Balloon catheters can ablate larger areas of tissue than traditional, single-point catheters that require point-by-point ablation. Balloon catheters typically perform pulmonary vein isolation for paroxysmal atrial fibrillation, but treatment for those with persistent afib is now possible, too.
After inserting the balloon catheter, the electrophysiologist inflates the balloon and delivers cryo, laser, or radiofrequency energy. EPs don’t need expensive real-time mapping systems with balloon catheters, which could put catheter ablation within reach of any facility with electrophysiology equipment.
In addition, balloon catheters could decrease ablation time since a large area of tissue can be ablated simultaneously. Shorter ablation time means less exposure to radiation from fluoroscopy. However, the time needed to perform ablation varies by EP. In general, those with the most experience are faster and have higher success rates than those with limited ablation experience.
Balloon-based systems may improve success rates and lower the procedure time. However, it can be challenging to position some balloon catheters in the right-sided pulmonary veins. If the balloon is positioned too deeply, pulmonary vein stenosis could develop. In addition, some balloon catheters have difficulty reaching the right inferior pulmonary vein, so the EP may need to use a single-point catheter to ablate this vein.
We’ll look at cryoballoon, laser balloon, and radiofrequency balloon catheters.
The ArcticFront™ Cardiac Cryoablation System (Medtronic) uses nitrous oxide gas cryo energy to ablate tissue by freezing it. The included Arctic Front balloon catheter has two balloon sizes (23mm and 28mm) to accommodate different pulmonary vein sizes. Each balloon is actually composed of two balloons. Nitrous oxide gas is delivered to the inner balloon. The outer balloon is a safety cushion, so the gas doesn’t directly contact heart tissue. After positioning the catheter in the pulmonary vein, the EP inflates the balloon and delivers the cryo energy to the balloon.
The EP may use a single-point cryo-catheter similar to traditional radiofrequency catheters to make additional lesion lines or perform “touch-ups.” In addition, a mapping catheter is typically used in procedures to confirm that pulmonary vein isolation has been achieved.
The Arctic Front cryoballoon received European regulatory approval in 2005 and has been used to treat hundreds of thousands of patients worldwide since it was first introduced. In December 2010, Arctic Front became the first balloon catheter to receive FDA approval for afib treatment in the US.
In the STOP AF study in the US, Arctic Front did better than antiarrhythmic medication in stopping atrial fibrillation in patients with paroxysmal afib. One year after the procedure, 58% of those with cryoablation were free from afib and could stop antiarrhythmic drugs. Overall, 69.9% were afib-free, but some stayed on antiarrhythmic drugs. Comparatively, 7.3% of patients who only took antiarrhythmic drugs were free of afib at one year.1
Individuals with an Arctic Front ablation also had fewer complications, with a major adverse event rate of only 3.1% compared with 8.5% for patients who took antiarrhythmic drugs. However, there was one stroke related to the procedure, and seven patients developed pulmonary vein stenosis. Some people who had cryoablation suffered from phrenic nerve injury, a severe complication that makes it difficult to breathe normally. Most of the 29 phrenic nerve injuries were resolved within three months. Nearly all had stopped after 12 months without needing another procedure.
The rate of phrenic nerve damage may have been related to the learning curve, an EP’s experience with the Arctic Front cryoballoon. EPs are used to placing and manipulating single-point radiofrequency catheters, but balloon catheters are newer. At the 2011 Boston Atrial Fibrillation Symposium, conference organizer and STOP AF investigator Dr. Jeremy Ruskin presented data showing how the learning curve affected STOP AF success and safety. For example, doctors who had performed 12–23 cryoablation cases had higher success rates than those who had completed only one or two procedures. Similarly, there were no major adverse events when the procedure was performed by an experienced operator compared to a 7% rate for those doing it for the first time.
As EPs became more familiar with the cryoballoon, the incidence of phrenic nerve injury decreased. Dr. Ruskin reported that the incidence of phrenic nerve damage was halved in the 80 patients who received cryoablation after the official trial. Procedure times improved as well. The average procedure time was six hours in STOP AF, with experienced doctors having lower procedure times than less experienced doctors. However, the average ablation and fluoroscopy time was just over an hour, which underscores how quickly a balloon catheter can ablate a large area of tissue.
Patients who had an Arctic Front cryoballoon ablation reported a vast improvement in quality of life. Individuals participating in the STOP AF trial completed a questionnaire on symptoms before the procedure and one year after it. Before treatment, all patients had afib symptoms, such as palpitations, fatigue, and shortness of breath. One year after the procedure, only 20% of patients reported having symptoms. See how Arctic Front improved patients’ lives.
