Sinus node, phrenic nerve and electrical connections between superior vena cava and right atrium: lessons learned...

Area of Science:

• Electrophysiology
• Cardiac Ablation Techniques
• Anatomical Mapping

Background:

• Superior vena cava (SVC) isolation during atrial fibrillation (AF) ablation carries risks of sinus node and phrenic nerve injury.
• Limited understanding exists regarding the precise spatial relationships between SVC-right atrium (RA) electrical connections, sinus node, and phrenic nerve in individual patients.

Purpose of the Study:

• To investigate the anatomical and electrical spatial relationships of the sinus node, phrenic nerve, and SVC-RA electrical connections.
• To inform safer strategies for SVC isolation in AF ablation.

Main Methods:

• Eighty-seven AF patients underwent pre-ablation mapping.
• Sinus node sites were identified using RA activation mapping during sinus rhythm.
• Phrenic nerve sites were localized via pacing maneuvers.
• SVC electrical connections were mapped using a circular mapping catheter during ablation.

Main Results:

• The sinus node consistently located at the anterior-lateral SVC-RA junction.
• Phrenic nerve sites predominantly found in the lateral SVC-RA segment.
• An average of 1.8 electrical connections per patient were identified, primarily on the anterior septum, anterior wall, and posterior septum of the SVC-RA junction.
• SVC isolation was successful in all patients with low complication rates (sinus bradycardia, SVC stenosis, phrenic nerve palsy).

Conclusions:

• Sinus node, phrenic nerve, and electrical connection sites are generally predictable at the SVC-RA junction.
• Electrical connections are spatially distinct from the sinus node and phrenic nerve.
• RA activation mapping and SVC pacing effectively localize critical structures, facilitating safe and successful SVC isolation.