Key result
VF and VT demonstrate ~20% shorter electromechanical delay than sinus rhythm in 3D computational models.
Why the study?
Electromechanical delay had been evaluated during sinus rhythm and ectopic pacing, but data regarding electromechanical delay during other rhythms or arrhythmias were lacking.
Does electromechanical delay differ between sinus rhythm, tachycardia, and ventricular fibrillation in a 3D electromechanical ventricular model?
Does electromechanical delay differ between sinus rhythm, tachycardia, and ventricular fibrillation in a 3D electromechanical ventricular model?
Computational modeling demonstrates that electromechanical delay is shorter during ventricular tachycardia and fibrillation compared to sinus rhythm.
Hypothesis-generating in computational models; leaves open translation to clinical arrhythmia assessment.
Electromechanical delay (EMD) is the time interval between local myocyte depolarization and the onset of myofiber shortening. Previously, researchers measured EMD during sinus rhythm and ectopic pacing in normal and heart failure conditions. However, to our knowledge, there are no reports regarding EMD during another type of rhythms or arrhythmia. The goal of this study was to quantify EMD during sinus rhythm, tachycardia, and ventricular fibrillation conditions. We hypothesized that EMD under sinus rhythm is longer due to isovolumetric contraction which is imprecise during arrhythmia. We used a realistic model of 3D electromechanical ventricles. During sinus rhythm, EMD was measured in the last cycle of cardiac systole under steady conditions. EMD under tachycardia and fibrillation conditions was measured during the entire simulation, resulting in multiple EMD values. We assessed EMD for the following 3 conduction velocities (CVs): 31 cm/s, 51 cm/s, and 69 cm/s. The average EMD during fibrillation condition was the shortest corresponding to 53.45 ms, 55.07 ms, and 50.77 ms, for the CVs of 31 cm/s, 51 cm/s, and 69 cm/s, respectively. The average EMD during tachycardia was 58.61 ms, 58.33 ms, and 52.50 ms for the three CVs. Under sinus rhythm with action potential duration restitution (APDR) slope 0.7, the average EMD was 66.35 ms, 66.41 ms, and 66.60 ms in line with the three CVs. This result supports our hypothesis that EMD under sinus rhythm is longer than that under tachyarrhythmia conditions. In conclusion, this study observed and quantified EMD under tachycardia and ventricular fibrillation conditions. This simulation study has widened our understanding of EMD in 3D ventricles under chaotic conditions.
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Heikhmakhtiar et al. (2020) studied Ventricular Tachycardia and Fibrillation. Tachycardia and ventricular fibrillation vs. Sinus rhythm was evaluated on Electromechanical delay (EMD). In a 3D computational model, electromechanical delay was shorter during ventricular fibrillation (50.77-55.07 ms) and tachycardia (52.50-58.61 ms) compared to sinus rhythm (66.35-66.60 ms).
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