[Usefulness of washout rate analysis in adenosine triphosphate-stress thallium-201 myocardial scintigraphy in patients with vasospastic angina].

OBJECTIVES This study evaluated the usefulness of washout rate analysis in adenosine triphosphate(ATP) stress thallium-201 scintigraphy for the diagnosis of vasospastic angina. METHODS This study included 76 patients with vasospastic angina and 18 normal controls undergoing coronary arteriography. If significant coronary artery stenosis (> or = 50%) was pointed out, the subject was excluded from this study. 111 MBq of thallium-201 was intravenously injected 3 min after ATP loading (0.16 mg/kg/min) was started. Single photon emission computed tomography (SPECT) was performed 10 min and 4 hr after intravenous injection of ATP. The mean washout rate (%) was calculated based on a bull's eye map and was divided into 3 regions, the antero-septal/lateral/inferior regions. The washout rate in each region was calculated. Regional uptake was visually estimated based on the 17 segments of SPECT images. RESULTS The washout rate in the normal control group was 48.9 +/- 4.1 (mean +/- SD)%. In patients with vasospastic angina, the washout rate in areas with coronary vasospasm was 33.4 +/- 5.5%. This value was significantly lower than in the areas without coronary vasospasm (42.8 +/- 3.6%). The usefulness of washout rate analysis in the diagnosis of vasospastic angina with a cut-off value of less than -2SD from normal washout rate in the 3 regions was examined. A significantly higher diagnostic value was found by washout rate analysis (sensitivity 72.3%, specificity 79.7%, and accuracy 74.6%) compared with visual evaluation of early images (sensitivity 50.3%, specificity 73.9%, and accuracy 57.5%). CONCLUSIONS The diagnostic value of washout rate analysis was significantly higher (73.1%) compared with visual evaluation of early images (50.3%) in patients with multivessel vasospastic angina.