Biophysical modelling of bundle branch reentry initiation and maintenance

Bundle branch reentry (BBR) is a complex triggering mechanism of ventricular tachycardia, which initiation and maintenance are not well understood. We present a multi-scale functional model of the His bundle and bundle branches coupled to a simplified representation of the septum to study initiation and maintenance of BBR in-silico. The model includes a pathological region in the base of the left bundle branch characterized by a lower IKr current and a lower conductivity. The effect of the size of the pathological region and the percentage of IKr block have been studied to determine their potential role in BBR initiation and maintenance. Both characteristics together with sudden changes in pacing frequency affected the triggering and perpetuation of a BBR. We conclude that a pathological basal region in a bundle branch, characterized by larger APD and refractory periods can induce and perpetuate BBR when a short-to-long BCL change occurs after the conduction block.