Background: The mechanisms underlying atrial tachycardia (AT) caused by electrophysiologic substrates following pulmonary vein isolation (PVI) are not yet well understood.
Objective: The aim of this study was to investigate the impact of the anisotropic conduction properties in the left atrium (LA) on the inducibility of AT.
Methods: A total of 117 patients who had undergone catheter ablation for atrial fibrillation (AF) were enrolled. After PVI, pacing in the high right atrium (100 ppm) was performed during sinus rhythm. The propagation pattern and conduction time of the LA were recorded (forward propagation map [FPM]), and the earliest and latest activation sites in the LA were marked. Pacing (100 ppm) was also performed in the latest activation site in the LA (reverse propagation map [RPM]). Finally, atrial burst pacing was performed to examine the inducibility of atrial arrhythmia.
Results: The earliest activation site taken from the FPM was the same as the latest activation site taken from the RPM in 97 out of 120 patients (Group A: anisotropic conduction: negative). In 20 patients, however, a discrepancy between the earliest activation site taken from the FPM and the latest activation site taken from the RPM was observed (Group B: anisotropic conduction: positive). Sustained atrial arrhythmia was induced via burst pacing in 63 patients (AF:36, AT:27). The inducibility of AF did not significantly differ between Groups A and B (31% vs 25%, p=0.79). However, the inducibility of LA-AT was significantly higher in Group B than that in Group A (80% vs 11%, p<0.001).
Conclusion: The anisotropic conduction property in the LA following PVI may play a key role in the substrate of LA-AT.