Isthmus-dependent atrial flutter with unusual activation pattern

摘要

An 86-year-old man with history of dual-chamber pacemaker placement for intermittent second-degree atrioven-tricular block was referred for electrophysiology study and ablation for recently diagnosed symptomatic atrial flutter. There was no history of ablation or cardiac surgery. The baseline electrocardiogram showed atrial flutter (Figure 1A). Intracardiac electrograms showed an atrial flutter with tachycardia cycle length (TCL) of 316 ms, distal to proximal coronary sinus (CS) activation, and high to low right atrial activation (Figure IB). Overdrive pacing from the proximal CS resulted in manifest entrainment with a long postpacing interval (PPI) (170 ms > TCL; Figure 2C). Entertainment from the distal CS revealed a shorter PPI-TCL values of 130 ms (Figure 2D). Distal to proximal CS activation and a shorter PPI from the distal CS vs the proximal CS suggested an arrhythmia originating in the left atrium.