[Serial changes in QT interval during the course of acute ischemic episode: with special reference to intracoronary...

The change in electrocardiogram (ECG) during percutaneous transluminal coronary angioplasty (PTCA) was investigated by recording both standard 12 lead ECG (surface ECG) and intracoronary electrogram (ic-ECG) before, during and after PTCA with right atrium pacing (80/min). During the ischemia induced by PTCA, the amplitude of QRS complex revealed an initial decrease in amplitude and later increase in ic-ECG, however, it only showed an initial decrease in surface ECG up to 5 minutes, while the QRS interval showed a significant decrease in only in ic-ECG (77 +/- 14 vs 75 +/- 13 msec). The QT interval became shorter with the increase in the duration of ischemia, the difference being statistically significant even for the initial 20 seconds of ischemia in both ic-ECG (398 +/- 27 vs 370 +/- 22) and surface ECG. In the case of acute myocardial infarction, the direction of T wave and QT interval seemed to depend on the degree of reperfusion. Hence, in patients who underwent successful reperfusion therapy the QT interval was lengthened initially and later shortened, cardiac function preserved and T wave normalized in anteroseptal myocardial infarction, while in those who had unsuccessful reperfusion the QT interval was progressively lengthened, cardiac function was not preserved well and T wave was not normalized. Therefore, in patients with a positive T wave the QT interval was shorter (382.4 +/- 42.6 vs 448.7 +/- 29.7 msec), with better fractional shortening (4.24 +/- 2.2 vs 1.95 +/- 1.2) and better left ventricular ejection fraction (68.1 +/- 6.1 vs 52.9 +/- 14.7%) than in the patients with negative T wave in lead V2 in the chronic stage.(ABSTRACT TRUNCATED AT 250 WORDS)