Difference between electrical remodelling after pulmonary veins and right atrium appendage pacing

Area of Science:

• Cardiovascular Electrophysiology
• Cardiac Arrhythmias
• Ionic Channel Physiology

Background:

• Pulmonary veins (PVs) are recognized as primary sources of paroxysmal atrial fibrillation (AF).
• Rapid atrial pacing alters cardiac electrophysiology, potentially inducing and sustaining AF.
• Understanding electrophysiological changes in PVs is crucial for AF management.

Purpose of the Study:

• To investigate alterations in atrial effective refractory period (AERP) properties and ionic currents within PVs myocytes.
• To compare these changes in dogs subjected to rapid atrial pacing in PVs versus the right atrial appendage (RAA).
• To correlate observed electrophysiological changes with AF inducibility.

Main Methods:

• Twelve mongrel dogs underwent rapid atrial pacing (500 bpm for 4 h) from either superior left PVs or RAA.
• Electrophysiological studies assessed changes in AERP, dispersion, and rhythm.
• Patch clamp techniques evaluated ionic currents (I(Ca,L), I(to)) in isolated PVs myocytes from paced and sham-operated dogs.

Main Results:

• Rapid atrial pacing significantly shortened AERP in both PVs and RAA pacing groups.
• PVs pacing markedly increased AERP dispersion.
• Both L-type calcium current (I(Ca,L)) and transient outward current (I(to)) densities were significantly reduced, with greater reduction in the PVs pacing group.

Conclusions:

• Reduced I(Ca,L) and I(to) densities provide ionic mechanisms for shortened repolarization and altered rate adaptation in rapid pacing-induced atrial tachycardia.
• These ionic changes, more pronounced in PVs pacing, highlight the critical role of PVs in initiating AF.
• The findings offer insights into the electrophysiological basis of AF initiation and maintenance.