Electro-tomographic method to determine true north: Novel transmural mapping strategy for inappropriate sinus tachycardia ablation.

Here we report a novel electroanatomic mapping method to determine intramural activation, which we call electro-tomographic mapping. Based on our previous experiments, which demonstrated that multipolar electrograms can resolve near-field activity with little contamination in the x/y-plane but with a confocal view in the z axis, we designed a strategy for identifying activation from a focal source deep to the mapping surface through a combination of annotating the earliest -dV/dtmax and identification of a multipolar QS signal. We hypothesized that this strategy would be of use to map the true superior "North" sub-epicardial activation of the sinoatrial node (SAN) to facilitate catheter ablation in a challenging case of inappropriate sinus tachycardia. This patient had a previous unsuccessful catheter ablation due to proximity of the "earliest" site as identified by traditional mapping (unipolar QS, earliest -dV/dtmax) to the phrenic nerve. We found that electro-tomographic mapping could be used to track the epicardial focus of activation of the SAN superiorly, with increasing heart rate response to isoprenaline. At a heart rate of 110 bpm, dual breakout of "early" activation was noted with a unipolar QS at each region. The ideal site for ablation was determined by examination of the multipolar electrogram for a QS pattern, suggesting that this location was perpendicular to the subepicardial activation of the SAN. This site was away from phrenic nerve and catheter ablation was successful. This technique has wide-ranging potential applications for treatment of cardiac arrhythmias as it opens the door for transmural true 3D mapping. Future construction of mapping arrays with special electrode arrangements will allow for seamless interrogation of the intramural space while mapping the endocardium.