title: Role of the low amplitude potential in the initial P wave signal-averaged electrocardiogram [corrected] in sick sinus syndrome.
abstract: BACKGROUND
  The cause of abnormally low amplitude of the initial P wave signal-averaged electrocardiogram (P-SAECG) in patients with sick sinus syndrome (SSS) is unknown.
  
  
  RESULTS
  Thirteen normal patients (Group C) and 33 with SSS (Group S) were examined. The root mean square amplitude for the initial 30 ms (EP30) and the duration of below-4 microV signals of the filtered P waves (ED4) were measured using the P-SAECG. The interval from an atrial potential on the sinus-node electrogram (SNE) to P wave onset (AS-P), and the interval from the P wave to the atrial potential on the His-bundle-electrogram (P-AH) were measured in the electrophysiological study. The sino-atrial conduction time was measured by a conventional method (indirect sino-atrial conduction time (SACTi)) and using SNE (direct sino-atrial conduction time (SACTd)). The EP30 was significantly lower and the ED4 significantly longer in Group S. The AS-P was significantly longer in Group S (p<0.01), but the P-AH was not different. In Group S, the AS-P was significantly correlated with EP30 and ED4 (p<0.01), but the P-AH was uncorrelated. The SACTi was significantly correlated with EP30 and ED4 (p<0.05), but the SACTd was uncorrelated.
  
  
  CONCLUSIONS
  The abnormality of the initial portion of the P-SAECG observed in SSS appears to be due to disturbed conduction through the atrial myocardium around the sino-atrial node.
authors.affiliation: Division of Cardiovascular Medicine, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Hidehito
authors.initials: H
authors.lastname: Takase
authors.forename: Shinobu
authors.initials: S
authors.lastname: Imai
authors.forename: Fumio
authors.initials: F
authors.lastname: Saito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yagi
authors.forename: Toshio
authors.initials: T
authors.lastname: Kushiro
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001146:Arrhythmia, Sinus / Q000503:physiopathology; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012804:Sick Sinus Syndrome / Q000503:physiopathology*; D012849:Sinoatrial Node / Q000503:physiopathology*