Exercise-induced QRS prolongation in patients with mild coronary artery disease - Computer analysis of the digitized multilead ECGs

Although exercise-induced QRS prolongation has been reported as a possible marker for inducible ischemia, subtleness of the prolongation makes it unid entifiable from standard, chart-recorded electrocardiograms (ECGs). To over come such a limitation, we measured the QRS width using high-resolution ECG s and examined the diagnostic value of the exercise-induced QRS prolongatio n in patients before and after percutaneous transluminal coronary angioplas ty (PTCA). In 16 patients with single- (n = 12) or double-vessel disease (n = 4), treadmill exercise ECG rests were performed before and after PTCA, w hile continuously recording 8-lead ECGs at 500 Hz. The onset of the QRS com plexes was defined by the earliest deflection, and the end was defined as t he latest deflection among 8 leads with the use of algebraic sum of the abs olute voltage and their time derivatives (dV/dt) from all 8 leads. We compa red QRS complexes before and 1 minute after exercise. Before PTCA, exercise prolonged the QRS width in all but 3 patients (unchanged in 2, decreased i n 1) (84 +/- 7 to 87 +/- 8 ms, P < .005). After PTCA, it decreased in 4, wa s unchanged in 5, and increased in 7 (83 +/- 7 to 83 +/- 6 ms, not signific ant). PTCA shortened postexercise QRS width in all but 3 (unchanged in 2, i ncreased in 1:83 +/- 6 to 87 +/- 8 ms, P < .001). High-resolution ECGs enab led us to measure subtle QRS prolongation induced by mild ischemia. Because the QRS prolongation and ST-segment changes would reflect different aspect s of myocardial ischemia, incorporating this measure into ST segment criter ia might significantly improve the diagnostic accuracy for coronary artery disease.