Predictors of Left Atrial Severe Fibrosis in Patients with Nonvalvular Atrial Fibrillation

Objective The search for predictors of severe (>35 %) left atrial (LA) fibrosis in patients (pts) with nonvalvular atrial fibrillation (AF) directed for catheter ablation (CA).
Materials and Methods 69 pts with nonvalvular AF (57 paroxismal and 12 persistent) aged from 32 to 69 years (mean age 57.1±8.4, 28 females) were included in the study, among them 59 pts (86 %) with arterial hypertension (AH), 24 (34.8 %) – with AH and CAD. Complete physical study, laboratory tests (including NT-proBNP level), comprehensive echocardiography were performed. As a surrogate substrate of LA fibrosis, the area of low-voltage (<0.5 mV) zones in LA was estimated in the process of voltage electroanatomic mapping, as the first stage of CA. The total square of LA fibrosis in absolute values (Sf, cm2) and in percent of total LA square (Sf%), as well as the degree of fibrosis: degree I – <5 %, II – 5–19 %, III – 20–35 %, IV – >35 % were calculated. Degree IV of fibrosis was considered as severe fibrosis.
Results Extent of fibrosis didn’t depend on sex, age, body weight, presence of diabetes, CHA2DS2VASc scores, duration of AF history. There was a tendency to smaller Sf in pts with spontaneous termination of AF compared to those who required cardioversion: 7.2 cm2 (4.4; 17.1) and 12.6 cm2 (4.2; 30.5), respectively (p=0.069). Although NT-proBNP level was normal in 62 % of pts (<125 pg / ml), it was higher in Sf% ≥20 % than in Sf% <5 %: 146.0 (48.0; 276.0) and 42.8 (24.2; 91.0) pg / ml, respectively (p=0.0216). The distribution of pts by left ventricular (LV) geometry types was as follows: normal geometry (t.1) – 34, concentric remodeling (t.2) – 16, concentric LV hypertrophy (t.3) – 8, eccentric LV hypertrophy (t.4) – 11. Compared to pts with t. 1 (reference level), pts with t.3 and t.4 had higher LA volume and LV myocardial mass index, and pts with t.4 had larger end-diastolic LV volume and lower LV ejection fraction. Pts with t.4 tended to have higher Sf% than t.1: 31.1 (10.2; 46.2) and 11.2 (5.1; 28.0), respectively (p=0.053). Using logistic regression 3 independent predictors of LA severe fibrosis were detected: type 4 geometry of LV – OR=8.893 (95 % CI 1.150; 68.78), NT-proBNP >128 pg / ml – OR=6.184 (1.01; 37.99), LA volume index >34 ml / m2 – OR=5.92 (1.05; 33.38). According to ROC analysis, the area of the curve AUC = 0.839 (p<0.001), model specificity – 85.1 %, sensitivity – 70.0 %, predictive accuracy – 82.5 %.
Conclusion In pts with nonvalvular AF predictors of severe (>35 %) LA fibrosis were LV geometry type in the form of eccentric LV hypertrophy, LA volume index >34 ml / m2 and NT-proBNP >128 pg / ml.

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