Time course of left atrial mechanical recovery after linear lesions: Normal sinus rhythm versus a chronic atrial fibrillation dog model

Introduction: The extent of left atrial (LA) mechanical function recovery after creation of linear lesions using the loop catheter has not been determined. Methods and Results: LA mechanical function was assessed before and after linear lesions using transthoracic two-dimensional and Doppler echocardiography in two groups: (1) normal, which consisted of eight healthy dogs in normal sinus rhythm (NSR); and (2) atrial fibrillation (AF), which consisted of nine dogs in spontaneous AF for 6 months following rapid pacing-induced AF. NSR was restored with linear lesions in all AF dogs. All animals were in NSR 5 months after linear lesions. In the normal dogs, the maximal. velocity of the transmitral flow "A" wave was reduced by 42% during the first week postablation and by 24% at 5 months versus preablation. At 5 months, no differences in LA function were noted between the normal and the AF group for all measured Doppler parameters. At 5 months, the LA systolic area in AF dogs was reduced by 40% (preablation 12.9 +/- 2.9 cm(2) postablation 7.6 +/- 1.2 cm(2); P < 0.01) and in the normal dogs by 21% (preablation 10.0 +/- 0.9 cm(2), postablation 7.8 +/- 1.2 cm(2); P < 0.02), being the same in both groups within 3 months of recovery. Conclusion: The creation of linear lesions with the loop catheter does not result in LA expansion. In normal dogs, LA mechanical activity is reduced for 3 weeks postablation. The time course of LA mechanical function recovery is the same for the AF and the NSR dogs, and it is complete at 3 months postablation. At 5 months, LA systolic function parameters in both groups are reduced by 24% versus the preablation values of the normal dogs. Linear lesions result in a significant reduction in LA size.