Different Degrees of Ischemic Threshold Stratified by the Dipyridamole-Echocardiography Test EUGENIO PICANO, MD, FABIO LATTANZI, MD, MICHELE MASINI, MD, ALESSANDRO DISTANTE, MD, and ANTONIO L'ABBATE, MD Dipyridamole-echocardiography (echo) testing, ex- ercise stress testing and coronary arteriography were performed in 141 patients with effort chest pain. Patients were separated into 5 groups accord- ing to the dose of dipyridamole needed to induce is- chemia (0.56 mg/kg over 4 minutes vs 0.84 mg/kg over 10 minutes) and to the time of onset of the asynergy with the small dose (within vs beyond 3 minutes after the end of dipyridamole administra- tion): group 1--early positive response to a small dose (33 patients); group 2--1ate positive response to a small dose (29 patients); group 3mnegative response to a small dose, positive response to a large dose (17 patients); group 4a---negative re- sponse to both large and small doses, with signifi- cant coronary artery disease (CAD) (32 patients); and group 4b--negative response to small and large doses, without CAD (30 patients). All patients in groups 1, 2 and 3 had significant CAD. The rate- pressure product on exercise stress testing was measured at 0.10 mV of ST-segment shift in pa- tients with a positive response and at peak exercise in patients with a negative response. Rate-pressure product significantly separated group 1 and group 2 from each other (157 4- 46 and 229 4- 33 mm Hg X beats/min X 1/100, respectively, mean 4- stan- dard deviation) and from group 3, group 4a and group 4b (284 4- 40, 290 4- 51, and 298 4- 45 mm Hg X beats/min X 1/100); values in the 3 lat- ter groups overlapped. Thus, the dipyridamole-echo test can stratify groups of patients with different lev- els of ischemic threshold on effort. (Am J Cardiol 1987;59:71-73) The dipyridamole-echocardiography (echo} test has been proposed as a useful tool in evaluation of patients with coronary artery disease. 1-6 A major limitation of the dipyridamole-echo test is that it gives an "all-or- none" response {positivity vs negativity}, while the ex- ercise stress test {EST} offers a grading of the ischemic response, assessed through the work threshold at which ischemia occurs. Such graded response is of paramount clinical value because "the intensity of car- diac work at which ischemia occurs is even more im- portant than its presence. ''7 We tested whether the dipyridamole-echo test can stratify different degrees of coronary reserve impair- ment. To this goal, a few simple variables were consid- From the C.N.R. Clinical Physiology Institute, University of Pisa, Pisa, Italy. Dr. Picano is an A.R.MED. research fellow for ultrasonic diagnosis of atherosclerosis. Manuscript received May 22, 1986; revised manuscript received August 22, 1986, ac- cepted August 25, 1986. Address for reprints: Eugenio Picano, MD, Istituto di Fisiolo- gia Clinica del CNR, Via Savi, 8; 56100, Pisa, Italy. ered in the dipyridamole-echo test response: presence of asynergy {positivity vs negativity of the test re- sponse); dose of dipyridamole required to induce is- chemia (small vs large); and for the small dose only, timing of onset of the asynergy. The dipyridamole- echo test response was evaluated for each patient against a physiologic reference standard: maximal or "ischemic" rate-pressure product value on EST. Methods Selection of patients: One hundred forty-one pa- tients with effort chest pain who had undergone EST, the dipyridamole-echo test and coronary angiography were enrolled in the study. Mean age was 55 years (range 35 to 67}. Patients who had attacks of angina at rest during the hospitalization period, after therapeu- tic washout, were not included, because in these pa- tients a variable functional factor {not detectable by the dipyridamole-echo test) may heavily modulate the response to exercise. 8 Patients with concomitant conditions that can cause "nonischemic" effort-induced ST-segment shift (arte- rial hypertension, conduction disturbances, left ven- 71