Global endocardial electrical restitution in human right and left ventricles determined by noncontact mapping

OBJECTIVES This study was aimed at evaluating global characteristics of electrical restitution in the human ventricle using noncontact mapping. BACKGROUND Steep action potential restitution (slope > 1) and conduction velocity (CV) restitution have been linked with propensity to ventricular fibrillation, but clinical measurement of global electrical restitution had not been feasible. METHODS Activation-recovery interval (ARI) and CV restitution curves were simultaneously constructed from 16 regional segments of the left and right ventricles in 8 patients (6 male, 2 female, age 42 +/- 17 years) following successful ablation of idiopathic ventricular tachycardia in the absence of structural disease guided by the Ensite 3000 system (Endocardial Solutions Inc., St. Paul, Minnesota). The ARIs were determined from reconstructed unipolar electrograms as validated with monophasic action potential recordings. The ARI restitution slopes were determined using the overlapping least-squares linear segments. RESULTS Global electrical restitution curves were heterogeneous in shape and distribution. ARI restitution slope was > 1 at 25% of 128 sites. The overall mean slope was 0.79 and was greater in the left than the right ventricle (0.93 +/- 0.49 vs. 0.65 +/- 0.26, p < 0.001). Dispersion of ARI restitution slopes increased with decreasing diastolic intervals. The CV restitution operated over a narrower range of diastolic intervals compared with ARI restitution, reaching a plateau (10 +/- 6 ms vs. 38 +/- 13 ms, p < 0.001) after refractoriness. The magnitude of CV restitution was also greater (steeper) than ARI restitution (25 +/- 10% vs. 18 9%, p < 0.001). CONCLUSIONS Noncontact mapping can be used to examine global electrical restitution in the human ventricle. The ARI restitution is heterogeneous, with a slope > 1 at 25% of all sites. The heterogeneity of ARI and CV restitution may be important in determining myocardial electrical stability.