Poor relationship between left atrial diameter and volume in patients with atrial fibrillation

Abstract

BackgroundLeft atrial (LA) enlargement is a predictor of worse outcome after catheter ablation for atrial fibrillation (AF). We investigated the correspondence between single LA diameter (LAd) and LA volume (LAV) in patients undergoing catheter ablation for AF. MethodsTotal 782 patients (aged 58±11 yrs; 70% males; 56% paroxysmal AF) were enroled in 2 centres in the period of 2007–2011. Echocardiographic antero-posterior LAd was assessed in parasternal long-axis view and LAV was derived from electroanatomic 3D reconstruction of LA (183±50 CARTO mapping points; 55% CT image registration). ResultsMean LAd was 45±6mm (median: 45; IQR: 41–49; range: 25–73mm) and mean LAV was 134±42ml (median: 128; IQR: 103–160; range: 46–313ml). Correlation between both variables was weak (r=0.56; p <0.0001) and area under the ROC curve for the LAd-based prediction of LAV >130 was 0.76. Accordingly, severe dilation of LA (LAV >160ml; upper quartile) was found only in 56% of patients with LAd >50mm while it appeared in 11% of those with LAd<45mm. In multivariate regression analysis, age, gender, and type of AF were independent covariates of LAV yielding the equation of LAV (ml)=68+0.41.cube LAd (cc)+15 (if male)+0.48.age (yrs) – 21 (if paroxysmal AF). Substantial between-centre bias was also found reflecting subjective nature of echocardiographic readings. Adjustment for all covariates improved the correspondence between LAd-predicted and true LAV only modestly (AUC increased from 0.76 to 0.83) with wide 95% limits of agreement (−58 to +60ml). ConclusionsConsiderable disagreement between echocardiographic LAd and 3D mapping LAV was observed in patients with non-valvular atrial fibrillation. Single LA dimension should not be considered relevant criterion for the indication of rhythm/rate control therapy and, particularly, for the selection of suitable candidates for catheter ablation.