Fluoroless Catheter Ablation: Taking Steps Forward Using the Cryoballoon

Conventional catheter ablation of cardiac arrhythmias has traditionally been performed under fluoroscopic guidance. The use of fluoroscopy, however, comes with radiation risks to the patient as well as to the electrophysiology (EP) laboratory staff. Radiation exposure has been linked to an increased incidence of malignancies, skin injuries, genetic defects, and cataracts. With an increasing number of arrhythmias with indications for catheter ablation as well as newer technologies and methods that aim to make such procedures safer and more effective, more patients are undergoing catheter ablation procedures for atrial fibrillation (AF), atrial tachycardia (AT), and ventricular tachycardia (VT). Long procedure and fluoroscopy times, the use of pre-procedural CT scans to define cardiac and extracardiac anatomy, and a need for multiple procedures are all factors that affect a patient’s cumulative lifetime radiation exposure. Another negative consequence of the use of fluoroscopy during catheter ablation is the increased risk of orthopedic injury for EP staff members due to the use of heavy protective lead garments. 

To best address these radiation- and orthopedic-related risks, fluoroscopy should be minimized and ideally eliminated during EP procedures. By maximizing the utility of 3D electroanatomic mapping (EAM) and intracardiac echocardiography (ICE), most EP procedures can be performed safely and effectively without the use of fluoroscopy. Three-dimensional EAM allows the operator to visualize catheter positioning within the heart in multiple projections, while ICE facilitates direct visualization of most intracardiac structures. ICE also serves as a means of assessing tissue apposition and lesion formation during catheter ablation. 

In July 2010, I performed my first completely fluoroless catheter ablation procedure for a case of atrial flutter. In 2012, I reported on the safety, efficacy, and feasibility of performing fluoroless catheter ablation on an unselected patient group bearing a variety of arrhythmias that presented to our electrophysiology laboratory. In the study, the arrhythmias we successfully ablated using the fluoroless technique included AVNRT, AVRT, atrial flutter, AT, AF, and VT. Also included in the study were patients with cardiac pacemakers and defibrillators (including CRT devices), who underwent successful fluoroless catheter ablation. For those individuals, we successfully avoided lead dislodgement through the use of ICE. 

Since that first fluoroless catheter ablation back in 2010, I have honed and refined the fluoroless method. I am pleased to say that since December 2010, my team has not used any fluoroscopy during any of our catheter ablation procedures. Our team has successfully performed more than 400 consecutive fluoroless ablation procedures.

More recently, the advent of cryoballoon (Arctic Front Advance^™, Medtronic) ablation for AF ablation has presented a single-delivery approach to pulmonary vein isolation that may offer some practical benefits to point-to-point radiofrequency ablation. Once learned, the cryoballoon ablation technique is often thought of as simpler and easier to master for less experienced operators than the point-to-point technique of radiofrequency ablation. As more operators become comfortable with this technique, the number of cryoballoon ablation procedures performed has been steadily increasing. Finding a way to perform these procedures with minimal to zero fluoroscopy would be of great benefit to the patient and EP lab staff. 

With such an aim in mind, in March 2014, I performed my first cryoballoon ablation procedure for atrial fibrillation and did so without the use of fluoroscopy. As our laboratory was already very comfortable performing fluoroless radiofrequency ablation and with many of the elements of the fluoroless cryoballoon and radiofrequency ablation procedures being similar, my staff and I built on our experience as we encountered this new technology. 

Earlier this year, I reported on the first 5 consecutive patients with drug-refractory paroxysmal AF who underwent fluoroless cryoballoon ablation by my team. We achieved pulmonary vein isolation in all 5 patients and there were no major complications. To my knowledge, this report is the first of successful cryoballoon ablation without the use of fluoroscopy. 

