Model of reentrant ventricular tachycardia based on infarct border zone geometry predicts reentrant circuit features as determined by activation mapping

Background

Infarct border zone (IBZ) geometry likely affects inducibility and characteristics of postinfarction reentrant ventricular tachycardia, but the connection has not been established.

Objective

The purpose of this study was to determine characteristics of postinfarction ventricular tachycardia in the IBZ.

Methods

A geometric model describing the relationship between IBZ geometry and wavefront propagation in reentrant circuits was developed. Based on the formulation, slow conduction and block were expected to coincide with areas where IBZ thickness (T) is minimal and the local spatial gradient in thickness (ΔT) is maximal, so that the degree of wavefront curvature ρ ∝ ΔT/T is maximal. Regions of fastest conduction velocity were predicted to coincide with areas of minimum ΔT. In seven arrhythmogenic postinfarction canine heart experiments, tachycardia was induced by programmed stimulation, and activation maps were constructed from multichannel recordings. IBZ thickness was measured in excised hearts from histologic analysis or magnetic resonance imaging. Reentrant circuit properties were predicted from IBZ geometry and compared with ventricular activation maps after tachycardia induction.

Results

Mean IBZ thickness was 231 ± 140 μm at the reentry isthmus and 1440 ± 770 μm in the outer pathway (P <0.001). Mean curvature ρ was 1.63 ± 0.45 mm⁻¹ at functional block line locations, 0.71 ± 0.18 mm⁻¹ at isthmus entrance-exit points, and 0.33 ± 0.13 mm⁻¹ in the outer reentrant circuit pathway. The mean conduction velocity about the circuit during reentrant tachycardia was 0.32 ± 0.04 mm/ms at entrance-exit points, 0.42 ± 0.13 mm/ms for the entire outer pathway, and 0.64 ± 0.16 mm/ms at outer pathway regions with minimum ΔT. Model sensitivity and specificity to detect isthmus location was 75.0% and 97.2%.

Conclusions

Reentrant circuit features as determined by activation mapping can be predicted on the basis of IBZ geometrical relationships.

Keywords: Arrhythmia, Border zone, Conduction velocity, Infarction, Mapping, MRI, Propagation, Ventricular tachycardia