Blunted heart rate response as a predictor of cardiac death in patients undergoing vasodilator stress technetium-99m sestamibi gated SPECT myocardial perfusion imaging

Introduction: The prognostic value of a blunted heart rate response (BHR) during ECG-gated vasodilator stress SPECT MPI in relation to ventricular function on long-term cardiovascular events is not well established. We performed this study to evaluate the incremental prognostic value of BHR during pharmacological stress SPECT MPI. Methods: Consecutive patients who underwent dipyridamole stress Tc-99m sestamibi ECG-gated SPECT MPI (without exercise) were identified. The ratio of peak stress heart rate to baseline was noted. If the ratio was <1.20, it was considered blunted (BHR). The images were interpreted using the standard ASNC 17 segment model. Patients were followed up for a mean time period of 2.3 ± 1.5 years. Results: Sixty-four percent (2,890/4,484) of patients demonstrated BHR during dipyridamole stress testing. Cardiac death, the primary end point, occurred in 6.8% of patients. Patients with BHR had a significantly lower cardiac death-free survival as compared to NO BHR group in total population (83% vs 94%; P <.001) as well as in subgroup with normal ejection fraction (89% vs 96%; P <.001). BHR was an independent predictor of cardiac death after adjusting for multiple clinical, perfusion, and function-related gated SPECT variables. Conclusion: Blunted heart rate response during vasodilator stress SPECT MPI is an important prognostic marker for cardiac death.