Detecçäo do miocárdio viável: estudo de perfusäo, antes e após a cirurgia de revascularizaçäo em portadores de infarto do miocárdio / Detection of the viable myocardium: a perfusion scintigraphic study, before and after coronary bypass surgery in myocardial infarction patients

ABSTRACT

Objective - To compare single-photon-emission computed tomography (SPECT) imaging scans using (201)Tl and (99m)Tc-MIBI in detection of viable myocardium, in regions compromised by infraction. Methods - Thirty-two (59.3+9.8 years old and 87 per cent male) myocardial infarction patients were studied. All had Q waves on the ECG and left ventricle ejection fraction of <50 per cent. They underwent coronary and left ventricle angiographies and SPECT before (including (201)Tl reinjection) and after coronary artery bypass surgery (CABG). Improvement in perfusion observed after surgery was considered the gold standard for myocardial viability. Results - Among 102 studied regions of the heart, there were 40 (39.2 per cent) areas of transient perfusion defects in the conventional protocol with (201)Tl and 52 (51.0 per cent) after reinjection. Therefore, 12/62 (19.4 per cent) more viable regions were identified by reinjection. Using (99m)Tc-MIBI, only 14 (13.7 per cent) regions with transient defects were identified, all of which were seen also in (201)Tl protocols. After surgery, 49 of total of 93 regions analyzed (52.7 per cent) were viable. Sensitivity, specificity, accuracy, positive and negative prediction values were, respectively, (201)Tl SPECT scans-65.3 per cent, 90.9 per cent, 77.4 per cent, 88.9 per cent and 70.2 per cent, reinjection protocol with (201)Tl scans - 81.6 per cent, 81.8 per cent, 81.7 per cent, 83.3 per cent and 80.0 per cent; (99m)Tc-MIBI SPECT scans - 20.4 per cent, 90.9 per cent, 53.8 per cent, 71.4 per cent and 50.6 per cent. Logistic regression demonstrated that the reinjection protocol with (201)Tl was the best predictor of viability (P<0.001). Conclusion - Our data suggest the election of (201)Tl for viability studies, especially when using the reinjection protocol.