Improving Ventricular Arrhythmias Treatment Monitoring using Ultrafast Ultrasound
Résumé
<b>Context:</b> Ventricular arrhythmias are heart rhythm disorders triggered by specific regions of the ventricles. In most severe cases, these regions must be electrically isolated using radiofrequency (RF) thermal ablation. Catheter-based mapping techniques are used for RF treatment planning and control but they remain invasive, time-consuming and based on indirect assessments, amongst other limitations. Ultrafast ultrasound offers various possibilities which could be used in real-time to improve RF ablation monitoring, namely Electromechanical Wave Imaging (EWI) and Passive Elastography (PE). Here, we demonstrate that EWI can be used to identify arrhythmogenic foci on isolated perfused heart models and that PE can monitor thermal lesion formation on cardiac tissue samples. <b>Methods:</b> Two isolated perfused swine heart models were set up to mimic cardiac electrophysiological behavior. Pacing electrodes were screwed on the left ventricle to simulate arrhythmogenic foci. 54 EWI acquisitions were performed in a single cardiac cycle (4000 fps, 15MHz ultrasound probe). 6 thermal lesions were achieved in veal heart wall samples. Shear wave field was created in the tissue with a vibrator on sweep mode. PE acquisitions (600 fps, during 1s, 3MHz ultrasound probe) were performed before and after ablation to visualize elasticity modification induced by thermal lesions in the tissue. <b>Results/Discussion:</b> In this study, ultrafast ultrasound was used in two different ways which could help improve arrhythmias treatment monitoring. EWI allows visualizing propagation of the electromechanical wave in the heart, which could help define ablation target with high precision. By analyzing cardiac activation pattern with EWI, three blind readers were able to accurately retrieve cardiac electrical activation in 78% of the cases. PE demonstrated a local tissue stiffening after lesion formation on 83% of the cases. Transmural lesions were also visualized using PE and confirmed by gross pathology. PE could have the potential to directly monitor RF lesion formation in real-time.