title: Late potential analysis: is a mathematically-derived X,Y,Z lead system comparable to a true orthogonal X,Y,Z lead system?
abstract: BACKGROUND
  Analysis of ventricular late potentials (LP) with signal-averaged ECG (SAECG) using three bipolar, orthogonal X,Y, Z leads is a validated method of risk-stratification in patients prone to ventricular tachycardia. The aim of this study was to validate a ECG system, which allows LP analysis using X,Y, Z leads mathematically derived from the standard 12-lead ECG.
  
  
  RESULTS
  In 36 patients (age 56 +/- 12 years, coronary artery disease 71%, LVEF 46 +/- 14%) with known or suspected ventricular tachyarrhythmia, two consecutive SAECGs were recorded, one with mathematically derived and another one with true X,Y, Z leads. Time domain measurements with these different lead systems were compared using linear regression analysis and "Bland-Altman" plots. Correlation was good (r = 0.92) for the filtered QRS complex duration, but poor for the terminal QRS amplitude (RMS) and duration (LAS) criteria (r = 0.66 and 0.61, respectively; P < 0.0001). Defining LPS as present if at least two of the three time domain criteria were abnormal, the result matched in 28 (78%), but differed in 8 (22%) patients.
  
  
  CONCLUSIONS
  SAECG using X,Y, Z leads mathematically derived from the standard 12-lead ECG compared to true bipolar X,Y, Z leads show a close correlation in filtered QRS duration, but can differ considerably in the other time domain measurements, resulting in different interpretation of LP analysis in 22%. Therefore, SAECG registration should currently be performed with true X,Y, Z leads, until the accuracy of other approaches is validated.
authors.affiliation: Division of Cardiology, University Hospital, Petersgraben 4, CH-4031 Basel, Switzerland. tcron@uhbs.ch
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Cron
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zellweger
authors.forename: Peter T
authors.initials: PT
authors.lastname: Buser
authors.forename: Matthias E
authors.initials: ME
authors.lastname: Pfisterer
authors.forename: Stefan
authors.initials: S
authors.lastname: Osswald
mesh_terms: D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000175:diagnosis*; D004562:Electrocardiography; D004566:Electrodes; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology