Introduction: Atrioventricular nodal reentry tachycardia (AVNRT) is the most common paroxysmal supraventricular tachycardia (SVT). Slow pathway modulation (SPM) is the accepted first line treatment with reported success rates of SPM ranging around 95%. Information regarding AVNRT recurrences and possible predictors following a primarily successful procedure is very limited.

Methods and Results: Out of 4170 consecutive patients with SPM in our department from 1993-2017, we retrospectively identified 51 (1,2%) patients receiving >1 SPM (35 female (69%), average age at first SPM 51±15 years) with a clinical recurrence of AVNRT after an initially successful first SPM. We matched these patients for age, gender and number of radiofrequency (RF) ablation impulses during first SPM with 51 patients who received one successful SPM in our center without AVNRT recurrence. Both groups were contacted for a telephone questionnaire and analyzed for possible predictors of a recurrence of AVNRT. In the group of patients having had a clinical recurrence of AVNRT, 39 patients (76,5%) had a SVT ECG documentation before the first SPM. In 32 patients (62,7%), the AVNRT could be induced without the administration of orciprenaline. 4 patients (7,8%) exhibited an atypical AVNRT. In 11 patients (21,6%) at least one additional SVT (7 EAT, 8 atrial fibrillation/flutter) was induced during EPS. During SPM, a median of 5,5 RF impulses were applied (interquartile range: 2-12) with a maximum of 50 watts and 60°C. In 11 patients (21,6%), SPM resulted in a complete absence of dual atrioventricular nodal pathway physiology (DNPP). No major complications occurred in both groups. 

In the group with AVNRT recurrence, the majority of patients had no change in symptoms after the first successful ablation. Regarding possible predictors of recurrence, there were no significant differences in intraprocedural parameters (length of RF impulses (3 vs 2 min; p=0,15), length of EPS (105 vs 98 min; p=0,56), fluoroscopy time (603 vs 556 seconds; p=0,17), radiation dose (230 vs 294 cGy*cm2; p=0,24), inducibility of AVNRT (49 vs 47 patients; p=0,68), induction of AVNRT without orciprenalin (32 vs 25 patients, p=0,23), atypical AVNRT (4 vs 2 patients, p=0,68), induction of other SVT (11 vs 7, p=0,44), occurrence of junctional beats during ablation (34 vs 42 patients, p=0,11), presence of DNPP after SPM (40 vs 33 patients, p=0,19)) or cardiovascular comorbidities (hypertension (20 vs 17 patients, p=0,68), heart failure (1 vs 2 patients, p=0,56)). There was, however, a significantly higher number of patients with previously diagnosed other SVT (10 [5 atrial fibrillation, 5 ectopic atrial tachycardia] vs. 2 patients, p=0,014) and diabetes (10 vs. 3 patients, p=0,036) in the group with AVNRT recurrence. All patients in both groups reported an absence of symptoms or substantial improvement in symptoms after the last SPM.

Conclusion: In a small percentage AVNRT recurs after an initially successful ablation. Interestingly, these patients were not different regarding procedural characteristics as a potential measure of difficulty in achieving SPM. Patients with an AVNRT recurrence were, however, more likely to have previously known other arrhythmias and diabetes.