The process for performing a completely fluoroless cryoballoon ablation procedure has been refined over the last few months. As it stands currently, after obtaining vascular access, an ICE catheter is usually advanced to the right atrium, while maintaining an echo-free space at the transducer tip. Next, a single transseptal puncture is performed under ICE guidance and hemodynamic pressure monitoring. A deflectable decapolar catheter is then positioned through the transseptal sheath into the left upper pulmonary vein and used as a rail over which the transseptal sheath can be utilized to enlarge the hole. The decapolar catheter is then removed and exchanged for a stiff exchange-length J-wire, which is positioned in the left superior pulmonary vein under ICE guidance. The transseptal sheath is then exchanged for larger caliber Medtronic FlexCath Advance Steerable Sheath. The sheath exchange is performed while maintaining the J-wire in the left superior pulmonary vein under ICE guidance. 

The cryoballoon is then positioned in the left atrium under ICE guidance. We position the 8-pole Medtronic Achieve Mapping Catheter into the left superior pulmonary vein under ICE guidance, and use this circular mapping catheter to create an electroanatomic map. The cryoballoon is then inflated and positioned at the antrum of the vein. The central challenge to performing a cryoballoon ablation without using fluoroscopy is ascertaining correct balloon position and adequate vein seal without using the usual tools of fluoroscopy or contrast dye, respectively. To determine appropriate positioning of the balloon at the vein, we use ICE. A lack of color-flow Doppler in the vein indicates correct alignment of the balloon and vein. More importantly, we use hemodynamic pressure monitoring and look for a pulmonary capillary wedge waveform to confirm complete occlusion of the vein. We perform cryotherapy applications and assess for loss of pulmonary vein potentials on the recording system to indicate entrance block. We typically address the pulmonary veins in this sequence: left superior pulmonary vein, left inferior pulmonary vein, right inferior pulmonary vein, right superior pulmonary vein. For cryoablation of the right-sided pulmonary veins where phrenic nerve injury is a significant concern, the decapolar catheter is positioned at the SVC. Just prior to a cryo application, the decapolar catheter is paced at high output to capture the phrenic nerve. We monitor compound motor action potentials (CMAP) and perform tactile monitoring of right-sided diaphragmatic stimulation, ready to discontinue cryotherapy immediately in the event of diminished CMAP amplitude or diminished right-sided diaphragmatic excursion. Following cryoballoon ablation of the pulmonary veins, the circular mapping catheter is positioned in each of the veins and used to assess for exit block. Upon confirming electrical isolation, we administer isoproterenol to assess for AF inducibility. 

After my team’s initial experience with fluoroless cryoballoon ablation for AF, we have continued to employ the fluoroless technique and have performed 20 consecutive cryoballoon ablation procedures without using any fluoroscopy. Despite not performing pre-procedural CT or CMR for our patients undergoing AF ablation, we have successfully identified and performed AF ablations on patients bearing anatomical variants such as the left common pulmonary vein, right middle pulmonary vein, and even cor triatriatum sinister. The avoidance of routine pre-procedural cardiac CT has benefited the patient in terms of cumulative radiation dose. None of the patients undergoing fluoroless cryoballoon ablation have required additional focal radiofrequency or cryo applications to achieve PV isolation and AF noninducibility on isoproterenol. Thus far, of the 20 patients who have undergone fluoroless cryoballoon ablation, only 2 have recurred with AF. 

As we begin 2015, our team truly feels comfortable utilizing the fluoroless technique for this new application. As had been the experience with point-to-point ablation of AF, AVNRT, AVRT, AT, PVCs, ischemic VT, and idiopathic VT, the fluoroless procedure times have dropped significantly as our experience goes up. I anticipate procedure times, which are already comparable to conventional ablation procedures, to only decrease further in the future. 

Sharing my experience with the fluoroless approach has been a passion of mine. I believe that this approach can be learned by any operator and lab staff who possess a strong desire to eliminate the radiation risks that conventional ablation poses to patients and staff. The tools to perform a fluoroless catheter ablation can be found in nearly all U.S. EP laboratories. Our experience is proof that with the exception of arrhythmias of epicardial origin, all other tachyarrhythmias can be successfully and safely ablated using the fluoroless method. Given the long-term benefits to patients, EP lab staff, and physicians, the future of fluoroless ablation is bright. 

Disclosures: The author has no conflicts of interest to report regarding the content herein.