Electrogram characteristics indicative of a recurrent conduction site after ablation of the inferior vena cava-tricuspid annulus isthmus - A study inthe canine blood-perfused atrioventricular preparation

Analysis of the electrograms recorded along the ablation line can identify a recurrent conduction site after ablation of the isthmus between the infer ior vena cava (IVC) and tricuspid annulus (TA) for atrial flutter. The pres ent study examined the relationship between the activation sequence and ele ctrogram characteristics using a model of recurrent conduction in the isthm us. The canine heart was isolated (n=8) and cross-circulated with the arter ial blood of a support dog. A plaque electrode was placed at the isthmus, a nd 42 bipolar electrograms (filtered and unfiltered) were recorded during p acing at 120 beats/min from the lateral right atrium before and after creat ing a narrow gap by 2 discontinuous incisions from the TA to the IVC, All b ipolar electrodes, with the cathode in the TA side and the anode in the IVC side, were placed perpendicular to the TA. Before creating the incisions, the wavefront (WF) from the pacing impulse traveled uniformly in the isthmu s and almost in parallel to the TA, and the filtered electrogram at each si te showed a single potential. After creating the incisions, the WF propagat ed through the gap and spread radially to the area distal to the incisions. In close proximity to the incision lines opposite to the pacing site, the WF advanced from the gap towards the TA and IVC perpendicularly to the TA. Filtered electrograms on the incision lines showed double or split potentia ls, whereas those on the gap showed a single or fractionated potential. In unfiltered electrograms recorded from the TA to the IVC in close proximity to the incision lines opposite the pacing site, reversal of electrogram pol arity was noted at the gap. A single or fractionated potential between doub le potentials indicates a gap between lines of conduction block. Electrogra m polarity reversal along the ablation line indicates the presence of 2 opp osing WF arising from the gap.