Multiple mechanisms of successful slow-pathway catheter ablation of common atrioventricular nodal re-entrant tachycardia

Abstract

Background: In patients with atrioventricular nodal re-entrant tachycardia, modifications of the antegrade atrioventricular nodal function curve caused by catheter ablation of the so-called slow pathway are heterogeneous, but have not yet been systematically evaluated. Aim: To test the hypothesis that successful treatment is independent of specific electrophysiological modifications of atrioventricular nodal conducting properties. Method: Standard electrophysiological parameters and comparable antegrade atrioventricular nodal function curves were obtained, before and after successful ablation, in 104 patients (mean age 52 ± 16 years; 69 women) affected by the common form of atrioventricular nodal re-entrant tachycardia. Results: Three different major patterns of antegrade atrioventricular nodal function curve were caused by ablation: downward shift of the curve with disappearance of atrioventricular nodal duality, suggesting the elimination of the slow pathway in 54 (52%) patients (type 1); absence of clear modifications of the curve (and of slow pathway ablation) in 33 (32%) patients (type 2); upward shift of the curve, suggesting a further slowing of conduction velocity through the slow pathway in 17 (16%) patients (type 3). Type-1 pattern was more frequent in patients ≤ 45 years, whereas type-2 pattern was more frequent in those > 45 years. Conclusion: Successful ablation of atrioventricular nodal re-entrant tachycardia is independent of specific modifications of antegrade atrioventricular conduction and probably depends on critical nodal and perinodal tissue damage at different sites on the re-entrant circuit. The effects of ablation are influenced by patient age.