Critically ischemic myocardium in clinically stable patients following thrombolytic therapy for acute myocardial infarction: Potential implications for early coronary angioplasty in selected patients

Abstract

The utility of post-thombolysis, rest-redistribution thallium (TI)-201 scintigraphy was studied in 32 patients with a first myocardial infarction who were clinically stable following reperfusion. Day 1 scintigraphy obtained 5 ± 4 hours (range 1 to 16) after thrombolysis revealed an average perfusion defect of 6.5 ± 2.6 segments (range 1 to 11). There was a total of 208 abnormal segments, 137 of which were nonreversible at 4 hours, 50 of which were fully or partially reversible, and 21 of which had a reverse redistribution pattern. Repeat TI-201 scintigraphy on day 10 revealed significantly smaller perfusion defects of 4.9 ± 2.4 segments (range 0 to 9) with improvement predominantly of the day 1 reversible segments, and the improvement in segmental perfusion correlated with better regional left ventricular function. Twenty-nine (58%) of the 50 reversible segments normalized by day 10, and 11 (22%) improved, whereas only 16 (12%) of 137 nonreversible segments had normalized by day 10, only 9 had (6%) improved and 112 (82%) were unchanged ( p < 0.001 reversible versus nonreversible). There was no significant change in segments with a pattern of reverse redistribution. The improvement of reversible segments was greater in the 16 patients who underwent coronary angioplasty (PTCA) during the interval between the two scintigrams than in the 16 who did not. All 24 reversible segments in the PTCA group improved or normalized by day 10 compared with 16 (62%) of 26 reversible segments in the No PTCA group ( p < 0.001). Furthermore, 8 of the 10 reversible segments in the No PTCA group that did not improve actually deteriorated and became nonreversible by day 10. The minor improvement of nonreversible segments was not related to PTCA. Consistent with the findings in individual segments, the 19 patients with a reversible component on the day 1 TI-201 scintigram had significantly greater improvement in perfusion defect by day 10 than the 13 patients without a reversible component (37 ± 33% versus 7 ± 22% decrease in perfusion defect severity, p < 0.05), and this improvement was greatest in the 10 patients with a reversible component who underwent PTCA. In contrast, PTCA had no impact on the perfusion defect in the 13 patients without a reversible component. Our data suggest that following thrombolytic therapy for acute myocardial infarction, viable myocardium in the reperfused zone may remain ischemic, as manifested by a reversible pattern of TI-201 redistribution at rest, and thus may be in jeopardy of gradual progression to necrosis. Since PTCA appeared to prevent necrosis in these “critically ischemic” or “moribund” myocardial segments, out findings may have implications for the early recognition of a subgroup of patients who may benefit from post-thrombolysis PTCA of the residual stenosis of the artery of infarction.