Myocardial blood flow and perfusion reserve in infarcted patients with stress-induced normalization of previously negative T waves: A positron emission tomography study

Background, The clinical correlations between stress-induced normalization of previously negative T waves (NTW) and regional myocardial blood flow (MB F) regulation and tissue viability remain debatable. Methods and Results. To confirm these correlations, 14 patients with previo us anterior myocardial infarction (13 Q waves) and NTW on baseline electroc ardiographic precordial leads and 10 healthy subjects were studied by means of positron emission tomography (PET), The MBF values were obtained in the anterior infarcted myocardial regions in either resting condition or durin g dipyridamole infusion, using N-13 ammonia as a flow tracer. Seven subject s had normalization of NTW (Group 1) and 7 had persistent NTW (Group 2) dur ing dipyridamole infusion. The resting MBF values were similar for both Gro up 1 and Group 2 (0.43 +/- 0.13 versus 0.51 +/- 0.15 mL.min(-1).g(-1), resp ectively; P = not significant) and were significantly lower than in the ant erior myocardial regions of healthy subjects (1.03 +/- 0.23 mL.min(-1).g(-1 ), P <.001). After administration of dipyridamole, the MBF was significantl y higher in Group 1 than in Group 2 (0.88 +/- 0.37 versus 0.55 +/- 0.17 mL. min(-1).g(-1), respectively; P <.05) and markedly lower than in healthy sub jects (3.78 +/- 0.64 mL.min(-1).g(-1), P<.001). Coronary reserves (dipyrida mole/resting MBF) were 2.03 +/- 0.40 and 1.14 +/- 0.44 in Group 1 and Group 2, respectively (P <.002). Conclusion, Despite similar values of resting perfusion, infarcted dysfunct ional areas with or without NTW during stress may present different regiona l MBF responses; normalization of NTW demonstrates higher coronary flow res erve than persistent NTW, suggesting a better preserved coronary microcircu latory function in the former, indicative of the presence of myocardial via bility.