title: Biphasic P wave in inferior leads and the development of atrial fibrillation.
abstract: BACKGROUND
  Anisotropic and slow conduction in the atrium underlie the development of atrial fibrillation (AF). This study aimed to investigate the P wave characteristics associated with the development of AF in patients with a biphasic P wave in the inferior leads.
  
  
  METHODS
  Digital analysis of retrospectively recorded 12-lead electrocardiograms was performed to select patients with a biphasic P wave (positive/negative) in lead II from a database of 114,334 patients. Characteristics of the P wave in the inferior leads associated with incidence of AF were determined. Receiver operating characteristic curves dichotomized P wave variables were measured in each lead.
  
  
  RESULTS
  A total of 141 patients (77 men; mean age, 64±19 years) were enrolled in this study. Twenty-nine (20.6%) patients developed AF (AF group) vs. 112 (79.6%) who did not (non-AF group) during a follow-up period of 50±62 months. The amplitude of the initial P wave portion in lead II was significantly larger in the AF group when compared with the non-AF group (77.3±77.0 µV vs. 51.0±30.1 µV, p=0.003), while the amplitude of the terminal P wave portion in lead III was significantly decreased in the AF group when compared with the non-AF group (-70.6±41.3 µV vs. -89.1±38.1 µV, p=0.024). The duration of the initial P wave portion in lead III was significantly longer in the AF group when compared with the non-AF group (52.7±34.6 ms vs. 35.8±30.4 ms, p=0.011). Multivariate Cox proportional-hazards analysis confirmed that the increased duration of the initial P wave portion in lead III (≥71 ms) was independently associated with AF development (hazard ratio 2.90, 95% confidence interval 1.16-7.11, p=0.02).
  
  
  CONCLUSIONS
  The analyses of the biphasic P wave in the inferior leads suggest that the development of AF could be attributed to increased atrial slow conduction.
authors.affiliation: Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.affiliation: Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Horie
keywords: Atrial fibrillation; Biphasic P wave; Conduction; Electrocardiography; Prognosis