Evaluation of short-term and long-term results of cardioneuromodulation procedure in patients presenting with syncope

Vasovagal syncope commonly affects young individuals. In recent years, the endocardial ablation of cardiac parasympathetic ganglion plexi, termed "cardioneuromodulation (CNM)," has emerged as a novel therapeutic approach. This study aims to evaluate the efficacy and safety of CNM in patients presenting with syncope. Fifty-seven patients who presented with syncope to the Hacettepe University Cardiology Clinic and underwent KNM between October 2019 and August 2023 were included. All patients had a positive cardioinhibitory tilt table test. Pre- and post-procedural rhythm Holter recordings were examined. Intracardiac electrogram (EGM) measurements and standard electrophysiological study parameters during and after the procedure were analyzed to determine the endpoints and efficacy of KNM. Symptoms and complications were assessed for three times during 1 year follow-up (0-4 months, 5-8 months, and 9-12 months). The mean number of syncopal episodes was 2.68±1.58 before the procedure and 0.28±0.56 at the one-year follow-up (Z=-6.359, p<0.001). During follow-up, 14 patients (24.5%) experienced a syncope episode. Syncope was reported by 2 patients (3.5%) at the first follow-up, 7 patients (12.3%) at the second follow-up, and 10 patients (17.5%) at the third follow-up. The post-procedural P-P interval reduction percentage and heart rate increase percentage values were significantly higher in the non-recurrent group compared to the group with recurrence (p<0.05). Subgroup analyses were conducted by dividing the patient population into three groups: those with recurrence, those without recurrence and any complaints, and those without recurrence but with palpitations. Specifically, the percentage reduction in P-P intervals was 21.9%, 23.2%, and 26.5% (F=4.086; p=0.022) and the percentage increase in heart rate was 23.9%, 32.1%, and 38.8% (F=3.971; p=0.025) in the recurrence, non-recurrence and complaint, and non-recurrence with palpitations groups, respectively. Procedural data indicated that the number of ablation lesions (F=7.125; p=0.002), average impedance drop (F=4.184; p=0.020), lesion area (χ2=11.028; p=0.004), and RF duration (F=3.343; p=0.043) were significantly higher in the non-recurrence but palpitations group compared to the other two groups. The study results indicate that KNM substantially reduces the number of syncopal episodes at one-year follow-up. Based on our findings, targeting a P-P interval increase percentage between 23% and 26.5% and a heart rate increase percentage between 32.2% and 38.8% may provide a safe zone to prevent both syncope recurrence and palpitations. However, large-scale, prospective, randomized studies are needed to identify all factors affecting procedural success and syncope recurrence, establish a standard ablation endpoint for adequate vagal denervation, and incorporate these findings into routine clinical practice.