Myocardial morphological changes and pulmonary vein catheter ablation efficacy in patients with atrial fibrillation

Aim. To study the association between morphological changes and comorbidities and atrial fibrillation (AF) catheter ablation efficacy, and to evaluate morphological predictors of AF recurrence in patients with durable pulmonary vein isolation (PVI) after catheter intervention.

Material and methods. Fifty-four patients with paroxysmal/persistent AF without severe structural heart disease were enrolled in this study who underwent primary pulmonary vein cryoballoon ablation (CBA) with simultaneous implantation of an electrocardiogram loop recorder (Medtronic Reveal XT) and interatrial/interventricular septum biopsy. The follow-up duration was 12 months with scheduled 3, 6 and 12 month visits. Patients with recurrent AF were referred for redo procedure, where the PVI durability was assessed. The follow-up duration after the second procedure was also 12 months. The patients were divided into two groups: patients without recurrent AF and patients with recurrent AF after two catheter interventions.

Results. In interventricular septum biopsy samples we found the morphological criteria of myocarditis in 70% of the patients (n=34). Individual morphological changes were detected in all patients. The most common types were cardiomyocyte hypertrophy — 98,1% (n= 52), overcrossing of cardiomyocytes — 77,4% (n=41) and lymphohistiocytic infiltration of the interstitium by more than 14 cells — 75,5% (n=40). Patients with persistent AF were significantly more likely to have endothelial cell swelling (55% vs 45%, p=0,022). Interstitial tissue edema was the only morphological parameter significantly associated with AF recurrence (p=0,03).

Conclusion. In patients with AF and no structural heart disease who underwent drug-resistant AF cryoballoon ablation, morphological changes in the myocardium of the atria and ventricles are detected in 100% of cases. The predominant biopsy diagnosis is myocarditis. Morphological signs of the inflammatory process activity, as interstitial tissue edema are associated with the high incidence of non-venous AF. Further preoperative evaluation is needed to identify patients with non-venous atrial fibrillation, which will increase the effectiveness of interventional approach.

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