Atrial Tachycardia With Fluctuating Cycle Length Post Multiple Atrial Fibrillation Ablations
A 66-year-old man with five prior atrial fibrillation (AF) ablations was referred for electrophysiological evaluation following recurrent supraventricular tachycardia resulting in tachycardia-induced cardiomyopathy with an ejection fraction of 38%. After dofetilide failure, amiodarone suppressed the tachycardia, and his ejection fraction recovered to 60%. He discontinued amiodarone, fearing long-term side effects. An electrophysiological study was performed, and an atrial tachycardia with two distinct, alternating cycle lengths was easily induced with burst pacing (Figure 1). Attempted entrainment at one location in the left atrium is shown (Figure 2). Ablation at this location resulted in the tachycardia cycle length becoming fixed, and then the tachycardia terminated (Figure 3).
Which of the following statements describes the mechanism of tachycardia?