (ρ = 0.012, P = 0.675). Each 1-SD increase in HGI was associated with a lower MACE hazard (HR, 0.748; 95% CI, 0.623-0.898; P = 0.002). Adding HGI to a model containing stress TPD improved model fit (Δχ2 = 9.71, P = 0.002), C-index (ΔC-index = 0.006, P = 0.046), and continuous net reclassification improvement (0.310, P = 0.010). Among patients with stress TPD less than 5%, 5-year MACE-free survival was 92.1% with high HGI and 80.1% with low HGI. Incremental discrimination became significant at 24 months and was greatest at 60 months. HGI provided independent and incremental prognostic information beyond stress perfusion imaging and stratified longer-term risk among patients with stress TPD less than 5%. Its prognostic performance in patients receiving cardioactive medications requires further validation.