The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction.
BACKGROUND
The posterior left atrium (LA) is involved in the initiation and maintenance of atrial fibrillation (AF).


OBJECTIVE
The purpose of this study was to compare conduction patterns on the posterior LA in patients with mitral regurgitation (MR), with and without AF.


METHODS
Epicardial mapping of the posterior LA was performed in 23 patients undergoing cardiac surgery. Patients were included in one of three groups: Group A-patients in sinus rhythm with normal left ventricular function undergoing coronary artery bypass grafting, Group B-patients in sinus rhythm with MR undergoing mitral valve surgery, or Group C-patients in persistent AF with MR undergoing mitral valve surgery. Conduction patterns, regional conduction velocity, conduction heterogeneity, conduction anisotropy, and complex fractionated atrial electrograms (CFAEs) were assessed.


RESULTS
LA diameter was greater in patients in Groups C (57 +/- 4mm) and B (54 +/- 6mm) than in Group A (39 +/- 7 mm, P <0.01). Patients in Group C had a greater number of lines of conduction delay than Groups A and B (2.0 +/- 0.8 vs 1 +/- 0 and 1 +/- 0, P <0.05). The extent of conduction delay and conduction heterogeneity was greater in Group C than in Group B, which was greater than in Group A (P <0.05). The percentage of CFAEs that remained stable during AF was 61% +/- 17%. There was a significant correlation between CFAEs during AF and regions of slow conduction during pacing (R = 0.36, P <0.001).


CONCLUSIONS
Patients with MR, LA enlargement, and AF have more extensive regions of conduction slowing in the posterior LA. Anatomically constant lines of conduction delay in this region lead to circuitous wavefront propagation. During persistent AF, fractionated electrograms in the posterior LA are distributed to regions demonstrating slow conduction, and the majority remain stable over time.
Roberts-Thomson
Kurt C
KC
Department of Cardiology and Cardiothoracic Surgery, Royal Melbourne Hospital, University of Melbourne, Melbourne, Australia.
Stevenson
Irene
I
Kistler
Peter M
PM
Haqqani
Haris M
HM
Spence
Steven J
SJ
Goldblatt
John C
JC
Sanders
Prashanthan
P
Kalman
Jonathan M
JM
D000368:Aged; D001281:Atrial Fibrillation / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D002304:Cardiac Pacing, Artificial; D006348:Cardiac Surgical Procedures; D016022:Case-Control Studies; D002908:Chronic Disease; D001026:Coronary Artery Bypass; D005260:Female; D006325:Heart Atria / Q000503:physiopathology* / Q000601:surgery; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008944:Mitral Valve Insufficiency / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D013223:Statistics as Topic; D013997:Time Factors