1. Takekuni Hayashi et al. JACEP 2016;2:27-35
Pseudo-Conduction Block of the MI With MB Epicardial Connections The activation sequence of coronary sinus (CS) during left atrial appendage (LAA) pacing is proximal to distal (A, left panel). The conduction time (115 ms) from the distal CS (CS 1 to 2) to the LAA during the CS 1 to 2 pacing was longer than the conduction time (90 ms) from the proximal CS (CS 7 to 8) to the LAA during CS 7 to 8 pacing (B), suggesting complete mitral isthmus (MI) block. However, the LAA activation sequence during CS 1 to 2 pacing was different than the LAA activation sequence during CS 7 to 8 pacing, which suggested 2 or more pathways (via the mitral annulus [MA] and Marshall bundle [MB] epicardial connections) for propagation from the CS to the LAA during CS pacing (i.e., incomplete MI block) (B and C). The conduction time from the distal CS pacing site to the LAA can be longer than from the proximal CS pacing site to the LAA, which can be misleading and misinterpreted as a complete MI block. Radiofrequency ablation was attempted at the ridge and successfully disconnected the connections between the MB and LA, which was demonstrated by changing the VOM sequences during the LAA pacing from distal to proximal to proximal to distal (A, left panel). After ridge ablation, the conduction times from the CS pacing site to the LAA were prolonged, and the activation sequences of the LAA during CS 1 to 2 pacing changed to match the CS 7 to 8 pacing, which indicated the presence of a single conduction pathway via MA from the CS to the LAA during CS pacing (i.e., there was a complete MI block) (D). ABL = ablation catheter; RAO = right anterior oblique; VOM = vein of Marshall.
Takekuni Hayashi et al. JACEP 2016;2:27-35
American College of Cardiology Foundation