Atrial fibrillation, or AFib, is the most common heart rhythm abnormality. AFib occurs when the top chambers of the heart quiver or “fibrillate” instead of beating normally, often resulting in a very fast heart rate. A patient with AFib may feel heart palpitations, shortness of breath, and/or dizziness. Episodes of AFib can come and go or last for long periods. Regardless, without treatment, the ongoing abnormal heart rhythm can lead to strokes and heart failure.
The prevalence of AFib has been increasing, partly due to our aging population, as well as increased recognition of symptoms and the relationship of AFib to stroke and heart failure.
Treatment options include medications, cardioversions (using electrical signals or drugs to reset the heartbeat), a surgical maze procedure performed when the patient is already undergoing open heart surgery, and catheter ablations.
Ablation treatments modify irritable areas in the heart chamber that cause irregular heartbeats. Most patients refer to their options for catheter ablation of atrial fibrillation as “freezing” or “burning.” In fact, they are not far off. The two most common types of catheter ablation are radiofrequency ablation (“burning”) and cryoablation (“freezing”). The radiofrequency approach involves burning point-by-point, whereas the cryoablation approach uses the cryoballoon tool to freeze in a ring-shape. A recent clinical trial known as “FIRE and ICE,” on the trend of the burning versus freezing, showed the “ice” or “cryo” approach is just as safe and effective as the “fire,” radiofrequency approach to ablation.
Cryoballoon ablation is now a well-established method to treat AFib. Cryoballoon ablation is a safer, faster, and more elegant way of eliminating triggers that cause atrial fibrillation compared to the conventional point-by-point burning with radiofrequency ablation. In cryoballoon ablation, a device with a balloon attached is inserted into the heart by an operator — a doctor specializing in electrophysiology, who is an expert in heart rhythms — through a vein in the patient’s groin. When it reaches the heart, the balloon is inflated with a refrigerant that freezes tissue and stops unwanted electrical signals that contribute to AFib. While atrial fibrillation often stays away with cryoballoon ablation, we can’t consider it a “cure” because ongoing wear-and-tear caused by underlying conditions, like untreated sleep apnea or hypertension, can cause new irritable spots that can lead to recurrence.
Cryoablation has been available since 2004 in clinical trials and more widely since it was approved by the Food and Drug Administration in 2010. While cryoballoon ablation has gained significant popularity and data has emerged to prove its ability to treat AFib, every treatment has risks. Many risks can be mitigated with careful technique modifications and knowledge of dosing. Since the launch of cryoballoon ablation, new data has emerged to give us better insight on how to best dose the freezing cycle of the treatment to avoid collateral injury, such as rare but serious thermal injuries to surrounding structures, and to improve outcomes.
These insights were collected by a writing committee into a series of best practices documents for all cryoballoon operators. The best practices have been adopted as standards by many providers worldwide to ensure the procedure is consistent, safe, and effective across practices. The first Best Practice Guide explains techniques intended to reduce complications such as pulmonary vein stenosis and phrenic nerve injury. Use of the prior generation of cryoballoon focused on pushing the balloon toward high-yield areas and sealing it. After the new generation of cryoballoon was released, with a larger balloon and increased freezing power, the technique and use of the cryoballoon needed to be changed to maximize safety. By setting the standards of safety with these maneuvers, the first Best Practice Guide disseminated this safer technique worldwide to minimize potential complications.
The most recent Best Practice document addresses dosing, or how much time operators ablate tissue, in order to improve outcomes. Since the newer cryoballoon has a much larger freezing area, operators needed to modify the length of time the freezing should take place. While cryoballoon procedures have a much lower incidence of life-threatening complications compared to that of radiofrequency, appropriate dosing allowed for much safer procedures with better outcomes. This new standard of dosing has also been adopted worldwide, and cryoballoon has now been used to treat over 500,000 procedures since its release.
Like any procedure, the more the operator does it, the better the outcome, so patients considering cryoballoon ablation should look for experienced operators who keep up with the latest research and best practices to ensure optimum outcomes and safety.
Research continues to bring new treatments, as well as improved procedures for administering existing treatments. Cryoballoon ablation growth globally has been amazing. Countries such as Japan, which did not receive this new technology until 2014, now perform approximately 10,000 procedures annually. In Japan, this technology has taken over 95 percent of all AFib ablation labs. In Asia, interventional cardiologists are frequently the main operators due to a shortage of electrophysiologists in the region, demonstrating the reproducibility and safety among a wide range of operators and the benefits of establishing and sharing best practices.
As new research becomes available, a third best-practice document is being developed to address the best use of cryoballoon ablation for the treatment of patients who have lived with atrial fibrillation for long periods of time. These patients, as a result, often have a heart chamber that is more diseased, rendering ablation more complex and less reliably successful.
Wilber Su, M.D. is a cardiac electrophysiologist at Banner – University Medicine Heart Institute in Phoenix, AZ. He was lead author on “Best practice guide for cryoballoon ablation in atrial fibrillation: The compilation experience of more than 3000 procedures” (Heart Rhythm Journal, July 2015) and “Cryoballoon Best Practices II: Practical guide to procedural monitoring and dosing during atrial fibrillation ablation from the perspective of experienced users” (Heart Rhythm Journal, September 2018).