In 2012, the Arctic Front Advance Cardiac Cryoablation Catheter, the second generation Arctic Front Catheter, received US FDA approval to treat paroxysmal atrial fibrillation. In contrast to the first generation, the Arctic Front Advance Cardiac Cryoablation Catheter features technology that optimizes the delivery of the coolant inside the balloon. This allows for a more uniform cold surface and reduces the effort needed to isolate the pulmonary veins, potentially reducing procedure times.
In 2015, the US FDA approved the third generation Arctic Front Catheter to treat paroxysmal afib patients for whom medications didn’t work. This catheter has a 40% shorter tip than the Arctic Front Advance Cardiac Cryoablation Catheter to help EPs see the procedure in real-time and increase catheter maneuverability.
The third-generation Arctic Front Advance Catheter has been investigated in patients with persistent afib. In the CRYO4PERSISTENT AF study, 61% of persistent afib patients were free from all arrhythmias lasting more than 30 seconds one year after ablation with the Arctic Front Advance Catheter.2
The STOP PERSISTENT AF study examined the Arctic Front Advance and the Freezor Max cardiac cryoablation catheter to treat persistent afib, which is harder to treat. In this trial, conducted at 25 sites in Canada, Japan, and the US, the success rate (freedom from afib and other atrial arrhythmias) at 12 months was 54.8%. There was one safety event (0.6%), and the patient recovered in a month. Quality of life was significantly improved for most participants.3
Based on this study, the FDA granted approval for the Arctic Front Advance Catheter to treat those with persistent afib, making it the first ablation catheter approved in the US for this use.
The STOP AF FIRST trial examined the safety and effectiveness of the Arctic Front Advance Cardiac CryoAblation Catheter for the treatment of reoccurring symptomatic paroxysmal afib in those who had not taken antiarrhythmic drugs. In this US trial, 104 patients received ablation, and 99 received antiarrhythmic drugs. Following rigorous 12-month monitoring, the success rate was 74.6% for cryoballoon ablation and 45% for antiarrhythmic drugs. The complication rate was 1.9%, with only two safety events, pericardial effusion and a heart attack.4
The HeartLight Endoscopic Ablation System (CardioFocus), which is approved in the US, Europe, and Japan, uses laser energy to ablate tissue. In addition, the laser balloon offers real-time visualization, meaning the EP can see where the balloon is positioned and where the energy is delivered.
Doctors who spoke about their experience with the laser balloon at a Heart Rhythm Society meeting said its visualization capability is a significant step forward for catheter ablation. Dr. Moussa Mansour of Massachusetts General Hospital reiterated the importance of this feature at the Boston Atrial Fibrillation Symposium. He stated that real-time visualization becomes more critical when a patient has a complex anatomy. In addition, he noted two other advantages: doctors can see whether there are any gaps in the ablation lines, which could increase effectiveness, and they also can see when tissue starts to overheat and adjust the power accordingly, which may reduce some complications.
The laser balloon is made of a unique material that allows it to conform to various pulmonary vein sizes and shapes. Inside the balloon are an endoscope (miniature camera), an optical fiber to deliver laser energy, and a lumen (small tube) to circulate liquid coolant. The endoscope enables the EP to see balloon placement and where the laser energy is delivered. The EP positions the catheter at the ostia (opening) of a pulmonary vein, inflates the balloon, and then delivers the laser energy, which is visible as a green light, to create lesions. When one area has been ablated, the doctor turns the balloon to ablate another area.
Advanced mapping systems aren’t needed for this procedure, but intracardiac echocardiography (ICE) is typically used to provide real-time ultrasound images. A mapping catheter is also used to confirm that the pulmonary veins have been isolated.
In the US pivotal clinical study of the HeartLight System, 353 paroxysmal afib patients who could not tolerate or failed to respond to antiarrhythmic drugs were randomized at 19 centers. They received pulmonary vein isolation using either the HeartLight System or standard irrigated radiofrequency ablation. One-year results from the trial showed that with a single ablation procedure using the HeartLight System, 61% of patients experienced freedom from afib. The HeartLight System performed similarly to radiofrequency ablation. Twelve percent of those receiving ablation with the HeartLight System had adverse events compared to 15% in those who had irrigated radiofrequency ablation. This was mainly driven by cardioversions.5
A newer version of the HeartLight System is currently under study.
