https://doi.org/10.1007/s00392-025-02625-4
1Universitätsklinikum Münster Klinik für Kardiologie II - Rhythmologie Münster, Deutschland
Background:
Torsade de pointes (TdP) arrhythmias represent a complex polymorphic ventricular tachycardia that is both life threatening and captivating. While the triggering mechanisms in the course of QT prolongation and dispersion are becoming better understood, their sudden self-limiting termination from apparent disorder remains poorly understood.
Methods and results:
In this work, we used a large data set of over 400 Langendorff experiments in isolated rabbit hearts in which drug-induced QT prolongation, bradycardia, and hypokalemia were used to provoke TdP. After initial screening, 427 TdP episodes were analyzed. These were compared with 701 non-sustained monomorphic VT (mVT) episodes also obtained from Langendorff experiments. The use of 8 monophasic action potential catheters allowed accurate characterization of action potential duration, configuration, and dispersion beyond the capabilities of the surface ECG. To identify the possible mechanisms of arrhythmia termination, the initial triple, middle triple, and terminal triple of ventricular complexes were analyzed at each episode using a dedicated software.
A decrease in spatial dispersion (onset: 136.0ms, middle: 110.0ms (p<0.05), end: 80.7ms (p<0.05)) over the course of the episode could be identified as a predictor of termination of TdP. Likewise, within the last three beats, a sudden significant decrease of dispersion is shown as a predictor of termination (Ddispersion between last to second last beat: -25.5ms (p<0.05)). In parallel, there is a decrease in action potential duration (APD90) until termination (onset: 273.8ms, middle: 182.4ms (p<0.05), end: 177.4ms (p<0.05)). Also, a change in action potential configuration (APD90/50 ratio) in terms of a restitution of action potential triangulation (onset: 1.59, middle: 1.46 (p<0.05), end: 1.55 (p<0.05)) and a decrease in conduction velocity between beats as predictors of termination were observed.
In comparison, the monomorphic VT episodes (mVT) showed no significant changes in action potential duration, configuration, or conduction velocity. Merely, a reduction of dispersion during the tachycardia was shown as a predictor of mVT termination.
Conclusion:
Essential aspects determining the termination of TdP episodes are the recovery of action potential configuration and a decrease in spatial dispersion, conduction velocity, and action potential duration.