Conduction left-to-right and right-to-left across the crista terminalis

Area of Science:

• Electrophysiology
• Cardiac Anatomy
• Arrhythmia Mechanisms

Background:

• The role of the crista terminalis (CT) in atrial flutter (AFL) is debated, specifically whether conduction block is fixed or functional.
• Understanding CT conduction is crucial for elucidating AFL pathophysiology.

Purpose of the Study:

• To test the hypothesis that conduction across the CT is normally present but can become functionally blocked.
• To investigate the nature of conduction across the CT during various atrial rhythms.

Main Methods:

• Simultaneous electrogram recordings from 396 atrial sites in 15 dogs with sterile pericarditis and 7 normal dogs.
• Analysis of atrial activation patterns during right and left atrial pacing, AFL, and atrial fibrillation.

Main Results:

• Conduction across the CT was observed during normal pacing, AFL, and atrial fibrillation.
• Activation wave fronts utilized multiple pathways, including Bachmann's bundle and routes inferior to the vena cava, in addition to the CT.
• No evidence of fixed conduction block across the CT was found.

Conclusions:

• Conduction block in the CT region, as seen in AFL, is functional rather than fixed.
• The CT is a viable pathway for atrial activation, with block being a dynamic process.