Usefulness of a High-Dose Dipyridamole- Echocardiography Test for Diagnosis of Syndrome X EUGENIO PICANO, MD, FABIO LAlTANZI, MD, MICHELE MASINI, MD, ALESSANDRO DISTANTE, MD, and ANTONIO L’ABBATE, MD This study assesses whether the high-dose dipyrida- mole-echocardiography test (DET, 2-D echocardio- graphic and 12-lead electrocardiographic monitoring during dipyridamole infusion, up to 0.84 mg/kg over 10 minutes) can help to identify patients with syn- drome X. DET was performed in 10 control subjects (group A) and in 19 patients with syndrome X (group B). Patients in group B had chest pain on ef- fort, a positive exercise stress response (more than 0.1 mV of ST-segment depression), negative ergo- novine test response and normal left ventricular function and coronary angiographic findings. During DET no subject in group A showed transient asyner- gy or ST-segment depression and none had chest pain; in group B, no patient had transient asynergy, 13 (88%) had chest pain and 18 (84 %) had more than 0.1 mV of ST-segment depression. Percent fractional shortening was not significantly different in the 2 study groups, either basally (group A, 35 f 7; group B, 37 f 8) or at peak hyperkinesia during DET (group A, 48 f 8; group B, 54 f 10). Thus, dipyridamole-induced chest pain and ST-segment depression in patients with syndrome X are not as- sociated with impaired regional or global left ven- tricular function. This entity of echocardiographically silent myocardial ischemia during DET may be a clue to noninvasive detection of syndrome X. (Am J Cardiol 1987;60:508-512) P atients with syndrome X represent a complex medi- cal problem. Despite their typical ischemic response to the exercise stress test, they show a normal coronary artery tree. As an explanation for this apparent para- dox, it was documented that myocardial ischemia and angina can occur in these patients as the result of inad- equate vasodilator reserve.l The site of abnormally elevated resistance is usually believed to be at the arteriolar or the prearteriolar small vessel level,2 which is not visualized by coronary arteriography. Di- pyridamole infusion has been proposed as a provoca- tive test for detection of coronary artery disease, in combination with l&lead electrocardiographic moni- toring,3,4 thallium-201 imaging5r6 or, more recently, 2- dimensional echocardiography.7J In particular, the mechanical response of the left ventricle during dipy- ridamole-echocardiography test (that is, the appear- ance of a transient asynergy of contraction) has been From the C.N.R. Clinical Physiology Institute, University of Pisa, Pisa, Italy. Manuscript received April 29, 1987, accepted May 3,1987. Address for reprints: Eugenio Picano, MD, Istituto di Fisiolo- gia Clinica de1 CNR, Via Savi, 8, 56100, Pisa, Italy. correlated to physiologic impairment in coronary flow reserve.g We assessed whether dipyridamole-echocar- diography test plays a role in noninvasive identifica- tion of these patients. Methods Selection of patients: Group A (control subjects): A control group of 10 men (aged 20 to 25 years) was studied. All were asymptomatic, had normal rest and exercise electrocardiographic findings, no family his- tory of coronary artery disease and no other coronary risk factor. Group B (patients with syndrome X): Nineteen pa- tients, aged 38 to 63 years [mean 50) (5 men, 14 women), were studied. All patients had chest pain on effort, positive exercise stress responses, negative ergonovine test results, normal global and regional systolic func- tion at baseline (by echocardiography and ventriculog- raphy] and normal coronary arteriographic findings [also without minimal luminal irregularities). No pa- tient had left bundle branch block; 8 patients had angi- na at rest. Exercise stress test: Patients performed a multi- stage bicycle ergometer test in the sitting position, with 508