An interventional study of Focal Cryoablation and Radiofrequency Catheter Ablation in Bradycardia, Syncope, Vasovagal and Sick Sinus Syndrome, sponsored by Tomsk National Research Medical Center of the Russian Academy of Sciences. Recruiting at 1 site in Russia. Open to participants aged 18 Years to 60 Years. Per ClinicalTrials.gov, last updated 2026-06-26.
Sponsored by Tomsk National Research Medical Center of the Russian Academy of Sciences · Not applicable, Interventional, and Treatment
Bradyarrhythmias are conditions where the heart beats too slowly, causing symptoms like dizziness, fainting, and fatigue. In some patients, these slow heart rhythms are caused by overactivity of the vagus nerve (the part of the nervous system that slows the heart down).
Cardioneuroablation (CNA) is a catheter-based procedure that targets and reduces the effect of these overactive nerves on the heart. It is an alternative to permanent pacemaker implantation, especially for younger patients.
Traditionally, CNA is performed using radiofrequency (RF) energy to create small burns in specific areas of the heart. This study investigates whether focal cryoablation (freezing technology using the Freezor™ Xtra catheter) is as safe and effective as standard RF ablation for CNA.
This is a prospective, non-randomized study. Participants will receive either RF ablation (N=30) or cryoablation (N=30). The study will evaluate the recurrence of slow heart rhythms and fainting episodes, as well as any complications, over 12 months of follow-up.
Background and Rationale
Cardioneuroablation is an emerging treatment for vagally-mediated bradyarrhythmias, including symptomatic sinus bradycardia, atrioventricular blocks, and vasovagal syncope with a cardioinhibitory component . The procedure targets ganglionated plexi located in the epicardial fat and myocardium, which contain parasympathetic nerve endings.
While radiofrequency (RF) energy is the standard modality for CNA, epicardial fat may limit RF lesion formation when fat thickness exceeds 3 mm. Cryoablation, by contrast, uniformly cools tissue without energy dissipation in fat, potentially offering more consistent ganglion ablation.
To date, no clinical study has compared focal cryoablation versus RF ablation specifically for cardioneuroablation.
Objectives
Primary: To compare the efficacy of focal cryoablation versus RF ablation for cardioneuroablation in preventing bradyarrhythmia recurrence.
Secondary: To compare the safety profile of both techniques, including periprocedural complications and inappropriate sinus tachycardia.
Study Design
This is a prospective, non-randomized, parallel-group study conducted at a single center (Cardiology Research Institute, Tomsk NRMC). Eligible patients aged 18-60 years with symptomatic vagally-mediated bradyarrhythmias (confirmed by positive atropine test and/or EP study) are assigned non-randomly to either:
Group 1 (RF-CNA, N=30): Radiofrequency ablation using TactiFlex™ SE catheter (Abbott), power 45W, target AI 45, with irrigation
Group 2 (Cryo-CNA, N=30): Focal cryoablation using Freezor™ Xtra 6mm catheter (Medtronic), target temperature -75°C, 240 seconds per application
Procedures
All procedures are performed under intravenous sedation. After establishing venous access, a 3D electroanatomical map of the right atrium is created using the EnSite™ X system with HD Grid mapping catheter. Ganglionated plexi are identified using spectral analysis (OTNF algorithm) and anatomical landmarks (RAGP and IRGP).
Ablation is applied at identified sites. Intraprocedural endpoints include:
Reduction of SNRT \<1500 ms and cSNRT \<525 ms
Wenckebach point ≥140 bpm
AV node ERP >300 ms
Absence of bradycardic response to phenylephrine (\<10% heart rate reduction)
Follow-up
Patients are followed at 6 and 12 months post-procedure with clinical assessment, 12-lead ECG, and 24-hour Holter monitoring.
Statistical Considerations
The planned sample size is 60 patients (30 per group). Quantitative variables will be presented as mean±SD or median [Q1;Q3]. Paired t-test or Wilcoxon test will be used for pre-post comparisons. Between-group comparisons will use Mann-Whitney U test. Statistical significance set at p\<0.05.
317 studies on the registry are indexed under Bradycardia; 71 are open to participants now.
This study's planned enrollment of 60 is below the median of 100 across 187 interventional studies indexed under Bradycardia.
Browse Bradycardia studies →Tomsk National Research Medical Center of the Russian Academy of Sciences is the lead sponsor of 73 studies on the registry; 19 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A “mini-stroke”: temporary stroke-like symptoms caused by reduced blood flow to part of the brain, spinal cord or eye, without signs of a new stroke on a scan.
Stroke symptoms need emergency care at once, even if they go away.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
TIA (transient ischaemic attack)
A “mini-stroke”: temporary stroke-like symptoms caused by reduced blood flow to part of the brain, spinal cord or eye, without signs of a new stroke on a scan.
Stroke symptoms need emergency care at once, even if they go away.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Procedure: Focal Cryoablation
Procedure: Radiofrequency Catheter Ablation
Focal cryoablation of right atrial ganglionated plexi using Freezor™ Xtra 6mm catheter (Medtronic) at -75°C for 240 seconds per application. 3-5 applications per GP zone. Positioned by fluoroscopy and impedance-based tracking in EnSite™ X system.
Radiofrequency ablation of right atrial ganglionated plexi using TactiFlex™ SE catheter (Abbott) with power up to 45W, temperature 50°C, target AI 45, with irrigation. 3-5 applications per GP zone. Guided by EnSite™ X mapping system and spectral analysis (OTNF).
Recurrence of Bradyarrhythmia or Syncope
Documented recurrence of symptomatic bradyarrhythmia (sinus bradycardia \<40 bpm, pause \>3 sec, AV block) or syncope confirmed by ECG or Holter
Time frame: 12 months
Pericardial Effusion or Hemopericardium
Pericardial effusion or hemopericardium requiring intervention, confirmed by echocardiography
Time frame: Periprocedural (7 days)
Inappropriate Sinus Tachycardia
Sustained sinus tachycardia \>100 bpm without cause, requiring beta-blocker therapy
Time frame: 12 months
Vascular Access Complications
Hematoma, pseudoaneurysm, or AV fistula requiring treatment, confirmed by ultrasound
Time frame: Periprocedural (7 days)
Change in Minimum Heart Rate
Absolute change in minimum heart rate (bpm) on 24-hour Holter from baseline to 6 months
Time frame: Baseline to 6 months
Change in Maximum Heart Rate
Absolute change in maximum heart rate (bpm) on 24-hour Holter from baseline to 6 months
Time frame: Baseline to 6 months
Change in Electrophysiological Parameters
Normalization of cSNRT \<525 ms, Wenckebach point ≥140 bpm, AV-ERP \>300 ms
Time frame: Intraprocedural
Change in Mean Heart Rate
Absolute change in minimum heart rate (bpm) on 24-hour Holter from baseline to 6 months
Time frame: Baseline to 6 months
Plan to share: No
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Started Sep 2024 (actual). Primary completion is estimated for Dec 2027, 39 months after the start.
Of 47 non-industry interventional studies with no phase under Bradycardia, half reached primary completion within 28 months of starting (the median), counting those still running; a quarter within 12 and three quarters within 59. This study's planned 39 months is above that.
Counting every sponsor, half of 83 studies reached it within 21 months; a quarter within 12 and three quarters within 38.
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Tomsk National Research Medical Center of the Russian Academy of Sciences