THE ATROPINE FACTOR IN PHARMACOLOGICAL STRESS ECHOCARDIOGRAPHY

Objectives. This study sought to compare, head to head, the two most p opular pharmacologic stress echocardiographic tests-dipyridamole and d obutamine-with state of the art protocols in a large multicenter prosp ective study. Background. In the continuing quest for ideal diagnostic accuracy, pharmacologic stress echocardiography has quickly moved ove r the years from low to high dose regimens and is currently performed with atropine coadministration. Methods. Dobutamine (up to 40 mu g/kg body weight per min) plus atropine (up to 1 mg over 4 h) and dipyridam ole (up to 0.84 mg/kg per min over 10 h) plus atropine (up to 1 mg ove r it h) stress echocardiography was performed on different days, in ra ndom order and within 1 week in 360 patients with chest pain syndrome. Thirteen different echocardiographic laboratories, all fulfilling qua lity control criteria for stress echocardiographic reading, contribute d to the study. Results. No major complications occurred during either test. The test was interrupted before achievement of predetermined en d points for limiting side effects in 37 dobutamine-atropine and 7 dip yridamole-atropine stress echocardiographic studies (feasibility 90% v s. 98%, p < 0.01). Diagnostic accuracy was assessed in a subset of 110 patients with no obvious rest dyssynergy (akinesia or dyskinesia) who underwent coronary angiography independently of test results and with in 1 week of testing. Significant coronary artery disease (greater tha n or equal to 50% diameter reduction in at least one major coronary ve ssel by quantitative coronary angiography) was found in 92 patients. S ensitivity for detection of coronary artery disease was 83% (77 of 92) for dobutamine-atropine and 82% (75 of 92) for dipyridamole-atropine stress echocardiography (p = NS), with a specificity of 89% (16 of 18) for dobutamine-atropine and 94% (17 of 18) for dipyridamole-atropine stress echocardiography (p = NS). A significant correlation was presen t between peak wall motion score index during dipyridamole-atropine an d dobutamine-atropine stress echocardiography (r = 0.83, p < 0.0001). Conclusions. Dobutamine-atropine and dipyridamole-atropine stress echo cardiography are safe and feasible, although submaximal studies are mo re frequent with dobutamine. The two stresses have comparable accuracy in the detection of angiographically assessed coronary artery disease , although dobutamine is marginally more sensitive and dipyridamole ma rginally more specific. Stratification of the ischemic response in the space domain is also comparable with the two stresses.