Evaluating Left Atrial Remodeling And Function With Echocardiography After Radiofrequency Catheter Ablation For Lone Atrial Fibrillation

Background: Left atrial (LA) size and function are of prognostic importance in atrial fibrillation (AF), the widespread condition causing significant morbidity and mortality. Tissue Doppler imaging (TDI) can now be used for the quantitative assessment myocardial movement and deformation, however, its usefulness in evaluating LA function is few reported.Objective: To assess the feasibility of TDI in evaluating atrial function of AF, and to evaluate the impact of catheter ablation on LA morphology and function.Methods: sixty three patients with lone AF and undergone successful catheter RF ablation were enrolled, including 18 patients with sustain AF (SAF group, age 62+/- 7 years) and 45 patients with paroxysmal AF (PAF group, age 61+/- 10 years). Twenty normal subjects (control group, age 58+/- 10 years) were also analyzed. Standard two-dimensional (2-D), pulsed Doppler echocardiograms, and TDI images were performed before,1 month,3 months,6 months and 1 year after the ablation procedure. TDI images were digitally saved during 3 or 5 consecutive cardiac cycles in cine-loop format for off-line analysis. Conventional indices of LA size and systolic function were derived from both 2-D and Doppler modalities, including LA end-systolic anteroposterior, inferosuperior and mediolateral dimensions, the maximal and minimal LA area (LAA) and LA volume (LAV), LAA/LAV pre-P wave, LA active area change fraction and LA active ejection fraction (AAEF), the velocity and velocity-time integral (VTI) of mitral inflow A wave, the velocity ratio and VTI ratio of E/A wave, pulmonary vein A-reversal wave velocity (PV-Ar). To study the LA movement and deformation, TDI, tissue tracking and strain were obtained and analyzed with the region of interest located in the middle part of RA lateral wall, interatrial septum (IAS), and LA lateral walls. The peak systolic, early-diastolic and late-diastolic velocity/strain rate, the total atrial displacement/strain, the active displacement/strain pre-P wave and its percentage of the total displacement/strain were measured. The TDI-derived atrial functional indices were compared between RA, IAS, and LA. The LA size and function were compared between the 3 groups.Results 1) The atrial wall movement and deformation were regular in sinus rhythm, with the velocity and displacement curves similar that of LV, and the strain and strain rate curves reversed to LV. In SAF, the atrial wall movement and deformation were irregular; the curves were out of order. TDI can quantify the atrial wall velocity, displacement, strain and strain rate in most patients. There are some difference in atrial function between different location and some rules were found in normal subjects. The tissue velocity and displacement were higher in annulur level than middle atrial segments, despite the same active displacement percentage. The atrial function as assessed by several TDI-derived indices was quite similar in all left atrium (LA) walls. However, all such indices were higher in the right (RA) than the LA, except the active strain percentage, which were similar between different atrial wall and segments. Compared the relationship between these TDI indices and those expressing atrial mechanical function obtained by the conventional 2-D and pulsed Doppler echocardiography, it was found that the peak systolic strain rate and LA total strain were correlated well with AAEF, while Am,T-P,SR-S and%ε-P were correlated well with transmitral VA, VTI-A, ratio of E/A and VTI-E/A.2) No matter in PAF or in SAF, LA were dilated in lone AF; which were more significant in SAF. Even in lone PAF, the pump function of LA were damaged as compared with control, indicated by decreased active LAA change fraction, AAEF, and PV-Ar, and larger VTI-E/A. TDI revealed decreased LA wall peak systolic velocity and total displacement/strain in SAF. Additionally, LA wall peak systolic and late-diastolic velocities, LA total displacement, the percentage of active displacement/strain were also diminished in PAF, suggesting the abnormality of LA movement and deformation function.3) RF ablation could successfully reserve LA remodeling and improve LA function. The recovery of LA function was more significant and rapid in PAF than in SAF. However, some LA functional indices, such as AAEF, LA peak late-diastolic velocity, and the percentage of active strain remain lower in PAF and SAF than those of control even 1 year after ablation.Conclusion:TDI provides a simple and feasible tool for quantifying atrial function, and it may be potentially useful in clinical management of AF. Dilated LA with damaged movement and deformation function, more severe in SAF, was revealed in apparent "lone" AF. Even in PAF, the residual LA function abnormality may last more than 1 year after a successful RF ablation, in despite of the rapid reversion of LA remodeling and significant improvement of LA function, implicating the necessity of long-term clinical treatment and follow-up.