ASSESSMENT OF QUANTITATIVE EXERCISE TL-201 EMISSION COMPUTED-TOMOGRAPHY IN PATIENTS WITH VASOSPASTIC ANGINA - VALUE OF WASHOUT RATE ANALYSIS

This study was performed to assess the value of washout rate analysis of quantitative exercise thallium-201 emission computed tomography in vasospastic angina patients without significant coronary stenosis. Qua ntitative analysis of both thallium-201 perfusion and washout rate bef ore and after drug treatment was performed in 48 patients with vasospa stic angina and no significant coronary artery stenosis. All of the pa tients attained more than 90% of their age-predicted heart rate during each exercise test. Before drug treatment, 26 patients exhibited exer cise-induced ischemia (perfusion defects on stress polar map), 17 did not exhibit exercise-induced ischemia (normal stress and washout rate polar maps), and the remaining 5 patients showed no perfusion defects, but did show extensive abnormal washout rates. On coronary angiograph y, multivessel coronary spasm was documented in 12 of the 26 patients with exercise-induced ischemia, in 7 of the 17 patients without exerci se-induced ischemia and in 4 patients with an extensive abnormal washo ut rate and a normal stress polar map. In the 17 patients without exer cise-induced ischemia, the mean washout rate was significantly decreas ed (p<0.05) in association with a significant decrease in the double p roduct (p<0.05) after drug treatment. Of the 26 patients with exercise -induced ischemia, 18 (group 1) showed an increase in the mean washout rate with improved perfusion defect after drug treatment. The remaini ng 8 patients (group 2) showed a decrease in the mean washout rate wit h improved perfusion defect after drug treatment, which increased sign ificantly on repeat exercise test performed after additional increased doses of antianginal drugs were administered (p<0.01). The number of patients with multivessel coronary spasm was significantly high in gro up 2 (p<0.01). Thirteen patients showed an extensive abnormal washout rate before drug treatment, including 8 patients with exercise-induced ischemia and 5 patients with no perfusion defects, who showed an incr eased mean washout rate after drug treatment (p<0.05). These findings indicate that washout rate analysis aids in the diagnosis in vasospast ic angina patients with exercise-induced ischemia. Some patients with exercise-induced ischemia can not be detected by thallium-201 perfusio n analysis alone, especially those with multivessel coronary spasm and when this procedure is performed after drug treatment. In addition, a high frequency of abnormal washout rate in vasospastic angina may res ult not only from exercise-induced ischemia due to main epicardial cor onary artery spasm, but also from microspasm, or impairment of microci rculation or myocyte.