title: Manifestation of left atrial events and interatrial frequency gradients in the surface electrocardiogram during atrial fibrillation: contributions from posterior leads.
abstract: BACKGROUND
  In most patients, atrial fibrillation (AF) is initiated and maintained by pulmonary vein foci, but the relationship between left atrial (LA) events and the surface electrocardiogram (ECG) is largely unknown. We investigated whether LA events are reflected in the surface ECG and whether additional information can be obtained from recording posterior leads in patients with AF.
  
  
  RESULTS
  In 10 patients undergoing radiofrequency ablation of AF, we identified 103 5-second segments with a significant frequency gradient between right (RA) and left (LA) intraatrial electrograms, or with frequency changes from segment to segment in the same patient. QRS-T cancellation methods were used to isolate atrial activity in the surface ECG and peak frequencies were computed. Peak frequencies of different posterior leads were very similar (6.0 +/- 1.3 Hz for V10, 6.0 +/- 0.9 Hz for V9, 5.9 +/- 1.4 Hz for V8, 6.0 +/- 1.3 Hz for V7). We found a strong correlation between V1 and RA and between V9 and LA, 0.89 and 0.88, respectively, while the lowest correlation was found between lead V1 and LA, 0.62, P < 0.0001. Magnitude-squared coherence values were highest between V1 and RA and between V9 and LA.
  
  
  CONCLUSIONS
  We have demonstrated that, by recording additional surface ECG leads from posterior locations, RA and LA electrical events and interatrial frequency gradients can be monitored noninvasively.
authors: Northwestern University, Evanston, Illinois 60208-3118, USA.
authors: Simona
authors: S
authors: Petrutiu
authors: Alan V
authors: AV
authors: Sahakian
authors: Westby
authors: W
authors: Fisher
authors: Steven
authors: S
authors: Swiryn
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000175:diagnosis*; D018780:Body Surface Potential Mapping / Q000295:instrumentation* / Q000379:methods*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity