Objective: The roles of electrical restitution determined by epicardial contact mapping and surface electrocardiogram (ECG) in the inducibility of ventricular fibrillation (VF) were evaluated.
Methods: Ten epicardial unipolar electrograms using contact mapping and the surface ECGs were simultaneously recorded in 7 swine. Activation-recovery interval (ARI) and QT-interval restitution curves were constructed. Steady-state pacing protocol was performed to induce VF. Ventricular fibrillation threshold was defined as the longest pacing interval for inducing VF. Statistical correlation analysis was performed to determine the relationship between local ARI restitutions, QT-interval restitution, and ventricular fibrillation threshold.
Results: One hundred thirteen restitution curves were constructed (50 in left ventricular sites, 52 in right ventricular sites, and 11 in surface ECG lead II) from 11 steady-state pacing procedures. Statistical correlation between the slopes of the QT restitution curve and the slopes of regional ARI restitution curves was noted in several mapping sites. Ventricular fibrillation threshold significantly related to the local ARI restitution curve slope for the right ventricular apex (R = 0.752, P = .019) and the QT-interval restitution curve slope (R = 0.802, P = .005).
Conclusion: There is a significant correlation between the local ARI restitutions and the QT-interval restitutions, both of which were associated with VF inducibility.