title: A potential pitfall of the modified 12 lead electrocardiogram (Mason-Likar modification) in catheter ablation of idiopathic ventricular arrhythmias originating from the outflow tract.
abstract: OBJECTIVE
  The Mason-Likar modified electrocardiogram (ML-ECG) can be interchanged with standard 12 lead ECG electrode positions (standard ECG) without affecting the diagnostic interpretation during sinus rhythm, but the morphological differences during ventricular arrhythmias have not been sufficiently evaluated. This study aimed to elucidate the morphological changes in the ML-ECG precordial leads.
  
  
  RESULTS
  In 53 consecutive patients with premature ventricular contractions predicted to originate from the outflow tract (OT-PVCs), the arrhythmias were analysed by those two ECG methods. The OT-PVC origin sites, which were predicted by currently published criteria with the respective ECG methods prior to catheter ablation, were compared with the successful ablation sites. Compared with the standard-ECG, S-waves in the ML-ECG became shallower in leads V1-4 (P < 0.05 in lead V1; P < 0.001 in leads V2-4), and pseudo-R-waves in lead V1 appeared in seven patients. The precordial leads transition zone shifted counter-clockwise in 18 patients in the ML-ECG. In leads I and aVL, the negative deflection amplitudes of the ML-ECG were greater than those of the standard ECG (P < 0.001), and polarity reversals in lead I appeared in 18 patients. The R-wave amplitudes in all ML-ECG inferior leads were greater than those in the standard-ECG leads (all for P < 0.001). Those changes had an effect on the diagnostic indexes for the localization, and the specificity of the criteria for the ML-ECG was poorer than that for the standard-ECG.
  
  
  CONCLUSIONS
  Great differences were found between those two ECG methods. Predicting OT-PVC origins by diagnostic criteria with the ML-ECG might result in a misdiagnosis and inefficient ablation.
authors.affiliation: Department of Cardiology, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan su9uru@me.com.
authors.forename: Suguru
authors.initials: S
authors.lastname: Nishiuchi
authors.affiliation: Department of Cardiovascular Medicine, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Fukui, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kaseno
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Shigeto
authors.initials: S
authors.lastname: Naito
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Tsukada
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Takehito
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Department of Cardiology, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Hayano
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Keijiro
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Sato
authors.affiliation: Department of Cardiovascular Medicine, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Fukui, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Ikeda
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Miki
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Kohki
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kumagai
authors.affiliation: Department of Cardiology, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Oshima
authors.affiliation: Department of Cardiovascular Medicine, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Fukui, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tada
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D017115:Catheter Ablation; D003951:Diagnostic Errors; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology / Q000601:surgery*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D018879:Ventricular Premature Complexes / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*
keywords: Catheter ablation; Electrocardiogram; Idiopathic ventricular arrhythmia; Mason–Likar; Modification; Outflow tachycardia