Tips for Creating a Successful Fluoroless Cryoablation Program

There is tremendous value in performing ablations without the use of fluoroscopy. The effects of ionizing radiation exposure, both stochastic and deterministic, have been well documented. These risks are not limited to patients, but shared by the electrophysiologist and other lab personnel, who are estimated to have a 0.5% lifetime risk of cancer from radiation exposure. As such, many EP labs around the world are developing and adopting ways to minimize radiation exposure. Orthopedic injuries are also well documented, and a fluoroscopy-free approach allows the physician and staff not to wear lead for these procedures.

In Fall 2012, Dr. Glassman announced his vision for Mercy Medical Center to perform ablation procedures of all types without the use of fluoroscopy. In February 2013, our EP team performed its first fluoroscopy-free ablation for typical atrial flutter. Within a few months, we were routinely performing right atrial ablations of all types without fluoroscopy, and lead was no longer being used for these procedures. For left atrial procedures, fluoroscopy was still being used for the transseptal puncture, but not for catheter positioning prior to transseptal or for mapping and ablation once left atrial access had been obtained. Fluoroscopy time for left atrial procedures was generally less than two minutes. In 2014, our team performed our first fluoroscopy-free transseptal puncture. By 2015, ablations in all four chambers were being done without fluoroscopy.

At the time, the technique used for atrial fibrillation (AFib) cases was contact force radiofrequency ablation. Dr. Chaudhry joined our group in August 2018, and we introduced cryoablation at our center in October 2018 as an alternative means for pulmonary vein isolation (PVI). In keeping with our vision to be a fluoroless EP lab, we wasted no time in working on ways to perform cryoablation without fluoroscopy. Many of the techniques developed for fluoroscopy-free radiofrequency ablation carried over neatly for cryoablation, with only slight modification. Thus, it took only a month for us to perfect our technique. In November 2018, we performed our first fluoroscopy-free cryoablation PVI, only five weeks into the launch of the program. To our knowledge, this was the first fluoroless cryoablation case in the state of Iowa. In this article, we describe the details of this first case as well as the lessons we have learned from our pursuit.

Case Description 

The patient was a 67-year-old male with coronary artery disease, hypertension, and symptomatic paroxysmal atrial fibrillation with progressively worsening symptoms since his AFib diagnosis in 2016. He was uninterested in antiarrhythmic medications and was a good candidate for PVI. As is routine in our lab, after induction of general anesthesia and intubation, we performed a TEE to rule out a left atrial appendage thrombus. We then proceeded to obtain vascular access, placing two femoral venous sheaths on each side. Once vascular access was achieved, we gave a weight-based heparin bolus and initiated a heparin drip, adjusting the rate periodically as needed to ensure ACT levels >300 throughout the rest of the case.

Through the left femoral vein, we then advanced a diagnostic steerable decapolar catheter (Dynamic Deca, Boston Scientific) into the heart. We tracked the catheter movement from the left femoral vein to the right atrium (RA) with the help of a three-dimensional electroanatomic mapping system (EnSite Velocity Cardiac Mapping System, Abbott), creating 3D geometry of its path from the groin to the heart. We then created 3D geometry of the RA, and in conjunction with electrograms recorded from electrodes on the diagnostic catheter, were easily able to advance the decapolar catheter into the coronary sinus (CS). 

Next, we advanced an AcuNav Ultrasound Catheter (Siemens Healthineers) through the right femoral vein (RFV) and used it to survey the heart. The crista terminalis, tricuspid valve, cavotricuspid isthmus, CS ostium and CS, aortic valve, fossa ovalis, left atrial appendage, the four pulmonary veins, esophagus, and pulmonic valve were all visualized and pericardial effusion was ruled out. 

We then proceeded to perform a transseptal puncture. To do this in a completely fluoroless fashion, we utilized intracardiac echocardiography (ICE) to exchange the 7 French sheath in the RFV for a transseptal SL1 (Abbott) sheath. This entails rotating the ICE catheter clockwise from the “transseptal position” to visualize the right pulmonary veins and applying some posterior tilt and rightward flexion such that the SVC comes into view. In this position, the 0.032-inch J-tipped exchange wire can be visualized going up into the SVC, and a sheath exchange can safely be performed.

Next, we advanced a transseptal needle (71 cm BRK-1 XS, Abbott) through the SL1 sheath, leaving two fingerbreadths of space between the hubs of the needle and sheath. The whole transseptal assembly (SL1 plus BRK-1) was then pulled down under ICE guidance and used to engage the fossa ovalis. Once classic “tenting” of the septum was observed on ICE, a nitinol memory-curve transseptal guidewire (SafeSept^™ Transseptal Guidewire, Pressure Products) was advanced easily through the BRK-1 needle into the left atrium (LA), and under ICE visualization, was gently pushed out the left superior pulmonary vein (LSPV). The BRK-1 was then advanced over the SafeSept wire. Once the SL1 and dilator successfully crossed the septum into the LA, the SafeSept, BRK-1, and dilator were removed.

