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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.