Very High Resolution Near Field Imaging Of Ablation With A Newly-Developed Forward-Looking Catheter Mounted Microlinear Intracardiac Imaging Array

Background: We have developed the first forward-looking highly steerable intracardiac echo probe developed for ultrasound visualization of ablation. It is a 24-element forward-looking microlinear array on a 9 Fr catheter that has additional electrodes so it can be localized compared to separate ablation catheters through electrofield navigation by NavX. Methods: In 4 studies of closed-chest pigs, we have imaged ablation locations in the right atrium and the isthmus and on the right side of the septum and at the right ventricular apex, and also imaged across the septum at ablations in the left ventricle along the septum with this device. Results: Images at 150–170 frames/sec at 12–15 MHz give very high detail of the changes occurring during ablation, including liquefaction, heating changes, brightening and thickening of tissue, and thrombus formation in the adjacent region in unheparinized pigs. The devices are well enough shielded from RF energy that there is little interference, and yet an ablation is being performed. A catheter tip artifact makes it easy to see the actual location of the ablation catheter tip with the microlinear array. Tissue Doppler/strain rate imaging also yields the possibility of determining mechanical changes occurring in ablation where brightening of tissue associated with stiffening diminished mechanical strain deformations in ablated lesions, especially in the ventricles. Conclusions: This new technology provides a new method for guidance and, more importantly, a method for understanding the changes that occur with RF ablations in experimental animals and, eventually, in patients.