Overcoming Anatomic Barriers in the Right Ventricular Outflow Tract with 4D Intracardiac Echocardiography and Robotic Magnetic Navigation System
Authors: Dr. Rishi Charate, Dr. Adnan Ahmed, Dr. Dhanunjaya Lakkireddy
Case Synopsis: We report a 56 year old female with frequent monomorphic PVCs of outflow tract origin. PVC burden was 23% with associated LV dysfunction (EF 40-45%). Cardiac MRI with delayed hyper enhancement , T1/T2 weighted imaging along with cardiac FDG PET scan did not show evidence of prior injury, inflammation or ischemia. Patient had significant symptoms from palpitations and shortness of breath. In light of the clinical picture – patient was taken to the EP lab for possible mapping and ablation. RV activation map was done. The PVC localized to the RVOT freewall region. Robotic magnetic navigation (RMN) system (Stereotaxis) was used for mapping and ablation purposes. We also placed a 4D-ICE catheter (NuVision) into the RV and using the distal 360 degree distal tip dialing we were able to visualize the RVOT in greater anatomic detail. The earliest area of the activation localized to the free wall with a deep trabeculation that could only approached by looping the ablation catheter from the pulmonary valve. It was impossible to reach the deep crevice without the visual from the 4D ICE. We were able to reverse loop the RMT open irrigated catheter to get behind the trabeculation where the earliest signal was 30msec pre-QRS. Radiofrequency energy application at 40 watts for a total of 240 seconds completely eliminated the PVC. There was no further recurrence of PVC on Isoproterenol, calcium and phenylephrine.
Discussion: Often times the heavily trabeculated RVOT with deep pouches can create challenges in successfully delivering RF energy during ablation procedures. These structures are not well visualized with a regular 2D ICE even parked at the RVOT. The 360 degree wide scanning capability of the 4D ICE dramatically enhances the visualization of the RVOT anatomy. If delivering appropriate dose of RF in this region becomes difficult and what looks like an obvious site and difficulty eliminating the arrhythmias – mapping on the other side of the septum along with an attempt to visualize the RVOT better using 4D ICE may a reasonable option to consider. RMN provides greater stability and navigation capabilities in overcoming the anatomic barriers for successful ablation.
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