DISCUSSION
Our pilot study was conducted to compare ICE and IVUS for real-time LA wall imaging and for detection of acute tissue changes produced by different ablation energies during PVI catheter ablation. Although both ICE and IVUS probes image in the axial plan, providing cross-sectional images of the vessel (or chamber of interest) and surrounding tissues, their transducers use different ranges of ultrasound frequencies. The catheter designs are also different: the IVUS catheter has a smaller size (6F) and uses a mono-rail system, with the distal portion of the catheter advanced over a guidewire for better support and stability, while the ICE catheter has a bigger size (9F) and no central lumen. We chose to compare a 9MHz ICE catheter with a 20MHz IVUS probe to investigate which ultrasound frequency would give the best compromise between contrast resolution and image penetration for PVs imaging.