Inferior Sino-Atrial Node Exit Sites Are Associated With Electrical Remodeling.

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Anatomy

Background:

• Electrical activity spreads from the sino-atrial node (SAN) through specific atrial pathways.
• Inferior sino-atrial node exit sites (SANi) are observed in patients with structural heart disease and atrial fibrillation.
• Understanding SANi electrical properties and conduction determinants is crucial but limited.

Purpose of the Study:

• To compare unipolar potential morphology and right atrial (RA) remodeling between superior (SANs) and inferior (SANi) sino-atrial node exit sites.
• To investigate electrophysiological differences associated with SANi versus SANs.

Main Methods:

• High-resolution epicardial mapping in 27 patients with structural heart disease undergoing open-heart surgery.
• Classification of electrodes within 8mm of the SAN exit site as the SAN area.
• Computation of electrophysiological properties: potential voltage, conduction block, and R/S ratios.

Main Results:

• SANi (n=7) showed lower potential voltages (1.3 vs 2.6 mV) and rS-wave morphologies, unlike SANs' full S-waves.
• RA total activation times were prolonged in SANi patients (89 vs 78 ms).
• Heart rates were similar and stable across both groups pre- and intraoperatively.

Conclusions:

• Inferior sino-atrial node exit sites (SANi) are associated with extensive right atrial remodeling.
• Altered sino-atrial conduction pathways are the likely cause of SANi findings.
• High-resolution epicardial mapping can identify SANi and associated remodeling.