Ventricular mapping during atrial and ventricular pacing - Relationship of multipotential electrograms to ventricular tachycardia reentry circuits after myocardial infarction

Aims Conduction through separated myocyte bundles causes multipotential electrograms and reentrant ventricular tachycardia. We hypothesized that without initiating tachycardia, the reentry region could be detected by analysing the change in multipotential electrograms during two different activation sequences. Methods and Results During catheter mapping and ablation in 16 patients with ventricular tachycardia late after infarction ventricular electrograms were recorded from 1072 Sites during atrial and right ventricular paced ventricular activation. Multipotential electrograms were present during both activation sequences at 285 (27%) sites, during atrial pacing only at 159 (15%) sites and during right ventricular pacing only at 152 (14%) sites. Sites with multipotential electrograms during both activation sequences were more often related to a ventricular tachycardia circuit isthmus (43%) as compared to sites where such electrograms were present during one activation sequence (20%). Multipotential electrograms with >2 low amplitude deflections and a >100 ms difference in duration between the two activation sequences were infrequent but highly predictive of the reentry circuit. Conclusion Regions with fixed multipotentials consistent with conduction block might be useful guides for ablation approaches that target large regions of the infarct, but are not sufficiently specific to be the sole guide for focal ablation approaches.