Submaximal exercise testing plus atropine in myocardial perfusion SPECT.

INTRODUCTION AND OBJECTIVES The aim of this study was to determine the diagnostic value of using myocardial perfusion single-photon emission computed tomography (SPECT) with intravenous atropine administration at the end of submaximal exercise testing. METHODS One milligram of atropine was administered intravenously at the end of exercise testing to 172 patients who underwent a symptom-limited ergometric test but did not reach 80% of their peak heart rate without exhibiting angina or an ST-segment depression ≥1 mm. Within 1 week, 23 patients who satisfied scintigraphic criteria for ischemia during SPECT with atropine underwent SPECT for a second time without atropine administration with the aim of comparing the presence and severity of scintigraphic ischemia between the two studies (SDS: summed difference score). RESULTS Of the 172 patients, 75 (43.6%) developed angina (n=56) or ST-segment depression (n=30) during atropine administration. Eight of the 23 patients (35%) who underwent two tests exhibited scintigraphic ischemia (SDS ≥2) on only the test with atropine. Furthermore, the SDS was significantly greater on SPECT imaging with atropine (5.6 ± 4.5 vs. 3.1 ± 2.8; P=.0001). CONCLUSIONS One-third of patients who met scintigraphic criteria for ischemia at the end of submaximal exercise testing and after atropine administration would not have met those criteria without administration of the drug.