An Acute Experimental Model Demonstrating 2 Different Forms of Sustained Atrial Tachyarrhythmias

BACKGROUND: The objective of this study was to develop an acute experimental model showing both focal and macroreentrant sustained atrial fibrillation (AF). METHODS AND RESULTS: In 31 anesthetized dogs, bilateral thoracotomies allowed the attachment of electrode catheters at the right and left superior pulmonary veins, atrial free walls, and atrial appendages. Acetylcholine, 100 mmol/L, was applied topically to either appendage. Sequential radiofrequency ablation was achieved for the ganglionated plexi (GP), found adjacent to the 4 pulmonary veins. In 12 separate studies, a propafenone bolus, 2 mg/kg, was given before and after GP ablations at the start of acetylcholine-induced AF. Acetylcholine caused abrupt onset of AF (n=22) or induced AF by burst pacing (n=9) that lasted > or = 10 minutes. Rapid, regular, or fractionated atrial electrograms were consistently seen (average cycle length, 37+/-7 ms) at the appendages versus cycle lengths of 114+/-23 ms at other atrial sites. After ablations of GP, AF abruptly terminated (n=25). In 6 dogs, sustained atrial tachyarrhythmias continued. Pacing at specific atrial sites organized electrograms of one atrium or also captured the other atrium. The latter resulted in termination when pacing was stopped in 4 of these 6 experiments. Propafenone did not change the duration of focal AF before GP ablation (17+/-9 versus 14+/-8 minutes; control, P=0.6) but terminated reentrant atrial tachyarrhythmias (12+/-3 versus 2+/-1 minutes, P=0.0009). CONCLUSIONS: Before GP ablation, acetylcholine (100 mmol/L) induced sustained AF characterized by rapid, focal firing. GP ablations were associated with loss of focal firing and regularization of electrograms in both atria before termination. Propafenone failed to terminate focal AF but rapidly terminated entrainable macroreentrant atrial tachyarrhythmias.