Abstract 1696: Infarct Border Zone Geometry is Predictive of the Location and Characteristics of Reentrant Circuits causing Canine Postinfarction Ventricular Tachycardia
Background: In postinfarction canine hearts, we investigated whether infarct border zone thickness and its transitions could be correlated to reentrant ventricular tachycardia circuits and to discontinuities in sinus rhythm activation.
Methods: In six canine experiments, the LAD artery was ligated to produce a subepicardial infarct. 3–5 days later, activation maps of sinus rhythm and of reentrant ventricular tachycardia induced by extrastimulation were constructed from multichannel electrogram recordings. After electrophysiologic analysis, infarct border zone thickness (T) was measured in the excised hearts by either histologic analysis or magnetic resonance imaging at 5.0mm and 0.4mm resolution, respectively. Locations of functional block lines forming during tachycardia were predicted to coincide with largest ΔTmax/T, which was used as an estimate of the degree of wavefront curvatureρ.
Results: Mean±SE thickness was 172.6±14.4μm at the reentry isthmus and 732.9±37.7μm in the outer pathway of the circuit (p<0.001). The largest ΔTmax/T in the entire infarct border zone overlapped locations of block lines bordering the isthmus (mean error 6.2±0.9mm). The predicted isthmus, based on the thresholded ΔTmax/T, overlapped the actual isthmus determined from activation mapping by 83.1%. Mean sinus-rhythm activation time from recording sites on opposite sides of predicted block line and entrance-exit point location about the isthmus was 23.0±2.6ms and 6.8±1.3ms, respectively (p<0.001). Mean ΔTmax/T was 3.15±0.05mm−1 at functional block lines, and 1.35±0.25mm−1 at isthmus entrance-exit points. Away from the isthmus, mean ΔTmax/T was 0.63±0.13mm−1.
Conclusions: Functional block lines form during reentrant tachycardia at edges of thin infarct border zone regions where thickness increases rapidly. Since ΔTmax/T is proportional to wavefront curvature, functional block may result from a large electrical impedance mismatch.