Fig. 4.
Reentry induced by an ectopic beat. A: 705 ms. A sinus beat originated at the His bundle at a fixed interval (tHis) = 700 ms (black arrow), following an ectopic activation in the right PS (tEB = 370 ms). B: 731 ms. Due to refractoriness in the RBB from the premature beat, sinus activation propagated into the left PS and ventricle but not into the right PS due to temporary CB. C: 800 ms. Activation spread across the septum from LV to RV, and the right distal PS, now fully excitable, was activated by retrograde propagation (white arrow). D: 860 ms. Reentry was initiated. E: individual APs at various locations in the PS. Traces 2 and 3 show conduction of the sinus beat in the LBB, while traces 4 and 5 show CB in the RBB (indicated by asterisks). Dotted line indicates the instance of sinus beat. Labels are as in Fig. 3.