Methods
A novel 9 French 4D ICE catheter (VeriSight Pro®, Philips, Andover, MA) (Figure 1) was utilized by three different operators, each with extensive experience with the use of 2D ICE during EP procedures. This catheter incorporates the same ultrasound technology as a 4D TEE probe, miniaturized to fit on the tip of a 3.0mm diameter (9 French) catheter. It has a 90 cm working length with a distal 2 cm imaging tip. The imaging matrix consists of 840 elements (15 x 56 element design). This allows for X-plane imaging with live cross-plane 2D imaging. This matrix also enables 90 x 90 degree volume imaging. The 3D imaging can be obtained in real time; color Doppler can also be added to the live 3D imaging. Another feature is digital steering where the catheter is rotated from the console without the operator moving it manually. There are two steering knobs on the handle (Figure 1C), one for anterior-posterior adjustments and the other for right-left adjustments. There is a separate tension control knob. The articulation segment allows for a 120-degree deflection range in each direction. The catheter connects to the Philips EPIQ CVx imaging console, which can also be used for non-invasive cardiac imaging such as transthoracic echocardiography and TEE.6 Furthermore, the full spectrum of image analysis and post-processing available for TEE is available for ICE imaging including Color Doppler assessment, multiplanar reconstruction and trans-illumination technology.
The catheter was advanced from the left femoral through a 10 French short sheath and positioned in various cardiac chambers during ten interventional EP procedures including catheter ablation and LAAC, during which a standard 2D ICE catheter would ordinarily be used. All procedures were guided with fluoroscopy and performed under general anesthesia. There were no changes to the standard approaches during the EP procedures because of the use of the 4D ICE catheter. A standard TEE probe (Philips) was used as well during the LAAC procedures and images were obtained by the cardiac anesthesiologist. The ICE images were frozen when the procedure was being guided by TEE, and vice versa to prevent artifact during imaging.
The ICE catheter was initially placed in the right atrium (RA). Images were acquired in real time during catheter manipulation by the electrophysiologist, and processed by a dedicated imaging expert at the ultrasound console. Initially views were optimized using a standard 0-degree imaging angle using a combination of manual catheter manipulation and digital steering. In preparation for orthogonal X-plane imaging, views of the same structures were optimized using a -45-degree angle so that orthogonal views would be at +45 and -45 degrees. This approach allowed for better image quality compared to imaging from 0 and +90-degree angles. In a subset of patients, the ICE catheter was placed in the LA and in additional positions to assess its ability to acquire images of the LA and left atrial appendage from other vantage points. The ICE catheter was placed in the LA by advancing it across the same transseptal puncture site as the transseptal sheath using a “shoe-horn” technique without a long sheath.
The VeriSight Pro® 4D ICE catheter is approved for use in humans by the United States Food and Drug Administration (FDA). Procedures were performed after FDA approval, in preparation for a planned registry study that has been approved by the Northwestern Institutional Review Board (IRB) and is sponsored by Philips, the manufacturer of the 4D ICE catheter.