The canine model with chronic, complete atrio-ventricular block.

Proarrhythmic susceptibility to drug-induced Torsades de Pointes is restricted to individuals with a predisposed phenotype characterized by a reduced repolarization reserve. Additional factors are often involved in a further impairment of repolarization, possibly culminating with dangerous ventricular polymorphic tachyarrhythmias. Drugs that block repolarizing currents represent such an additional hit. The dog model with chronic, complete atrio-ventricular block has been used frequently for proarrhythmic drug screening. The ventricular remodeling seen after ablation of the AV node enhances the susceptibility for repolarization-dependent arrhythmias. In this review, we 1) describe the cellular and molecular basis of ventricular remodeling, 2) validate the CAVB dog as a drug screening model and 3) introduce a new surrogate predictive proarrhythmic parameter: beat-to-beat variability of repolarization.