Direction-dependent conduction abnormalities in the chronically stretched atria

AIMS: There is increasing evidence of the role direction-dependent conduction plays in the arrhythmogenic interaction between ectopic triggers and abnormal atrial substrates. We thus sought to characterize direction-dependent conduction in chronically stretched atria. METHODS AND RESULTS: Twenty-four patients with chronic atrial stretch due to mitral stenosis and 24 reference patients with left-sided accessory pathways were studied. Multipolar catheters placed at the lateral right atrium, crista terminalis, and coronary sinus (CS) characterized direction-dependent conduction along linear catheters and across the crista terminalis. Bi-atrial electroanatomic maps were created in both sinus rhythm and an alternative wavefront direction by pacing from the distal CS. This allowed an assessment of conduction velocities, electrogram, and voltage characteristics during wavefronts propagating in different directions. While differing wavefront directions caused changes in both chronic atrial stretch and reference patients (P< 0.001 for all), these direction-dependent changes were greater in chronic atrial stretch compared with reference patients, who exhibited greater slowing in conduction velocities (P= 0.09), prolongation of bi-atrial activation time (P= 0.04), increase in number (P< 0.001) and length (P< 0.001) of lines of conduction block, increase in fractionated electrograms (P< 0.001), and decrease in voltage (P= 0.08) during left-to-right compared with right-to-left atrial activation. These direction-dependent changes were associated with a greater propensity for chronically stretched atria to develop atrial fibrillation (P= 0.02). CONCLUSIONS: Atrial remodelling in chronic atrial stretch exacerbates physiological direction-dependent conduction characteristics. Our data suggest that the greater direction-dependent conduction seen in patients with chronic atrial stretch may promote arrhythmogenesis due to ectopic triggers from the left atrium.