Sotalol-induced repolarization time heterogeneities in pig hearts and computer models showed that polymorphic ventricular tachycardias are inducible and maintained by reentry along the gradient.
Does repolarization heterogeneity determine the induction and maintenance of torsades de pointes in models of long QT syndrome?
Torsades de pointes arrhythmias are inducible within a critical range of repolarization time heterogeneities and are maintained by reentry wandering along the repolarization gradient.
BACKGROUND: Torsades de pointes arrhythmia is a potentially lethal polymorphic ventricular tachyarrhythmia (pVT) in the setting of long QT syndrome. Arrhythmia susceptibility is influenced by risk factors modifying repolarization. OBJECTIVE: The purpose of this article was to characterize repolarization duration and heterogeneity in relation to pVT inducibility and maintenance. METHODS: Sotalol was infused regionally or globally in isolated Langendorff blood-perfused pig hearts (N = 7) to create repolarization time (RT) heterogeneities. Programmed stimulation and epicardial activation and repolarization mapping were performed. The role of RT (heterogeneities) was studied in more detail using a computer model of the human heart. RESULTS: pVTs (n = 11) were inducible at a critical combination of RT and RT heterogeneities. The pVT cycle lengths were similar in the short and long RT regions. Short-lasting pVTs were maintained by focal activity while longer-lasting pVTs by reentry wandering along the interface between the 2 regions. Local restitution curves from the long and short RT regions crossed. This was associated with T-wave inversion at coupling intervals at either side of the crossing point. These experimental observations were confirmed by the computer simulations. CONCLUSION: pVTs are inducible within a critical range of RT and RT heterogeneities and are maintained by reentry wandering along the repolarization gradient. Double potentials localize at the core of the reentrant circuit and reflect phase singularities. RT gradient and T waves invert with short-coupled premature beats in the long RT region as a result of the crossing of the restitution curves allowing reentry initiation.
Rivaud et al. (Mon,) conducted a other in Long QT syndrome (n=7). Sotalol was evaluated on pVT inducibility and maintenance. Sotalol-induced repolarization time heterogeneities in pig hearts and computer models showed that polymorphic ventricular tachycardias are inducible and maintained by reentry along the gradient.