Incremental Value of Left Atrial Geometric Remodeling in Predicting Late Atrial Fibrillation Recurrence After Pulmonary Vein Isolation: A Cardiovascular Magnetic Resonance Study

Abstract

Background Left atrial ( LA ) enlargement is a marker for increased risk of atrial fibrillation ( AF ). However, LA remodeling is a complex process that is poorly understood, and LA geometric remodeling may also be associated with the development of AF . We sought to determine whether LA spherical remodeling or its temporal change predict late AF recurrence after pulmonary vein isolation ( PVI ). Methods and Results Two hundred twenty-seven consecutive patients scheduled for their first PVI for paroxysmal or persistent AF who underwent cardiovascular magnetic resonance before and within 6 months after PVI were retrospectively identified. The LA sphericity index was computed as the ratio of the measured LA maximum volume to the volume of a sphere with maximum LA length diameter. During mean follow-up of 25 months, 88 patients (39%) experienced late recurrence of AF . Multivariable Cox regression analyses identified an increased pre- PVI LA sphericity index as an independent predictor of late AF recurrence (hazard ratio, 1.32; 95% confidence interval, 1.07-1.62, P=0.009). Patients in the highest LA sphericity index tertile were at highest risk of late recurrence (highest versus lowest: 59% versus 28%; P<0.001). The integration of the LA sphericity index to the LA minimum volume index and passive emptying fraction provided important incremental prognostic information for predicting late AF recurrence post PVI (categorical net reclassification improvement, 0.43; 95% confidence interval, 0.16-0.69, P=0.001). Conclusions The assessment of pre- PVI LA geometric remodeling provides incremental prognostic information regarding late AF recurrence and may be useful to identify those for whom PVI has reduced success or for whom more aggressive ablation or medications may be useful.

Keywords: atrial fibrillation; cardiovascular magnetic resonance; late recurrence; left atrial sphericity index; left atrial volume; pulmonary vein isolation.

Figure 1

Measurements of LA maximum volume and sphericity index. Left atrial (LA) maximum volume and sphericity index were measured at the LA end‐diastole frame immediately before the opening of the mitral leaflets using 2‐ and 4‐chamber cine images. LA maximum volume was measured from the area‐length method using atrial length (from the back wall to the line across the hinge points of the mitral valve) and border excluding atrial appendage and pulmonary veins in the 2‐ and 4‐chamber views. The volumetric LA sphericity index was calculated as the ratio of LA maximum volume to the volume of a sphere with maximum LA length diameter among atrial length and transverse length (perpendicular to the atrial length) from the 2‐ and 4‐chamber image. LA length 2ch of 49.3 mm is chosen as the maximum LA length in this case (A). Representative cases with and without increased LA sphericity index (B and C).

Figure 2

Correlation between LA volumetric/geometric remodeling and LA parameters at baseline. A, Changes in LA volume after PVI are mildly negatively correlated with LA volume at baseline (r=−0.30; P<0.001). B, Similar to LA volumetric changes, there was a moderate and negative association between changes in the LA sphericity index after PVI and the LA sphericity index at baseline (r=−0.53; P<0.001). C, Change of LA volume and sphericity index showed no correlation (r=0.11; P=0.11). AF indicates atrial fibrillation; LA, left atrial; PVI, pulmonary vein isolation.

Figure 3

Survival curve for late AF recurrence events after pulmonary vein isolation. Patients with the greatest LA sphericity index (orange line) had the highest recurrence rate during a mean follow‐up of 25 months. Selected P values for comparisons between 2 groups are also shown. AF indicates atrial fibrillation; LA, left atrial.

Figure 4

Association of LA sphericity index to LA maximum volume index and schematic for AF recurrence using LA sphericity and LA maximum volume index. There was a weak correlation between the LA sphericity index and the LA maximum volume index. LA maximum volume index >50.4 mL/m² was determined by receiver operating characteristic curve analysis to predict AF recurrence, while a LA sphericity index of 0.87 showed the highest LA sphericity index tertile. The subgroup with smaller LA maximum volume and higher LA sphericity index (left‐top) had a higher AF recurrence rate compared with the subgroup with a larger LA maximum volume and lower LA sphericity index (right‐bottom) (52% vs 40%). AF indicates atrial fibrillation; LA, left atrial.

Figure 5

Comparison of the ROC curves for late AF recurrence events. Receiver operating characteristic (ROC) curve and corresponding area under the curve (AUC) describing the incremental value of integration of the left atrial (LA) sphericity index (blue line) and the LA passive emptying fraction (passive LAEF) (red line) (A), LA minimum volume index (minimum LAVI) (red line) (B), and combination of passive LAEF and minimum LAVI (red line) (C) to predict late AF recurrence.