Abstract 4370: Ultrasound Balloon Catheter for Mitral Annulus Shrinkage in a Canine Model: Percutaneous Treatment for Mitral Regurgitation
Background: The purpose of this study was to determine whether circumferential endocardial ultrasound (US) energy applications around the mitral annulus (MA) can produce heat-induced shrinkage of MA in a canine model.
Methods: 19 dogs (32–37kg) were studied closed chest. Under fluoroscopy, a 12 Fr US balloon catheter (ProRhythm, Inc) was advanced into the left atrium (transeptal approach). The US balloon was inflated with contrast-water (24mm diameter) and positioned at the MA (Fig⇓). US energy (9MHz) was delivered circumferentially (perpendicular to the catheter shaft) to produce tissue heating around the MA. In 17 dogs, 5 US applications were delivered (60W for 40sec in 2dogs, 80W for 40 sec in 5 dogs, 100W for 60 sec in 5 dogs, 130W for 60 sec in 4dogs, and 130W for 120 sec in 1dog). In remaining 2 dogs, no US was delivered (control group). Transthoracic echocardiogram and Doppler flow were obtained to measure the MA diameter (short and long axes) and mitral flow before, immediately after, and 1, 2, 3, 4 weeks and 3 months after ablation. Dogs were sacrificed at 2 hours (n=7), 4 weeks (n=8) or 3 months (n=4).
Results: In 17 dogs with US delivery, the MA diameter was significantly reduced immediately after ablation (p<0.01, Fig⇓). The MA reduction remained up to 3 month after ablation. In 2 dogs without US, there was no change in MA diameter. There was no significant change in mitral flow (pressure half time and pressure gradient) in any dog. In 10 chronic dogs with US, histology showed minor endocardial thickening of the left atrium close to MA. There was no significant damage of the mitral leaflet or coronary artery.
Conclusion: Endocardial US energy applications around the MA can produce MA shrinkage.