Detecting Local Myocardial Spatiotemporal Repolarization Gradients With Clinical Mapping Arrays

Activation recovery interval (ARI), extracted from unipolar electrograms, serves as a practical surrogate for repolarization during experimental studies in vivo. Far-field signal contamination and low spatial resolution obscure regional repolarization gradients and duration alternans detection using unipolar ARI. We hypothesized that the attenuation of far-field contamination with the principal component-referenced unipole will allow for a more accurate assessment of true local repolarization gradients and spatially assess action potential duration alternans.

Unipolar ARI and the novel method, Repol^Loc, were validated for the detection of spatial and temporal repolarization changes using simultaneous optical and electrical mapping in a rabbit Langendorff model. Repolarization changes were created using global infusion of ibutilide or pinacidil, or topical application of lidocaine. Epicardial mapping was conducted in a porcine Langendorff model following the topical application of lidocaine to investigate the spatial resolution of each method. Generalized linear models of the two methods were used to compare with optical action potential duration (APD80).

Following the infusion of antiarrhythmic drugs, the Repol^Loc method (slope=0.90) had a slightly higher correlation to optical APD80 than the ARI method (slope=0.79). Following regional application of lidocaine, Repol^Loc was better able to localize the site of drug administration with an average 26.12% reduction as compared with 18.66% reduction in unipolar ARI (P=0.0046). Additionally, temporal repolarization alternans and restitution changes assessed by Repol^Loc method tracked optical APD80 quantified time domain changes.

Repol^Loc has higher sensitivity to local spatiotemporal repolarization heterogeneities and alternans than traditional ARI. Although ARI only correlates with uniformly distributed changes in repolarization in the entire myocardium, Repol^Loc also provided accurate regional gradient assessment and duration alternans of repolarization. These findings suggest ARI has significant far-field contamination and Repol^Loc may provide a better clinical mapping tool for spatiotemporal repolarization gradient mapping.