ICE guidance was used again to advance a 0.032-inch Amplatz Extra Stiff Guidewire (Cook Medical) into the LSPV to maintain left atrial access, and the SL1 was exchanged for the FlexCath Steerable Sheath (Medtronic). LA pressure was recorded from the sidearm of the FlexCath after entering the LA. A circular mapping catheter (20 mm Achieve, Medtronic) was then advanced into the LA through the FlexCath and used to create a three-dimensional shell of the LA and pulmonary veins.  

At baseline, all four veins were electrically connected to the left atrium. The Achieve catheter was then removed from the body and introduced into a 28 mm Arctic Front Advance Cardiac Cryoablation Catheter (Medtronic), and the assembly was then re-advanced into the LA. Utilizing both 3D electroanatomic mapping and ICE imaging, the Achieve catheter was advanced sequentially into each of the pulmonary veins. Once balloon inflation was visualized under ICE, the balloon was advanced to create a seal around the vein ostium. Adequate occlusion of the pulmonary vein ostia was confirmed both by pressure change on the continuous pressure monitoring system and with the help of color Doppler. After confirmation of an adequate seal, cryothermal application was performed sequentially in all four veins. During ablation in the right-sided veins, the decapolar catheter that was initially placed in the coronary sinus was removed and advanced into the SVC for phrenic nerve pacing. Three-dimensional mapping and ICE were used to navigate this catheter into position. The same SVC view used for sheath exchange was used for this purpose. The decapolar catheter was gently advanced until adequate and consistent phrenic nerve pacing was achieved from the CS1-CS10 bipole at an output of 10 V @ 2.0 ms. 

We also monitored esophageal temperatures during the case. The minimum esophageal temperature was 30.6 ºC while ablating at the left inferior pulmonary vein (LIPV) ostium. Cryo delivery was shortened to 100 seconds at the RIPV due to a return temperature of -59 ºC. A second freeze was done here for 120 seconds, with a return temperature of -57 ºC. At the end of the case, PVI was assessed and confirmed across each vein.

ICE was then used to examine the pericardial space, and once the ACT was reversed with protamine, the catheters were removed, and hemostasis was achieved with direct manual compression. Despite being our first experience with fluoroless cryoablation PVI, the whole procedure took only a little over three hours. There were no complications. 

Discussion 

Relative to radiofrequency ablation, cryoablation has some unique aspects, such as confirming pulmonary vein balloon occlusion. However, many steps (such as the transseptal puncture) are common to both techniques. Therefore, Dr. Glassman’s experience with fluoroscopy-free RF PVI made it much easier for us to adopt a similar approach with cryoablation. We found that most of the techniques used to perform radiofrequency ablation without fluoroscopy translate easily to the cryoablation technique, with only a few nuanced modifications. These mainly stem from differences in the way that the catheters appear on ICE due to differences in catheter size and ultrasound reflectivity, how they interact with one another on 3D mapping, and due to the desired “low anterior” position of the cryo transseptal. The major aspect that required experimentation was finding the best surrogate to contrast injection to verify balloon occlusion of the pulmonary vein. We experimented with color flow Doppler, saline injection, and visualization of the pressure waveform. We found that use of the pressure waveform alone has been entirely satisfactory for achieving the desired result. It took us about five weeks to successfully complete our first fluoroless cryoablation PVI case; since then, fluoroscopy-free cryoablation has become routine and we no longer wear lead for these procedures.

Just as other senses in the body grow stronger when one is compromised, it is important to make full use of all other modalities at hand when eliminating fluoro use during a case. With practice, relying on modalities such as ICE, 3D mapping, pressure waveforms, and even the sense of “feel”, fill in extraordinarily well for the missing x-ray images. However, there are rare occasions when a quick tap of fluoro is still helpful to confirm a doubt or overcome a particular challenge. With time, this becomes extremely rare.

In general, we have found fluoroless AFib ablations to be safe and effective. We measure all complications each quarter, and have seen our complication rate decrease versus prior to 2012. One of the main impediments preventing operators from adopting a fluoroless approach is the concern for a longer procedure time. However, we noted no significant difference in times between our recent fluoroless cases and the cases we performed earlier with fluoro guidance. While our first fluoroscopy-free cryoablation took 3 hours, we now perform the procedure in 90-120 minutes from lidocaine to sheath pull. Furthermore, we have adapted our techniques to other cath lab procedures, including PFO closure and right heart cath.

Summary

To the best of our knowledge, our experience with fluoroless cryoablation is the first of its kind in the state of Iowa. Our experience is in line with other labs around the country that have demonstrated that cryoablation PVI can be safely, effectively, and efficiently performed without the use of fluoroscopy.

There are many advantages to such an approach. Radiation exposure — with its known risks to the patient, electrophysiologist, and other lab personnel — can be eliminated altogether. Moreover, it eliminates the need to wear lead, which has the potential to cause orthopedic injuries over time.

We share our experience in the hope that it motivates other labs around the country who are considering adopting a fluoroless approach to cryoablation for atrial fibrillation. We are happy to offer our help if needed. 

Disclosures: The authors have no conflicts of interest to report regarding the content herein.