Localization of the slow conduction zone during reentrant ventricular tachycardia

Background-Reentrant ventricular tachycardia is sometimes difficult to trea t effectively because localizing the slow conduction zone (SCZ) for cathete r ablation may be problematic. It was hypothesized that a linear relationsh ip exists between activating wave-front acceleration and deceleration in th e SCZ and, respectively, contractions and expansions of the far-field extra cellular signal, which could be used for SCZ localization. Methods and Results-To test the hypothesis, a model was developed to approx imate SCZ location on the basis of the time interval between activation at the recording site and shifts in electrogram far-field deflections. Electro grams were recorded during reentry from 196 to 312 epicardial sites (canine model, 8 episodes). Activation maps of reentry were constructed to determi ne wavefront velocity, and piecewise linear adaptive template matching (PLA TM) measured time shifts in far-field electrogram deflections. Linear trend s of cycle length change often occurred during tachycardia (mean trend, +15 ms/96.8 cardiac cycles; r(2)=0.92). Alteration in the time interval for ac tivation through the SCZ approximated the change in tachycardia cycle lengt h (mean correspondence, 75.7%). The beginning and end times of far-field ex tracellular waveform time shifts measured by PLATM predicted the time from recording site activation to activation at the SCZ proximal and distal edge s, respectively (mean absolute error with respect to activation mapping, 20 .3 ms). Conclusions-During reentry, PLATM estimates the time interval from activati on at any recording site near the circuit to SCZ activation. PLATM time int ervals are convertible to are lengths along the circuit for potentially mor e rapid and accurate update of a hand-held probe toward the SCZ for cathete r ablation.