Thallium-201 right lung heart ratio during exercise in patients with coronary artery disease: relation to thallium-201 myocardial single-photon emission tomography, rest and exercise left ventricular function and coronary angiography

The aim of this study was to correlate lung thallium-201 uptake on exercise with (TI)-T-201 single-photon emission tomography (SPET) myocardial perfus ion im: aging, rest and exercise equilibrium radionuclide angiographic and coronary angiographic findings in patients with coronary artery disease (CA D) using a sample, reproducible lung/heart (L/H) ratio that would be easy t o use in clinical practice. L/H ratio was defined on the anterior planar im age obtained during exercise (TI)-T-201 SPET; acquisition as the mean count s per pixel in an entire right lung field region of interest divided by the mean counts per pixel in the hottest myocardial wall region of interest. W e studied 103 patients. Fifty-nine patients (group I) with <5% likelihood o f CAD were used as a reference group. In 44 CAD patients (group II), L/H ra tio was compared with Tl-201 SPET, radionuclide angiographic and coronary a ngiographic variables. The group I L/H ratio of 0.35+/-0.05 (mean +/-1 SD) was significantly lower (P<0.001) than the group II L/H ratio of 0.45+/-0.1 0. An WH ratio >0.45 (mean + 2 SD in group I) was considered abnormal. In g roup II, WH ratio showed a significant correlation with stress and rest Tl- 201 perfusion defect size (r = 0.39 and r = 0.42, P<0.01, respectively), bu t not with extent of ischaemic myocardium. The mean WH ratio was 0.41+/-0.1 0 in patients with one; vessel disease (n = 15), 0.46+/-0.08 in those with two-vessel disease (n = 17) and 0.47+/-0.12 in those with three-vessel dise ase (n = 12), but no significant difference was found between the three sub groups. L/H ratio showed a significant inverse relation with rest and exerc ise left ventricular ejection fraction (r = -0.37 and r = -0.50, P<0.05 and P<0.001, respectively). Using stepwise multiple regression analysis, exerc ise left Ventricular ejection fraction and previous history of hypertension were the sole two variables independently predictive of the L/H ratio. In conclusion, although lung thallium uptake is usually found to correlate wit h extent and severity of CAD, increased L/H ratio should primarily be consi dered as a marker of exercise-induced left ventricular systolic and perhaps diastolic dysfunction, probably independent of the underlying cardiac dise ase.