An atypical roof-dependent atrial tachycardia with a long channel of conduction identified with high-density mapping: pitfall of the conventional assessment of the roof line block

A 60-year-old woman presented for radiofrequency (RF) ablation of an atrial tachycardia (AT) after initial atrial fibrillation (AF) ablation. At the time of the electrophysiological study, the patient was in AT (CL = 245 ms). An activation map with the OrionTM basket catheter and the RhythmiaTM system (Boston Scientific, USA) displayed a dual-loop macro-re-entrant AT with roof-dependent and peri-mitral circuits. RF application to the mitral isthmus terminated the AT with the end point of bidirectional block. Subsequently, we completed the roof line and confirmed block while pacing the left atrial appendage (LAA); the duration from the stimulus to the local activation was 180 ms on the low posterior wall and 190 ms on the high posterior wall. However, atrial burst pacing induced another AT. An activation map displayed an atypical roof-dependent AT (CL = 360 ms), which conducted along a channel on the posterior wall (superior to inferior in direction) involving the roof. Areas on either side of the channel were activated from inferior to superior (Panel 1). Additional RF within the channel successfully terminated the AT (yellow circle inPanel 1) and the duration between the stimulus on the LAA and the high posterior wall extended to 240 ms. A new map during LAA pacing confirmed that no conduction remained on the roof (Panel 2); no other ATs were inducible.
Source: Europace - Category: Cardiology Source Type: research