title: Time domain analysis of the signal averaged electrocardiogram in patients with a conduction defect or a bundle branch block.
abstract: Doubts have been expressed about the clinical usefulness of time domain analysis of the signal averaged electrocardiogram in patients with prolonged QRS complex duration. We studied 147 patients using a signal averaged ECG (40-250 Hz) whose QRS complex was longer than 100 ms. A baseline electrophysiology study was also performed in 128 of these patients. Seventy-seven patients had a minor (QRS < 120 and > 100 ms) conduction defect. Thirty-seven of these 77 had either induced or spontaneous sustained ventricular tachycardia (group I) and 40 had no sustained ventricular tachycardia (group II). Seventy patients had a major (QRS > or = 120 ms) conduction defect, 44 of whom had sustained ventricular tachycardia (group A). The remaining 26 without this condition formed Group B. Group I compared to group II patients had a longer filtered QRS duration (120.8 +/- 14 vs 104.5 +/- 9.5 ms, P < 0.001), a longer low amplitude signal duration (41 +/- 12.1 vs 31 +/- 12.6 ms, P < 0.0001) and a lower root mean square of the last 40 ms of the filtered QRS complex (27 +/- 29.8 vs 35 +/- 25.3 microV, P = ns). Group A compared to group B had a longer filtered QRS duration (157.7 +/- 20.2 vs 140.7 +/- 15.7 ms, P < 0.001), a longer low amplitude signal duration (57.3 +/- 24.9 vs 37.8 +/- 20.3 ms P < 0.001) and a lower root mean square of the last 40 ms of the filtered QRS complex (14.3 +/- 11.2 vs 22.0 +/- 10.5 microV, P < 0.01). Using conventional late potential criteria, the sensitivity and specificity of the signal averaged ECG for the detection of sustained ventricular tachycardia patients with a minor conduction defect were 89% and 75%, respectively. The same criteria applied to patients with a major conduction defect were sensitive (sensitivity: 87%) but non-specific (specificity: 50%). However, by using modified late potential criteria, such as the presence of two of any of the following three signal averaged parameters: filtered QRS duration > or = 145 ms, low amplitude signal duration > or = 50 ms, root mean square of the last 40 ms of the filtered QRS complex < or = 17.5 microV, we derived a non-optimal but still acceptable combination of sensitivity (68%) and specificity (73%). We conclude that traditional late potential criteria can be applied in patients with a minor conduction defect, but modification of these criteria is necessary to derive useful clinical information for risk stratification of patients with a QRS complex duration > or = 120 ms.
authors.affiliation: Department of Cardiology, Hippokration General Hospital, University of Athens, Greece.
authors.forename: K A
authors.initials: KA
authors.lastname: Gatzoulis
authors.forename: M D
authors.initials: MD
authors.lastname: Carlson
authors.forename: L A
authors.initials: LA
authors.lastname: Biblo
authors.forename: I
authors.initials: I
authors.lastname: Rizos
authors.forename: J
authors.initials: J
authors.lastname: Gialafos
authors.forename: P
authors.initials: P
authors.lastname: Toutouzas
authors.forename: A L
authors.initials: AL
authors.lastname: Waldo
mesh_terms: D000328:Adult; D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D003327:Coronary Disease / Q000175:diagnosis / Q000503:physiopathology; D004562:Electrocardiography / Q000295:instrumentation*; D005260:Female; D005583:Fourier Analysis; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008838:Microcomputers; D008875:Middle Aged; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology; D013997:Time Factors