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

Abstract

Background. The clinical correlations between stress-induced normalization of previously negative T waves (NTW) and regional myocardial blood flow (MBF) regulation and tissue viability remain debatable. Methods and Results. To confirm these correlations, 14 patients with previous anterior myocardial infarction (13 Q waves) and NTW on baseline electrocardiographic 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 during dipyridamole infusion, using N-13 ammonia as a flow tracer. Seven subjects had normalization of NTW (Group 1) and 7 had persistent NTW (Group 2) during dipyridamole infusion. The resting MBF values were similar for both Group 1 and Group 2 (0.43 ± 0.13 versus 0.51 ± 0.15 mL·min −1·g −1, respectively; P = not significant) and were significantly lower than in the anterior myocardial regions of healthy subjects (1.03 ± 0.23 mL·min −1·g −1, P < .001). After administration of dipyridamole, the MBF was significantly 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 subjects (3.78 ± 0.64 mL·min −1·g −1, P < .001). Coronary reserves (dipyridamole/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 dysfunctional areas with or without NTW during stress may present different regional MBF responses; normalization of NTW demonstrates higher coronary flow reserve than persistent NTW, suggesting a better preserved coronary microcirculatory function in the former, indicative of the presence of myocardial viability.