Independent prognostic value of left ventricular contractile reserve and chronotropic response in patients with reduced left ventricular ejection fraction undergoing vasodilator stress myocardial perfusion imaging with Rb-82 positron emission tomography

Objectives: We evaluated the prognostic value of heart rate reserve (ΔHR) and left ventricular ejection fraction reserve (ΔLVEF) among patients with systolic dysfunction. Background: Inadequate ΔHR (maximal stress HR - resting HR) and ΔLVEF (LVEF at stress - LVEF at rest) in response to stress are associated with adverse cardiac events. However, the significance of an abnormal ΔHR and ΔLVEF in patients with systolic dysfunction has not been described. Methods and results: We performed a retrospective analysis of patients with rest LVEF < 45% who underwent dipyridamole stress-rest gated Rb-82 PET myocardial perfusion imaging (PET-MPI) at the Cleveland Clinic between 2006 and 2009. Stress LVEF and volumes were calculated using commercially available software (4DM). A Cox proportional hazards model (CPH) was used to examine the association between ΔLVEF, ΔHR, and all-cause death (ACD). Among 461 patients (mean age 65.7 ± 11.3 years, 82% men) 167 experienced ACD (median follow-up 1045 days). Survival was reduced among patients with ΔHR < 0 (1090 vs. 1300 days, P = 0.04) and ΔLVEF < 0 (1002 vs. 1057 days, P = 0.03). In a CPH after adjusting for confounding variables, ΔHR ≤ 0 and ΔLVEF ≤ 0 were associated with reduced survival (hazard ratio 0.93, P < 0.01 and 0.84, P = 0.01, respectively) with an interaction between age and ΔHR (χ2 = 8.1, P < 0.01). Our model predicts that the magnitude of ΔHR is associated with improved survival among younger patients. For any given ΔLVEF the magnitude of ΔHR has a greater positive effect on survival among younger patients. Conclusion: Both ΔHR and ΔLVEF during pharmacologic stress PET-MPI provide incremental value in predicting ACD among patients with systolic dysfunction.