Clinical significance of hypotensive response in patients undergoing dipyridamole stress myocardial perfusion studies

Abstract

Background: We sought to study the incidence and clinical significance of hypotensive response in patients undergoing dipyridamole stress myocardial perfusion study (MPS). Methods: We identified 306 consecutive patients (mean age 68.6 ± 12 years, women 50.3%) who had dipyridamole stress MPS using dual isotope gated single photon emission computed tomography. Hypotensive response was categorised as 10% or 20% drop of systolic blood pressure (BP) from the baseline, or peak systolic blood pressure < 100 mmHg. Resting blood pressure and heart rate, peak blood pressure and heart rate, peak/rest heart rate ratio, ischemic ST changes or old myocardial infarction on electrocardiogram (ECG), left ventricular ejection fraction (LVEF), and regional myocardial ischemia or infarction (anterior and/or septal, inferior, lateral and apical region) by MPS were recorded and analysed using T-test for independent samples and Nonparametric Test (Mann-Whitney test). Results: In the study cohort, 35.6% of patients had BP drop >10%, 13.7% of patients had BP drop >20%, and 3.9% of patients had systolic BP <100 mmHg after intravenous dipyridamole infusion. The degree of hypotensive response was not related to gender, resting diastolic BP, resting heart rate, LVEF, myocardial ischemia or infarction on ECG and MPS. Patients with hypotensive response showed highly significant differences (P value <0.001) in being older (70.3 vs. 65.5 years), with higher resting systolic BP (145.9 vs. 131.7 mmHg), lower peak heart rate (84.2 vs. 91.6 beats/minute), and lower peak/rest heart rate ratio (1.26 vs. 1.36). Conclusion: Patients with hypotensive response to intravenous dipypidamole infusion probably reflected exaggerated vascular response to vasodilator challenge and an inadequate compensatory rise in heart rate as part of the aging process. This clinical feature is usually not related to underlying myocardial ischemia or decreased left ventricular systolic function, but likely due to autonomic dysfunction frequently seen in the elderly.