Arrhythmia Inducibility in the CAVB Dog Model, A Critical Analysis on Underlying Factors.

The dog with chronic atrioventricular block (CAVB) combines a number of risk factors associated with Torsade de Pointes (TdP) arrhythmias. Nevertheless, approximately 33% of the animals are resistant to dofetilide-induced TdP arrhythmia. Of a group of 78 experimentally identical CAVB dogs, we compared TdP inducible vs. non-inducible animals for a set of basic, and cardiac electrical and mechanical parameters. Body weight, but not sex or age, is associated with TdP inducibility. Of the cardiac parameters, longer ventricular repolarization duration and increased contractility at baseline are associated with dofetilide-induced TdP arrhythmias. Differences in cardiac parameters disappeared upon dofetilide infusion. We discuss that prolonged repolarization and increased contractility may be early indications of calcium-mediated early after depolarization that may develop into TdP arrhythmias.