Incremental prevalence of fractionated and inhomogeneous propagation of sinus impulses with increasing atrial depolarization abnormality among outpatients.
BACKGROUND
Prolonged P-wave duration (P-dur) and excessive P-wave dispersion (P-disp) are purported arrhythmogenic substrates for atrial fibrillation. However, the extent of involvement of inhomogeneous, sinus impulse propagation demonstrated by excessive P-disp (> 40 ms) has not been evaluated in relation to increasing P-dur.


METHODS
We appraised our previously studied sample of 500 consecutively numbered, otherwise unselected, electrocardiograms (ECGs) of outpatients from the University of Massachusetts, Worcester, Massachusetts for P-disp, P-dur and P-wave axis (P-axis). P-disp, defined as the difference of the duration between the widest and narrowest P wave, and the greatest P-dur after a 12-lead ECG search, was measured manually to the nearest 10 ms. Normal P-axis was considered 0 to + 75 degrees by manually constructing the mean frontal plane electrical P-axis from the limb leads.


RESULTS
After excluding those with atrial arrhythmias, paced rhythms, errors in lead placement, P waves with low amplitude or overall technically poor tracing, 428 ECGs depicting sinus rhythm formed our final sample. P-dur was strongly associated with P-disp (p<0.0001) but the correlation remained weak (r=0.42). However, when P-dur was divided into 10 ms increments, the prevalence of abnormal P-disp rose incrementally with P-dur, with or without consideration of the P-axis. The prevalence of abnormal P-disp doubled from 30% in those with P-dur of 100 ms to > 60% in those with P-dur of 120 ms. Further, the prevalence exceeded 80% with P-dur of 130 ms and reached 100% with P-dur > 160 ms.


CONCLUSIONS
With increasingly prolonged atrial depolarization, the associated inhomogeneity of sinus impulse propagation across the atria increases. P-dur and P-disp are associated with each other and are consistent with abnormal atrial conduction properties.
Ariyarajah
Vignendra
V
Division of Cardiology, Department of Medicine, St. Boniface General Hospital/University of Manitoba, Winnipeg, Manitoba, Canada. vignendra@hotmail.com
Frisella
Mary E
ME
Spodick
David H
DH
D000553:Ambulatory Care / Q000379:methods*; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D015995:Prevalence; D012849:Sinoatrial Node / Q000502:physiology*; D013997:Time Factors