STUDY OF MYOCARDIAL PERFUSION RESERVE WITH SINGLE-PHOTON-EMISSION COMPUTED-TOMOGRAPHY WITH TL-201 AND PHARMACOLOGICAL STRESS WITH ADENOSINE-TRIPHOSPHATE IN PATIENTS WITH CARDIOVASCULAR RISK-FACTORS

Introduction and objective. Recent studies have suggested that the eva luation of coronary reserve is a sensitive method in the early detecti on of vascular alterations before plaques exist, and certainly before clinical detection of atherosclerotic lesions. Single Photon Emission Computed Tomography (SPECT) with thallium-201 (Tl-201) provides a noni nvasive tool for evaluating myocardial perfusion reserve. The objectiv e of this study was to measure the myocardial perfusion reserve in two groups of subjects, some with and some without cardiovascular risk fa ctors and in a group of patients with coronary artery disease. Methods . Seventy-four subjects, divided into three groups, were recruited to assess regional and global myocardial perfusion reserve. The control g roup consisted of 11 asymptomatic individuals without cardiovascular r isk factors. The second group was composed of 49 patients with one or more risk factors. Finally, the third group included 14 patients with coronary artery disease. Tl-201-SPECT at rest and after pharmacologica l stress with a 7 minute adenosine triphosphate (ATP) infusion (140 mu g/kg/min) was performed in all patients. ATP minus rest value subtrac tion was applied in order to obtain the stress data. Relative myocardi al perfusion reserve indices were calculated as the ratio between stre ss and rest values. Results. Global and regional myocardial perfusion reserves of the vascular territories were significantly lower in patie nts with cardiovascular risk factors than in control subjects (Global: 1.48 +/- 0.19 vs 1.81 +/- 0.08, LAD: 1.52 +/- 0.21 vs 1.85 +/- 0.09, CX: 1.45 +/- 0.2 vs 1.79 +/- 0.86, RCA: 1.47 +/- 0.2 vs 1.79 +/- 0.86) and higher than in patients with coronary artery disease (Global: 1.4 8 +/- 0.19 vs 1.31 +/- 0.14, LAD: 1.52 +/- 0.21 vs 1.35 +/- 0.15, CX: 1.45 +/- 0.2 vs 1.2 +/- 0.24). Univariate linear regression analysis i n a group of 40 patients with high risk lipid profiles revealed a sign ificant negative correlation between myocardial perfusion reserve and total cholesterol (r = -0.35; p = 0.01), LDL-cholesterol (r = -0.38; p = 0.036) and LDL/RDL ratio (r = -0.39; p = 0.029). Conclusion. Determ ination of myocardial perfusion reserve with Tl-201-SPECT allows the d etection of abnormal vasodilatory response to intravenous ATP in patie nts with cardiovascular risk factors. These patients have higher reser ves than patients with coronary disease, which might suggest an early phase of atherosclerosis.