title: Exercise-induced QRS prolongation in patients with mild coronary artery disease: computer analysis of the digitized multilead ECGs.
abstract: Although exercise-induced QRS prolongation has been reported as a possible marker for inducible ischemia, subtleness of the prolongation makes it unidentifiable from standard, chart-recorded electrocardiograms (ECGs). To overcome such a limitation, we measured the QRS width using high-resolution ECGs and examined the diagnostic value of the exercise-induced QRS prolongation in patients before and after percutaneous transluminal coronary angioplasty (PTCA). In 16 patients with single- (n = 12) or double-vessel disease (n = 4), treadmill exercise ECG tests were performed before and after PTCA, while continuously recording 8-lead ECGs at 500 Hz. The onset of the QRS complexes was defined by the earliest deflection, and the end was defined as the latest deflection among 8 leads with the use of algebraic sum of the absolute voltage and their time derivatives (dV/dt) from all 8 leads. We compared QRS complexes before and 1 minute after exercise. Before PTCA, exercise prolonged the QRS width in all but 3 patients (unchanged in 2, decreased in 1) (84 +/- 7 to 87 +/- 8 ms, P < .005). After PTCA, it decreased in 4, was unchanged in 5, and increased in 7 (83 +/- 7 to 83 +/- 6 ms, not significant). PTCA shortened postexercise QRS width in all but 3 (unchanged in 2, increased in 1: 83 +/- 6 to 87 +/- 8 ms, P < .001). High-resolution ECGs enabled us to measure subtle QRS prolongation induced by mild ischemia. Because the QRS prolongation and ST-segment changes would reflect different aspects of myocardial ischemia, incorporating this measure into ST segment criteria might significantly improve the diagnostic accuracy for coronary artery disease.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Suita, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takaki
authors.forename: N
authors.initials: N
authors.lastname: Tahara
authors.forename: S
authors.initials: S
authors.lastname: Miyazaki
authors.forename: M
authors.initials: M
authors.lastname: Sugimachi
authors.forename: K
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000328:Adult; D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D003327:Coronary Disease / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D016896:Treatment Outcome