High frame rate ultrasounds for electromechanical wave imaging to characterize and differentiate endocardial from epicardial activation of ventricular arrhythmia: A proof of concept study

Background and objective Differentiating an epicardial from an endocardial ventricular tachycardia (VT) can be really challenging despite the latest technologies available. We intended to develop a new tool method based on electromechanical wave imaging (EWI) to improve arrhythmogenic substrate activation analysis. Methods Experiments were conducted on a left ventricleof a swine isolated working heart model. Our protocol aimed to demonstrate that, thanks to ultrasounds, a different pattern of mechanical activation could be obtained whether the ventriclewas in sinus rhythm, pacedfrom the epicardium or from the endocardium. Results EWI electrocardiogram-gated systematically differentiated with success endocardial from epicardial foci. When in paced ventricle, the origin of the wave front was focal and coming from the endocardiumor the epicardium. In sinus rhythm, wave front was global and activating from the entire endocardiumtowards the epicardium at a speed of 1.47 ± 0.42 ms −1 . Wave front speed through the thickness of the ventriclewas similar when the endocardiumwas paced(1.42 ± 0.38 ms −1 ) and much slower when the epicardium was paced(0.59 ± 0.19 ms −1 ). Conclusion EWI activation mapping can locate ventricular activation inside the left ventricular wall thickness and calculate the propagation of the wave front through the muscle. In the future, this technology might help to differentiate endocardial from epicardial VT during complex ablation procedures.