Significance of both negative T waves and stress-induced normalization of the repolarization phase in infarcted patients: a positron-emission-tomography assessment of regulation of myocardial blood flow and viability of myocardium

Background The clinical correlation of stress-induced normalization of prev iously negative T waves (NNTW) to regulation of regional myocardial blood f low (MBF) and tissue viability is still being debated. Objective To clarify its meaning. Methods We studied 25 patients, who had previously suffered anterior myocar dial infarction and for whom negative T waves were recorded on baseline ele ctrocardiographic precordial leads, by means of positron emission tomograph y. We obtained MBF in the infarcted myocardial regions under resting condit ions for all patients, during infusion of dipyridamole (17 patients) and do butamine (20 patients), using [N-13]-ammonia as a flow tracer. Results During stress tests, 13 patients exhibited NNTW (group 1) whereas t he remaining 12 presented persistent negative T waves (group 2). NNTW was o bserved in 18 stress studies (for 10 and eight patients during administrati on of dobutamine and dipyridamole, respectively) whereas persistent negativ e T waves occurred 19 times (for 10 patients during infusion of dobutamine and nine patients during administration of dipyridamole). A complete concor dance of the modifications of the repolarization phase was observed for pat ients who were subjected both to dipyridamole and to dobutamine studies. Fu rthermore, we assessed viability of myocardium in 20 of 25 patients using [ F-18]-fluorodeoxyglucose. For the remaining five patients not subjected to metabolic imaging, a coronary reserve of 1.65 was considered a cut-off of v iability. Resting MBF for patients in groups 1 and 2 were similar (0.53 +/- 0.20 versus 0.47 +/- 0.17 ml/min per g, respectively, NS) whereas during p harmacological stress, MBF of patients in group 1 was significantly higher than that for patients in group 2 (0.99 +/- 0.41 versus 0.56 +/- 0.26 ml/mi n per g, respectively, P < 0.0001). Coronary vasodilating capability, expre ssed as stress/resting MBF ratio, turned out to be 1.88 +/- 0.49 and 1.16 /- 0.37 for patients in groups 1 and 2, respectively(P < 0.0001). We observ ed no difference in mean exercise work load (9.6 +/- 2.80 versus 8.46 +/- 2 .18 min, NS) and rate - pressure product (24 230 +/- 6425 versus 24 207 +/- 8146 mmHg beats/min, NS) at peak for the two categories of patients. All 1 3 patients in group 1 (100%) had viable myocardium in the anterior infarcte d areas whereas only one of 12 patients in group 2 did (9%, P < 0.0001 vers us group 1). Finally, a subanalysis for the specific pharmacological agent used was performed and it gave similar results. Conclusion Regardless of the specific stress test able to elicit the electr ocardiographic sign, infarcted dysfunctional areas with stress-induced NNTW were demonstrated to have a higher coronary vasodilating capability and a greater probability of viability of myocardium than had persistent negative T wave regions. Therefore, detection of NNTW appears to be a cheap first-l ine method for the identification both of a better preserved coronary micro circulatory function and of the persistence of viability of myocardium in t he infarcted areas. Coron Artery Dis 12:205-215 (C) 2001 Lippincott William s & Wilkins.