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Feasibility of intravascular ultrasound ablation and imaging catheter for treatment of atrial fibrillation

Atrial fibrillation (AF) affects 1% of the population and is responsible for 15-20% of all strokes (1); this results in more than 460,000 hospitalizations and a cost of more than $2.8 billion per year. Clinical studies show that circumferential pulmonary vein ablation, a surgical procedure that creates contiguous patterns of lesions that electrically isolate regions of the atria, have been effective in curing AF (2). However, current minimally invasive catheter procedures that use radiofrequency (RF) electrodes under fluoroscopic guidance are often unable to create these contiguous patterns. Difficulties arise in visualizing the anatomy and location of previous lesions and moving the catheter tip to those locations, particularly in the dynamic environment of the heart. Not only can intravascular ultrasound arrays deliver dy- namically, steerable therapy, they can also image the region of interest with good tissue contrast to correctly position the lesion. We propose the use of an intracardiac linear ultrasound array placed at the end of a 7 French catheter. Previously, we showed an intracardiac-sized transducer (20 mm by 2 mm) can create temperature rises of 45 degrees necessary for ablation. In this work, we illustrate the possibility of visualizing such a high intensity focused ultrasound (HIFU) lesion with conventional ultrasound imaging. I. INTRODUCTION An intracardiac ultrasound transducer addresses the issues of precisely positioning lesions and visualizing these lesions and anatomy during the AF procedure. Ultrasound therapy can be dynamically and electronically steered to precise locations as the transducer is roughly anchored in particular position; this dynamic steering can compensate for cardiac motion and variable anatomy. Unlike fluoroscopy, ultrasound imaging also provides real-time images of tissue and lesions with good tissue contrast. This can offer significant improvement in the ability to treat arrhythmias (4), (5), (6). Separate ultrasound imaging probes have been used to guide high intensity focused ultrasound (HIFU) transducers by displaying the anatomy and also detecting past lesions as bright echogenic regions (7), (8), (9). Though these echogenic regions fade 1-2 min after HIFU application, they persist for long enough periods to guide the placement of adjacent lesions for formation of contiguous patterns.