Outcome predictors of empirical slow pathway modulation: clinical and procedural characteristics and long-term follow-up.

Objective: Catheter-based modulation of the slow pathway is the first-line therapy of atrioventricular nodal reentrant tachycardia (AVNRT), the most common supraventricular tachycardia (SVT). In patients with a typical history, in whom AVNRT is not inducible during an electrophysiological study, the current guidelines allow consideration of empirical slow pathway modulation (ESPM) under the precondition that both, dual nodal pathway physiology (DNPP) and an ECG documentation compatible with AVNRT exist. This recommendation is based on small series. Furthermore, it is unknown whether ESPM is beneficial in the presence of ECG documentation but the absence of DNPP or vice versa in the presence of DNPP but absence of ECG documentation.

Methods: Out of 3003 patients who underwent slow pathway modulation from 1993 to 2013, we included 116 patients (68 female; median age 47.0 years) with symptomatic tachycardia who had non-inducible SVT. All patients either had ECG documentation of SVT (66 %) or DNPP (89 %) or both (54 %). All patients underwent ESPM. No severe complications occurred.

Results: After a follow-up time of 64 ± 5.3 months, 81 % of all patients had benefited from ESPM (49 % freedom of symptoms, 32 % improvement). In patients with ECG documentation but absence of DNPP 100 % benefited (85 % freedom of symptoms; 15 % improvement). In patients with DNPP but absence of ECG documentation 75 % benefited (40 % freedom of symptoms, 35 % improvement).

Conclusion: In a large cohort of patients, ESPM is a safe procedure that improves clinical symptoms in the majority of patients during long-term follow-up. We show for the first time that this also applies for cases where there is no DNPP but a characteristic ECG documentation, and vice versa.