The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction
Presented in part by Dr. Roberts-Thomson and received first prize in the Heart Rhythm Young Investigators Award Competition at the 29th Annual Scientific Sessions of the Heart Rhythm Society, San Francisco, California, May 14–17, 2008, and published in abstract form (Heart Rhythm 2008;5: S100).
Received 10 February 2009; accepted 6 April 2009. published online 13 April 2009.
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 ± 7mm, 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).
Conclusion
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.
⁎Departments of Cardiology and Cardiothoracic Surgery, Royal Melbourne Hospital, and the University of Melbourne, Melbourne, Australia
†Cardiovascular Research Centre, Department of Cardiology, Royal Adelaide Hospital, and the Discipline of Medicine, University of Adelaide, Adelaide, Australia
Address reprint requests and correspondence: Dr. Jonathan M. Kalman, Department of Cardiology, Royal Melbourne Hospital, Royal Pde. Melbourne 3050, Australia
Drs. Roberts-Thomson and Haqqani are the recipients of Postgraduate Research Scholarships from the National Health and Medical Research Council (NHMRC) of Australia. Dr. Stevenson is the recipient of a Postgraduate Scholarship from the National Heart Foundation of Australia and the Cardiac Society of Australia and New Zealand. Dr. Kistler is the recipient of the Neil Hamilton Fairley Scholarship from the NHMRC of Australia and the National Heart Foundation.
ABSTRACT