The role of pulse timing in cardiac defibrillation

Abstract

Life-threatening cardiac arrhythmias require immediate defibrillation. For state-of-the-art shock treatments, a high field strength is required to achieve a sufficient success rate for terminating the complex spiral wave (rotor) dynamics underlying cardiac fibrillation. However, such high energy shocks have many adverse side effects due to the large electric currents applied. In this study, we show, using 2D simulations based on the Fenton-Karma model, that also pulses of relatively low energy may terminate the chaotic activity if applied at the right moment in time. In our simplified model for defibrillation, complex spiral waves are terminated by local perturbations corresponding to conductance heterogeneities acting as virtual electrodes in the presence of an external electric field. We demonstrate that time series of the success rate for low energy shocks exhibit pronounced peaks which correspond to short intervals in time during which perturbations aiming at terminating the chaotic fibrillation state are (much) more successful. Thus, the low energy shock regime, although yielding very low temporal average success rates, exhibits moments in time for which success rates are significantly higher than the average value shown in dose-response curves. This feature might be exploited in future defibrillation protocols for achieving high termination success rates with low or medium pulse energies.

Optimising low-energy defibrillation in 2D cardiac tissue with a genetic algorithm

“…Further optimisation of anti-fibrillation control may be achieved by proper timing of the application of the pulse sequence, as it has recently been shown that the timing of single-shock termination has a significant influence on the probability of success ( Ji et al, 2017 ; Steyer et al, 2023 ).…”

“…Progress has also been been made combining experimental data with numerical modelling, for example, for studying spatiotemporal alternans patterns of cardiac excitation ( Loppini et al, 2022 ). Recent numerical studies have shown that pulse timing is crucial for termination success ( Steyer et al, 2023 ). Furthermore, chaotic cardiac arrhythmias may exhibit self-termination ( Rappel et al, 2022 ), a phenomenon also seen with chaotic transients in generic excitable media ( Lilienkamp et al, 2017 ; Lilienkamp and Parlitz, 2018 ; Aron et al, 2019 ).…”

Chaos control in cardiac dynamics: terminating chaotic states with local minima pacing

“…Exemplary snapshots of the transmembrane potential V m during spiral wave chaos are shown in Figure 1 for each model, respectively. As done in previous publications on pacing protocols, we also neglect the influence of the fibre orientation in the myocardium, assume absence of scar tissue and except for the MSA model, healthy electrophysiological behaviour of the ion channels within the myocardium ( Trayanova, 2006 ; Janardhan et al, 2014 ; Buran et al, 2017 ; Hornung et al, 2017 ; Lilienkamp and Parlitz, 2020 ; Lilienkamp et al, 2022a ; Lilienkamp et al, 2022b ; DeTal et al, 2022 ; Steyer et al, 2023 ).…”

“…During the pacing process, the dynamics of the system is neglected, as the predetermined pulse frequencies are kept fix. However, Steyer et al showed that the exact timing of a single pulse plays a major role for a successful termination of a chaotic state ( Steyer et al, 2023 ). Additionally, the accuracy of the calculated pulse frequencies is inherently limited by the time period for which the system is observed prior to pacing ( B Traykov et al, 2012 ), as ADP and EquiDist are based on the frequency spectrum of the underlying dynamics and, respectively, its dominant frequency.…”

“… Otani et al, 2019 performed 3D simulations on a simplified ventricular geometry, to show the impact of the direction of an external electrical field on the success rate for defibrillation. Other protocols aim to apply either single stimuli at specific points in time ( Trayanova, 2006 ; Steyer et al, 2023 ) or pulse sequences at predefined periods/frequencies ( Fenton et al, 2009 ; Janardhan et al, 2014 ; Buran et al, 2017 ; Hornung et al, 2017 ; Lilienkamp et al, 2022a ; Lilienkamp et al, 2022b ; Aron et al, 2023 ). The timing of pulses can also be determined by feedback-controlled protocols, which incorporate the underlying dynamics and the reaction of the system to stimuli.…”