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Radiofrequency balloon catheters are being investigated for the treatment of atrial fibrillation. These catheters combine the benefits of single-point radiofrequency ablation and balloon-based approaches and have the ability to deliver different levels of energy in short procedure times. Recent trials investigating radiofrequency balloon catheters provide promising evidence supporting their use. However, there is a need for large, randomized studies
HELIOSTAR (Biosense Webster) is a multielectrode radiofrequency balloon catheter with ten irrigated, flexible, gold surface electrodes that independently deliver varying amounts of power. The ability to deliver different energy levels may prevent deeper ablation to surrounding tissue and allow operators to directionally tailor the energy delivery. The radiofrequency balloon catheter is designed to be safe and effective while also reducing procedure time.
The RADIANCE study, a multicenter feasibility study in Europe, included 39 patients who underwent catheter ablation using the HELIOSTAR catheter. All treated pulmonary veins were electrically isolated without the need for additional touchups. After 12 months, 75.7% of patients were free of afib and other arrhythmias and off antiarrhythmic drugs. Procedure-related adverse events included phrenic nerve injury in one patient.6
In the US, the STELLAR Study will take place soon.
Luminize (Boston Scientific), previously called Apama, is a radiofrequency balloon catheter. It is a multielectrode circular balloon catheter. The built-in digital cameras with LED lights and sensing electrodes on the balloon enable real-time visualization of electrode contact with the tissue during ablation.
In the multicenter AF-FICIENT pilot study, there was a high success rate with no severe complications.7 However, the future is not clear due to the recent withdrawal by the sponsor of a proposed study.
The SATAKE HotBalloon® (Toray) is another balloon catheter that uses radiofrequency energy. It was developed by Dr. Shutaro Satake in Japan and approved for use in Japan in 2015. The balloon is made of a compliant material that can conform to various pulmonary vein sizes and shapes. It is filled with a solution of saline and an ionized contrast medium. Inside the balloon, there is a coil electrode, the source of radiofrequency energy, and a thermocouple to measure temperature. When the radiofrequency energy is delivered to the balloon, the coil electrode gets hot. The balloon has an agitation system that constantly mixes the saline solution and keeps the entire balloon at a single temperature to reduce charring.
The balloon’s malleable material helps to identify when a complication could arise. For instance, by looking at how the balloon’s shape changes at the pulmonary veins, EPs can withdraw the balloon when inserted too deeply, thus avoiding pulmonary vein stenosis. Similarly, by watching the shape of the balloon, EPs can avoid damage to the esophagus. Using a pacing device near the right superior pulmonary vein can prevent damage to the right phrenic nerve, one of the nerves making the diaphragm contract automatically during breathing.
Dr. Satake and his colleagues have published initial and long-term HotBalloon ablation results. In the feasibility study8 of 63 paroxysmal and 37 persistent patients, patients received antrum pulmonary vein ablation as well as ablation of the roof and posterior (back) wall of the left atrium. The complication rate was low, and there were no cases of severe pulmonary vein stenosis. However, three people (3%) had asymptomatic pulmonary vein stenosis, and one had phrenic nerve injury.
The single-center study showed very high success rates. At 11 months, 60 (95%) paroxysmal patients and 32 (86%) persistent patients were free from afib and off antiarrhythmic drugs. Follow-up monitoring started three months after the ablation, with patients instructed to use a mobile ECG (electrocardiogram) at the same time each day for three months. In addition, they were to activate the ECG when experiencing afib. Despite this rigorous monitoring, asymptomatic afib may have been missed. In addition, the authors didn’t define freedom from afib, so we can’t judge this high success rate.
Long-term results over 6.2 years of follow-up in 238 paroxysmal afib patients who were ablated showed 64.7% freedom from afib without antiarrhythmic drugs. There were four cases (1.7%) of pulmonary vein stenosis and eight cases (3.4%) of phrenic nerve injury. However, all phrenic nerve cases resolved within three months.9
Recently, results were published from the post-approval study from 46 sites in Japan. Of 491 afib patients, 94.1% were afib-free at 24 weeks and 87.8% at 48 weeks. The overall adverse event rate was 21.5% but was 2.6% for ablation-related adverse events, with pericardial effusion (fluid on the lungs) being the most common.10
To find out about other tools used in catheter ablation procedures, see Mapping and Navigation Tools, Electroanatomic Mapping Systems, and Robotic Catheter Navigation.
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