ISMICS 2006 Annual Meeting Poster Session: Session 6 – Innovative Techniques and Technologies II
The Cox-Maze procedure remains the gold standard for the surgical treatment of atrial fibrillation. Although the procedure has excellent long-term results, its effect on atrial function has not been well-characterized. The objective of this study was to non-invasively characterize normal porcine left atrial (LA) function, and to evaluate the effect of the Cox-Maze procedure on LA function in a chronic animal model using cardiac magnetic resonance imaging (MRI).
Cardiac MRI data was obtained from 10 healthy pigs to define normal LA function. In addition, postoperative cardiac MRI (at 30 days) was obtained in 6/10 pigs that underwent a modified Cox-Maze procedure using either bipolar radiofrequency ablation or cryoablation energy sources. A clinical 1.5 Tesla MRI scanner was used to obtain multiple anatomical/functional cine images. Atrial volume vs. cardiac cycle curves were derived by calculating the atrial volume in each phase of the cardiac cycle. Left atrial volume at each point of the cardiac cycle was calculated by adding the surface area of each short axis stack image of the left atrium using Simpson’s rule. LA passive filling and emptying was derived from the total emptying fraction. Active contractility function was derived from the active atrial ejection fraction. The total emptying fraction was calculated using the absolute maximum and minimum LA volumes; the active atrial ejection fraction (atrial kick) was calculated using pre-atrial contraction relative maximum and absolute minimum LA volumes.
The mean total LA emptying fraction and the mean active LA ejection fraction was 32.2±6.3% (n=10) and 18.9±1.1% (n=3), respectively, in normal pigs. Six pigs that underwent the modified Cox-Maze procedure had preoperative mean total LA emptying fraction of 31.2±7.1%, which decreased to 23.3±3.1% postoperatively (p=0.03).
The Cox-Maze procedure decreases left atrial function in normal porcine atria. The total LA emptying fraction was decreased postoperatively following the modified Cox-Maze procedure.