Reducing Radiation Exposure in the EP Lab

Fluoroscopy has traditionally been used in electrophysiology labs for catheter manipulation during radiofrequency ablation. As we treat more complex arrhythmias through ablation, fluoroscopy times can get excessive. In recent times the necessity of reducing exposure to fluoroscopy in the EP lab has been well documented. Innovative methods have been developed to minimize exposure to X-rays while at the same time maintaining the procedure safety and success rates that we all have come to expect.

Extended fluoroscopy exposure can carry short- and long-term health risks to physicians, lab staff, and patients in the lab. Radiation exposure to patients undergoing prolonged EP procedures can result in skin damage that may be visible from a few days after exposure to a few weeks later. Chronic long-term radiation exposure to electrophysiologists and lab staff can lead to leukemia, eye damage, and other cancers. Controlling the amount of radiation exposure from fluoroscopy equipment to both the patient and physician/lab staff is critical for the long-term health benefit of all in the lab. In this article, we aim to share our experience in using the CartoUnivu Module (Biosense Webster, Inc.) to decrease fluoroscopy use in our electrophysiology laboratory.

About the Technology

We have been using the CartoUnivu Module in our lab for approximately three months. The CartoUnivu Module is an innovative new technology that integrates the Carto 3 mapping system with the fluoroscopic image or cine. It helps to reduce the amount of fluoroscopy used during a procedure by combining still frame fluoroscopy images with 3D electroanatomical Carto 3 maps in one single overlapping view. Without this technology, electrophysiologists have to rely on their 3D mapping image as well as the fluoroscopic image for catheter positioning. With both images overlaid on one screen and properly registered, the CartoUnivu system provides similar information as fluoroscopy on the Carto map, and this can be periodically confirmed by the operator. This makes it safe and easier to rely on this integrated 3D map for catheter positioning instead of using fluoroscopy. Given the ability to view the Carto 3 map overlaid onto the CartoUnivu fluoroscopic image, I am able to navigate to the desired position within the cardiac chamber that I am mapping without using additional fluoroscopy.  

We are always looking to lower risk and increase efficiency in our procedures, so any new technology that we use in our lab must have a workflow that enhances the procedure. The CartoUnivu Module has a very simple and efficient workflow consisting of a small registration step at the beginning of the procedure. Using the registration plate which attaches to the location pad already in use, the operator can register the location pad with respect to the fluoroscopy tube. The physician can then store selected fluoroscopic images and use them for the rest of the procedure. Once these fluoroscopic images are obtained, they are automatically sent to the Carto 3 system and displayed on the screen through the CartoUnivu Module.

Atrial Fibrillation Ablation

In our lab, we perform 500 ablation procedures per year, 50% of which are atrial fibrillation ablations, 30% are SVT ablations, and 20% are ventricular tachycardia ablations. We use the CartoUnivu Module for all our atrial fibrillation and ventricular tachycardia cases, which is approximately 50 percent of our ablation procedures. 

In every atrial fibrillation ablation procedure in our lab, the patient is brought to the EP lab and prepped in the usual fashion. Once ready to obtain femoral access, the lab staff takes the initial registration step required to activate the CartoUnivu Module; therefore, this has little to no impact on my case length. Femoral venous access is obtained, and EP diagnostic catheters are inserted and placed in various intracardiac positions. A diagnostic EP study is then performed and tachycardia inducibility is determined. Based on the finding of the study, a radiofrequency ablation plan is formalized. The NaviStar ablation catheter is inserted and placed in the coronary sinus and system respiratory training is performed to initiate respiratory gaiting of the 3D images. An intracardiac ultrasound catheter is inserted and intracardiac echocardiography images are obtained in the end expiratory phase to increase accuracy. The cardiac chamber margins are then annotated on the system to construct a 3D image of the left atrium and the pulmonary veins. Using intracardiac imaging and fluoroscopy, double transeptal puncture is performed. I generally use a deflectable sheath like the Agilis (St. Jude Medical) or DIREX (Bard EP) along with a standard SL1 sheath. After access is established, pulmonary venography is performed, and fluoroscopy images at 30 degrees RAO, 40 degrees LAO and straight AP are sent to the system and stored for the rest of the procedure. Catheter manipulations and RF ablation are now performed without fluoroscopy; this is only used to confirm catheter positioning periodically and is instantly available if there is a perceived need.

Depending on the type of case, I typically keep the right window on the screen with a complimentary CartoUnivu image and use the left window as my main map, which is constantly manipulated to assess catheter location. We like using the CartoUnivu Module in conjuction with a contrast pulmonary venography. During one of my first pulmonary vein isolation cases using the CartoUnivu Module, we used contrast venography to verify the accuracy of the software. I chose to take an additional RAO and LAO view during pulmonary venography in order to visualize the opacified veins integrated with the left atrial CartoSound map. As depicted in the images, the venogram aligns perfectly with the CartoSound map and further increases my confidence in using the CartoUnivu module to guide catheter position instead of stepping on the fluoro pedal. I believe that because of the accuracy of the Carto 3 system using the CartoUnivu module, I have grown to trust my 3D map more throughout the procedure, leading to an overall reduction in my procedural fluoroscopy times by more than 50%. Before using CartoUnivu, when all catheter manipulation was performed with fluoroscopy, our average procedural fluoroscopy time during AF ablation was approximately 30-60 minutes. It has now been reduced to an average of 15-20 minutes and may continue decrease further as we do more cases and the technology evolves. 

Conclusions

Through the use of the CartoUnivu Module software, in conjunction with the Carto 3 system, we are able to reduce the risks associated with extensive fluoroscopy. I believe that the CartoUnivu Module can provide real value to EP labs currently using fluoroscopy for complex ablation procedures, who are concerned with reducing fluoroscopic exposure, enhancing procedural safety, and improving procedure outcomes. 

Disclosures: Vijay Swarup, MD, FHRS is a paid consultant to Biosense Webster.