Final Report Summary - HIFUSWI-INTRACARDIAC (High-intensity focused ultrasound intracardiac ablation with real-time monitoring using shear-wave imaging) Arrhythmias are a major cause of death and disability worldwide and their prevalence is expected to rise with the aging of the population. Recent technological advances have led to the development of new treatments based on radio-frequency (RF) catheter ablation to treat and even cure these conditions. However, challenges in treatment persist. RF ablation is currently performed via direct contact with the endocardium, limiting the depth of tissue injury unless high temperatures are used, which leads to higher risks of clot formation. Another major limitation is the lack of combined imaging modality for real-time monitoring of the treatment and for accurate assessment of the lesion extent. Our objective is to construct an ultrasound-based intra-cardiac ultrasound therapy/imaging system that can perform ablation using high-intensity focused ultrasound (HIFU) and can monitor the size and temperature of the ablation lesion using shear wave imaging (SWI). The specific aims are 1) to develop an intracardiac hybrid system to perform HIFU, real-time temperature and lesion size monitoring using SWI, 2) Validate and optimize the imaging/therapy system in an animal model and 3) Demonstrate the feasibility of real-time RF ablation monitoring in patients using SWI. Upon completion, this project will result in the development of an intra-cardiac ultrasound system that allows performing non-contact ablation transmurally while monitoring the lesion site growth and temperature in real time. The capability of ablating at any location in the thickness of the myocardium while simultaneously assess the size of the lesion, has the potential to accelerate procedures, reduce the risks, and, provide a new approach to assess the success of the ablation.ResultsObjective 1: Develop an intra-cardiac hybrid system to perform HIFU, real-time temperature and lesion size monitoring using shear-wave imaging. This objective is complete. Indeed, we have implemented the SWI and HIFU sequences and tested them in gel phantoms and in ex-vivo heart samples. The following results were obtained: - Shear waves are generated by the intracardiac transducer at depths of up to 15 mm. - Shear waves are imaged by the same intracardiac transducer at 10 000 images/s- Mapping of the stiffness of radio-frequency lesions was performed in ex vivo cardiac tissues- HIFU ablation was performed in ex vivo samples.Objective 2: Validate and optimize the imaging/therapy system in an animal model by monitoring the growth and temperature of the lesion. We have performed in vivo experiment in two normal sheeps (n=2). The following results were obtained:- Myocardial stiffness was estimated in vivo in atrium and ventricle using the intracardiac transducer- Myocardial stiffness variation over the cardiac cycle could be measured- Mapping of the stiffness after radio-frequency ablation was demonstrated in vivo- The same dual-mode catheter can be used to perform ablation and monitor it in large animals in vivo.Objective 3: Demonstrate the feasibility of real-time RF ablation monitoring in patients using SWI.- We have demonstrated the feasibility of performing SWI transthoracically using a standard phased array probe by using novel harmonic imaging strategies.ImpactUpon completion, this project will result in the development of an intra-cardiac ultrasound system that allows performing non-contact ablation transmurally while monitoring the lesion site growth and temperature in real time. The capability of the hybrid system of ablating at any location in the thickness of the myocardium while simultaneously assess the size and temperature of the lesion, has the potential to accelerate procedures, reduce the risks, and provide a new approach to assess the success of the ablation. In turn, this technology could reduce the number of cases of recurrence of arrhythmias following an ablation procedure. Indeed, instead of approximately positioning a RF catheter at the site of ablation, the user would have the option of simply indicating, through, e.g. a mouse click, the region to ablate on the ultrasound system. Immediately, an image of the lesion size and a temperature map would appear overlaid onto the B-mode image to monitor the amount of energy to be sent to the tissue. Finally, this approach is highly translational, as intra-cardiac ultrasound imaging is already commonly used by electrophysiologists. Dissemination activitiesThe project and its results were presented in a large number of international conferences and at invited talks in universities around the world.
