The use of dobutamine stress thallium scintigraphy in the diagnosis of syndrome X.

Dobutamine stress thallium scintigraphy is a non-exercise stress technique used in the assessment of myocardial ischaemia. Non-exercise techniques are independent of the patient's exercise capacity or the subjective development of limiting symptoms. Preliminary data are presented regarding the effects of graded infusions of dobutamine (maximum 20 micrograms/kg/min) in seven consecutive patients with syndrome X. The dobutamine stress test caused significant increases in mean heart rate (rest 65.4 beats/min, peak dobutamine infusion 112.4 beats/min, P < 0.001) and systolic blood pressure (rest 138.6 mmHg, peak dobutamine infusion 166.7 mmHg, P = 0.002) and provoked typical symptoms in all the patients. Single photon emission computerized tomography was performed and the mean number of reversible defects was 1.86 per patient (range 1-3). One patient developed transient atrial fibrillation during the dobutamine infusion but there were no complications in the remainder of the study group. It is concluded that dobutamine-thallium scintigraphy in patients with syndrome X is safe, reproduces patients symptoms' reliably and presents a controllable degree of stress to the cardiovascular system. The consistent demonstration of a reversible perfusion defect in patients with syndrome X is evidence of abnormal myocardial physiology. This criterion could be added to those currently used to define syndrome X in order to improve objectively the identification of this patient group.