Decreased QTc dispersion after coronary revascularization: relationships with the quantitative degree of improvement in myocardial ischemia

ABSTRACT

OBJECT & METHOD: Thirty-four patients (mean age 58.1+/-8.3 years, MF=113) with angina in the absence of previous myocardial infarction, who underwent percutaneous coronary intervention (stenting and/or balloon PTCA, n=5) or coronary arterial bypass grafting (CABG, n=) were evaluated to assess the relationships between the degree of improvement in myocardial dipyridamole Tl-201 SPECT and the degree of decrease in QTc dispersion after coronary revascularization. QTc dispersions were measured manually using digitizer by a single observer from ECGs printed at 25mm/sec, 1 day before, immediately, 1 day, and 1 month after the revascularization procedure. Myocardial Tl-201 SPECTs were performed before and 1 month after the revascularization and ischemic indices were measured in all cases. RESULTS: Mean QTc dispersion was 51.4+/-17.0msec before revascularization, 42.6+/-15.1msec immediately after, 45.6+/-19.3msec 1 day after and 37.4+/-11.6msec 1 month after revascularization. The decrease of QTc dispersion immediate (p=.001) and 1 month (p<0.001) after revascularization, were statistically significant. Mean Tl-201 SPECT ischemic index measured before the revascularization (7.8+/-5.9) was significantly higher (p<0.001) than the one measured 1 month after the revascularization (1.5+/-2.8). But, in deltaischemic index (ischemic index before revascularization-ischemic index 1 month afer revascularization), there was no significant difference between the patients with decrease in QTc dispersion after revascularization(6.2+/-6.3, n=7) and the patients without decrease in QTc dispersion (6.6+/-5.2, n=). There was no statistically significant correlation between deltaQTc (QTc dispersion before revascularization-QTc dispersion 1 month afer revascularization) and delta ischemic index in total subjects. CONCLUSION: QTc dispersions decrease after successful coronary revascularizations in patients with angina, but considering the relationships between the changes of QTc dispersions and ischemic indices in myocardial dipyridamole Tl-201 SPECT, the degree of decrease in QTc dispersion after coronary revascularization does not have the relationships with the quantitative degree of improvement in myocardial ischemia.