Comparison of dobutamine stress and atropine exercise stress test myocardial perfusion spect in patients with poor exercise capacity

Exercise stress test [E] is the main diagnostic stress modality used with myocardial perfusion SPECT [MPS]. However, its usefulness and accuracy depends on patient's [pt] ability to achieve target heart rate [THR], limiting its utility in pt with poor exercise capacity. We sought to study the safety and feasibility of atropine administration during exercise myocardial perfusion study [EMPS] as compared to standard dobutamine MPS. Thirty patients aged 51.4 +/- 8.3 years; 80% males referred for a diagnostic MPS study and failed to achieve their THR on E. Patients were divided in to 2 groups [G]; G I 15 pts continued E and atropine was administered in doses of 0.5 mg /min until THR achieved or ischemic ECG changes or a maximum dose of 2 mg. GII 15 patients were subjected to dobutamine MPS from the start. There was no significant difference between the two groups regarding pretest likelihood of ischemia, resting heart rate, systolic and diastolic blood pressures. All pts in GI reached THR after atropine injection. GII experienced more side effects [40% vs 0%, p=0.017]; varying from chest pain 33%, headache 6.7%, nausea and vomiting 6.7%. No difference was found in the frequency of ECG changes [37% vs 47%] or frequency of positive MPS [87% vs 80%]. Use of atropine as an adjunct to standard EMPS in pts with poor exercise capacity allows them to achieve THR and can help decrease the number of inconclusive tests. Atropine EMPS is better tolerated by than dobutamine MPS