Electrocardiographic marker of ventricular action potential triangulation (the simulation study).

BACKGROUND

The aim of this simulation was to examine the utility of a novel ECG-based index of cardiac action potential (AP) triangulation, the Tstart-to-Tpeak (TsTp) interval-to-JTstart (JTs) interval ratio, for assessment of changes in AP profile imposed through variations in the duration of the plateau phase and the phase 3 repolarization.

METHODS

ECGs were simulated using a realistic rabbit model based on experimental data. The AP plateau was measured at APD30, and the phase 3 was assessed as APD90-to-APD30 difference (AP durations at 90 % and 30 % repolarization, respectively). AP triangulation was quantified as (APD90-APD30)-to-APD30 ratio. The baseline durations of AP plateau and phase 3 were modified through (1) 50 % shortening, (2) 50 % to 100 % lengthening, and (3) concurrent, non-uniform lengthening in both the AP plateau and phase 3, replicating the long QT syndrome type 2 (LQT2) and type 3 (LQT3) models.

RESULTS

When simulating the isolated changes in either the AP plateau or the phase 3 durations, the (APD90-APD30)-to-APD30 ratios were the same for all model cells. The TsTp/JTs ratios calculated from the simulated ECGs closely approximated the (APD90-APD30)-to-APD30 ratios, despite the lead-to‑lead variability in TsTp and JTs intervals. When simulating the concurrent changes in AP plateau and the phase 3, the (APD90-APD30)-to-APD30 ratios were variable in cells from different layers across the ventricular wall. Nevertheless, the TsTp/JTs ratios were found to be within the range of the minimum-to-maximum values for the (APD90-APD30)-to-APD30 ratio.

CONCLUSIONS

The TsTp interval-to-JTs interval ratio can serve as an electrocardiographic marker of cardiac AP triangulation.