Spontaneous late improvement of myocardial viability in the chronic infarct zone is possible, depending on persistent TIMI 3 flow and a low grade stenosis of the infarct artery

Objective-In the chronic phase of myocardial infarction, the relation betwe en myocardial recovery and infarct related artery status remains unclear. T he spontaneous changes in rest-redistribution thallium defect size were pro spectively studied over six months in 52 patients with chronic Q wave myoca rdial infarction. Design-Changes in rest thallium defect size, thallium uptake in the infarct area, and radionuclide left ventricular ejection fraction were compared to the quantitative coronary angiogram data. Two groups of patients were cons idered: patients with a percentage of stenosis below 100% (group 1, n = 31) ; and patients with an occluded artery (group 2, n = 21). Results-In the overall population, the mean (SD) defect size decreased from 28.2 (17.2)% to 24.9 (19.3)% of the whole myocardium (p = 0.01), while, in this area, the thallium uptake increased from 62.9 (13.7)% to 66.9 (15.6)% (p < 0.001). At the time of inclusion, the defect size, thallium uptake, a nd ejection fraction were similar in both groups. In group 1 patients only, the reduction in defect size correlated with the improvement in ejection f raction (r = 0.41, p = 0.02) and was related to the percentage of coronary artery stenosis. TIMI 3 patients reduced the defect size while other patien ts increased this defect (-5.1 (7.0)% v +11.0 (14.4)%, p < 0.001). In contr ast, no significant relations were found in group 2 patients. Conclusion-Late spontaneous recovery in thallium defect can occur in patien ts with a patent infarct related artery, depending on the TIMI flow grade a nd a low grade stenosis of the infarct related artery, and is associated wi th functional improvement.