Correlation of heart rate response to dipyridamole stress during SPECT myocardial perfusion imaging with clinical factors

Introduction: Myocardial perfusion imaging (MPI) with pharmacologic stress is a useful technique for evaluation of suspected coronary artery disease (CAD). Heart rate responses (HRR) to vasodilators such as dipyridamole mirror autonomic activity and may provide important prognostic information in CAD patients. In this study, the impact of baseline characteristics of patients including age and gender on the expected HRR has been assessed. Methods: This retrospective study included database of 2584 patients (1575 female, 1009 male) who were referred to the nuclear medicine department for pharmacologic MPI. The HRR to dipyridamole was calculated as ratio of maximal heart rate (HR) during or shortly after dipyridamole infusion to baseline HR. The association of HRR with age, gender, presence of other known CAD risk factors and perfusion findings was evaluated. Results: Significant correlation was found between HRR and sex, age, diabetes mellitus (DM), hypertension (HTN), and chronic kidney disease (CKD) (P < 0.001) in both univariate and multivariate analysis. The mean HRR was also significantly higher in patients with normal perfusion on SPECT MPI as compared to patients with abnormal findings, however, multivariate regression analysis showed no significant correlation. In the subgroup of patients with no CAD risk factors, HRR was significantly higher in women under age 55 years. Conclusion: The HRR during dipyridamole infusion depends on age and gender, irrespective of presence of other CAD risk factors and should be considered in the interpretation of. Besides, DM, HTN and CKD are also correlated with lower HRR to dipyridamole stress.