Cardioneuroablation in Cardioinhibitory Vasovagal Syncope: Insights From Iodine-123 Metaiodobenzylguanidine Imaging and Heart Rate Variability

Background Cardioneuroablation is used in selected patients with cardioinhibitory vasovagal syncope, but its effects on myocardial sympathetic imaging parameters remain incompletely defined. Objective To evaluate changes in iodine-123 metaiodobenzylguanidine-derived myocardial sympathetic imaging parameters and heart rate variability after cardioneuroablation. Methods This prospective, single-arm, pre-post observational study included 15 consecutive patients with head-up tilt test-proven type 2B cardioinhibitory vasovagal syncope who underwent clinically indicated cardioneuroablation. Twenty-four-hour Holter monitoring and iodine-123 metaiodobenzylguanidine scintigraphy were performed before and 1 month after the procedure. The primary outcome was change in delayed heart-to-mediastinum ratio. Secondary analyses were adjusted using the Benjamini-Hochberg false discovery rate procedure. Results Mean age was 31.9 (9.0) years, and 4 patients (26.7%) were male. Delayed heart-to-mediastinum ratio increased from 2.014 (0.273) to 2.137 (0.233), with a mean paired increase of 0.123 (95% bootstrap CI, 0.049-0.169; Wilcoxon P=.007). Mean heart rate increased and RMSSD decreased after cardioneuroablation; both remained significant after false discovery rate adjustment. Change in delayed heart-to-mediastinum ratio correlated inversely with percentage change in RMSSD (Spearman ρ = -0.789; FDR-adjusted P=.004). No patient experienced syncope or presyncope during the 1-month follow-up. Conclusion Cardioneuroablation was associated with a modest increase in delayed heart-to-mediastinum ratio and reductions in vagally mediated heart rate variability indices at 1 month. These exploratory findings are consistent with postprocedural autonomic remodeling and require confirmation in larger controlled studies.