Entrainment mapping: Theoretical considerations and practical implementation
The majority of tachyarrhythmias targeted for ablation are due to re‐entry. Identification of potential targets for catheter ablation is facilitated by definition of the propagation pathways. These can be defined by activation sequence mapping with analysis of wavefront propagation in relation to anatomical structures, but this requires extensive recording during the tachycardia with sampling from multiple sites or use of a complex multielectrode mapping system. To reduce the sampling required during the arrhythmia, substrate mapping and entrainment mapping can be employed and, for scar‐related ventricular tachycardias, are usually used in combination. Substrate mapping is the identification of potential re‐entry circuit pathways, commonly defined by regions of fibrosis, during sinus or a stable paced rhythm. The extent to which activation mapping and entrainment mapping can be applied depend on the stability of the arrhythmia and the hemodynamic stability of the patient.
Entrainment for interrogation of reentrant arrhythmias was first described in 1977 by Waldo et al.1 and has been intensively studied over the subsequent 40 years. Discussion of all of the uses of entrainment for diagnosis and mapping would exceed the scope of this article. Rather, general physiology and strategies for its application will be introduced to interpret entrainment maneuvers, diagnose re‐entry mechanisms, determine the spatial relation of particular pacing sites to a re‐entry circuit and to identify appropriate ablation targets.