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

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 < or = 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.