Reduced Heart Rate Response during Drug-Induced Stress Is Related to the Severity of Perfusion Defect

Introduction: During the pharmacological stress test with dipyridamole, a normal hemodynamic response is slightly reduced blood pressure and raised heart rate (HR). However, sometimes the HR response is reduced. This study investigated the relationship between the HR response during the dipyridamole stress test and the severity of the perfusion defects using Thallium 201 myocardial perfusion imaging. Methods: We enrolled 50 patients undergoing dipyridamole stress at the nuclear cardiology Lab, Main University Hospital of Alexandria. Standard dipyridamole protocol (infusion over 4 min) and standard thallium 201 protocol (2 min after dipyridamole infusion) were followed. If the heart rate (HR) ratio (peak HR/rest HR) was 1.20 or less, it was considered a reduced response. Total perfusion defect (TPD), summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) for myocardial perfusion were calculated. Patients with reduced HR response and normal HR responses were compared and independent predictors of reduced HR response were determined. Results: About 56% of patients had reduced HR response;which included a high number of patients with a history of dyslipidemia and diabetes mellitus. The reduced HR response group showed lower SSS, SRS. The analysis showed that the independent predictors of reduced HR response were rest HR, SSS, and diabetes mellitus. Conclusions: Reduction in the HR response during the dipyridamole-induced stress test is related to the severity of perfusion defect, diabetes mellitus, and Dyslipidemia.