As medical procedures improve and technology advances, there is an increasing awareness of the need to limit (or eliminate) unnecessary radiation exposure. The recent 2014 Scientific Statement from the American Heart Association examined this issue and proffered recommendations.1 That report cited the 2009 National Council on Radiation Protection & Measurements’ report that the total radiation exposure to the U.S. population from medical imaging has increased six-fold since 1980, and that nearly 40% of this medical radiation exposure to the U.S. population (excluding radiotherapy) is related to cardiovascular imaging and intervention.2 Our center has made a conscientious effort since 2010 to integrate multiple modalities into our EP studies and ablations, with the express purpose of reducing fluoroscopy use. Upon this background, we began using the Arctic Front cryoablation system (Medtronic, Inc.) in August 2011. Within six months of first using the system, we were able to cut fluoroscopy use by >90%. Since then, we have reduced fluoroscopy for pulmonary vein isolation (PVI) procedures using the Arctic Front system to one minute or less; use is primarily limited to the transseptal puncture. To illustrate how this is accomplished, this case study presents a recent patient who successfully underwent PVI using Arctic Front.
This is an 82-year-old male who first presented in October 2014 with paroxysmal atrial fibrillation (PAF) to the consult service. The PAF was first diagnosed in rehabilitation after orthopedic surgery. Over the next two months, the patient required two cardioversions, even after starting daily flecainide, for recurrent PAF. In January 2015, he elected to undergo pulmonary vein isolation at our center using the Arctic Front cryoablation system (Medtronic, Inc.). After a pre-ablation transoesophageal echocardiogram (TEE), the patient was prepped and bilateral femoral vein access was obtained using ultrasound guidance to avoid vascular injury. Two sheaths were placed in each vein. A 20-pole duodecapolar diagnostic catheter was placed in the right atrium with the distal tip in the coronary sinus, and a deflectable octapolar catheter was placed in the His bundle position. Next, a long 8 French RAMP sheath (St. Jude Medical) and 8 mm ablation catheter were placed in the right atrium. All catheters and sheaths were placed without fluoroscopy, using only the EnSite NavX mapping system (St. Jude Medical). After a cavotricuspid isthmus ablation was performed (without fluoroscopy), an intracardiac echo (ICE) probe was placed in the right atrium and a successful, single transseptal puncture was performed using minimal fluoroscopy and direct visualization with ICE. The transseptal needle was removed from the SL1 sheath and, using NavX mapping and ICE, a long Storq wire (Cordis Corporation) was easily advanced into the left superior pulmonary vein. Position was confirmed using single shots of fluoroscopy, and the SL1 sheath was removed and replaced with a FlexCath deflectable transseptal sheath. Through this, a 28 mm Advance balloon and Achieve catheter (Medtronic) were introduced into the left atrium. Using ICE imaging, NavX mapping, and pressure tracings obtained from the distal tip of the balloon to confirm vein occlusion, all five pulmonary veins were successfully isolated without the use of contrast. Total procedure time: 150 minutes. Total fluoroscopy time: 0.6 minutes. Total radiation exposure: 21 air kerma. Total contrast used: 0 cc. At this point the procedure was terminated, and there were no complications. The patient had been fully heparinized during the case and, after post-procedure protamine was given, sheaths were removed and the patient was transferred to the recovery area. He was monitored overnight and discharged the next morning on three weeks of rivaroxaban and three months of flecainide.
The Arctic Front cryoablation balloon was first approved for use in the United States in early 2011 as an alternative to radiofrequency ablation for pulmonary vein isolation. The first generation included a single, narrow band 28 mm balloon and deflectable sheath (with limited maneuverability). The procedure involved performing multiple contrast injections prior to each freezing application to confirm vein occlusion. Confirmation of vein isolation required mapping and remapping each vein before and after freezes using a separate lasso catheter, and often required two transseptal punctures. Our center adopted the Arctic Front in August 2011. The first nine cases were six to eight hours in duration, and required up to 40 minutes of fluoroscopy. Because of the difficulty isolating the right inferior vein, “clean-up” with a radiofrequency ablator was often necessary. By the tenth case, I began making significant improvements through a conscientious effort to simplify the procedure and eliminate unnecessary steps. This included replacing contrast injections with the use of pressure tracings and limiting fluoroscopy through the use of ICE and NavX mapping. These changes, along with the subsequent introduction of the newer generation Advance balloons (with a wider band for a larger area of contact and a smaller 23 mm balloon), a new and more deflectable Medtronic FlexCath steerable sheath (with a greater range of flexibility), and a through-the-lumen Achieve lasso diagnostic catheter, resulted in the reduction of both procedure times and fluoroscopy exposure along with a concomitant rise in the rate of successful vein isolation. As of January 2015, my average procedure time (including TEE) is under three hours. We now document 100% acute isolation of all pulmonary veins (including common left and right pulmonary veins) during the case without the use of “touch up” radiofrequency ablation. For all 56 cases that I performed in 2014, the average fluoroscopy time was 1.0 minute (range 0.2 to 5.4 minutes for one complicated case), and the total air kerma for all cases was 27.4 Gray. I have not had a single procedural complication in over a year (the last was pericardial effusion and pericardial tamponade). In three and a half years, I have documented four cases of transient phrenic nerve palsy (lasting from a few minutes to a few months). No CVA, pulmonary vein stenosis, major bleeding events or death have occurred.
The current generation of the Arctic Front balloon, Achieve catheter, and FlexCath sheath, in combination with ICE, pressure tracings, and 3D mapping, can be safely used to achieve a high rate of pulmonary vein isolation, minimal fluoroscopy use, and short procedure times without compromising patient safety. At our center, Arctic Front is a fast, safe and effective tool for treatment of paroxysmal atrial fibrillation.
- Fazel R, Gerber TC, Balter S, et al. Approaches to enhancing radiation safety in cardiovascular imaging: a scientific statement from the American Heart Association. Circulation. 2014;130(19):1730-1748.
- National Council on Radiation Protection & Measurements. Ionizing Radiation Exposure of the Population of the United States. Bethesda, MD: National Council on Radiation Protection & Measurements; March 2009. NCRP Report No. 160.