Is Cryoballoon as Effective and Safe as RF Ablation? A Clinical Study

There have been few randomization trials directly comparing CryoBalloon ablation to RF ablation.

That’s why Dr. Armin Luik and his colleagues developed the FreezeAF clinical trial―to directly compare CryoBalloon ablation to RF ablation for treating patients with paroxysmal atrial fibrillation. Dr. Luik (U. of Freiburg, Karlsruhe, Germany) presented the study results at the May 2015 meeting of the Heart Rhythm Society.

CryoBalloon catheter

FREEZEAF Trial: Patients and Method

In the FREEZEAF study, 315 paroxysmal A-Fib patients with a mean age of 60 years were randomized to either a CryoBalloon ablation (n=156) or a RF ablation (n=159) of the pulmonary veins. Clinical follow up was at three, six, nine and 12 months.

The FREEZEAF Study Results

The FreezeAF trial researchers noted that a number of CryoBalloon ablation studies have demonstrated its efficacy and safety for treatment of A-Fib, but few studies have compared the two techniques head-to-head.

How did Cryoballoon compare to RF Ablation?

• Success rates for both techniques were very similar (68% Cryoballoon vs. 65% RF).

• Cryoballoon ablations were 22 minutes faster.

• Complication were significantly higher in the CryoBalloon group than the radiofrequency group: 12.2% versus 5%; including nine in the CryoBalloon group with phrenic nerve paralysis (5.8%) with all recovered by the 12th month.

• Cryoballoon ablations also needed higher X-ray dosages to prove the balloon’s occlusion.

Regarding the study’s rate of complications, Dr Jagmeet Singh (Harvard Medical School and Mass.General Hospital) commented, “Even the absence of complications was comparable between the two…the incidence of phrenic nerve injury was higher in the cryoballoon…However, the risk for any major phrenic nerve injury was less than 2%.

Dr Jagmeet Singh

So I think the cryoballoon approach is still a very safe and efficacious procedure.”

Researchers concluded: “At both 12 and 6 month follow-ups, CryoBalloon was demonstrated to be non-inferior to RF in terms of freedom from AF in combination with an absence of persistent complications.” [What’s that mean in English? Cryo’s just as good.]

What the FREEZEAF Findings Mean to Patients

CryoBalloon as Effective as RF: The good news for patients is that CryoBalloon ablation is as effective as RF ablation. What about safety? If you discount the phrenic nerve damage as only temporary, Cryoballoon is as safe as RF. 

But there is a caveat. The Cryoballoon ablation only isolates the pulmonary veins (PVs). If you have non-PV triggers (which occur all too frequently), your electrophysiologist (EP) must map and ablate them usually using an RF point-by-point catheter. 

Sadly, some EPs aren’t able to, or won’t make this extra effort. So, be sure to ask your EP, “What do you do if I have non-PV triggers?”

Proficiency Needed by EPs

Dr. John D Day

Dr. John D. Day (Intermountain Medical Center) observed that Cryoballoon ablation is certainly easier than RF point-by-point ablation which is technically challenging and requires “many, many, many more cases” until an EP acquires a mastery of the RF point-by-point technique.

Chair of the 2015 HRS session, Dr. John Mandrola, agreed. “The challenge of PVI with RF energy is that it’s tough making lines with dots. The hand-eye-brain neural pathways that guide point-by-point catheter manipulation in the LA [left atrium] take years to form. It’s not easy. Quality RF ablation comes from hard-won human skills.”

Why One EP Chooses to Use CryoBalloon Over RF for Ablations

Dr. John Mandrola lists the reasons why he uses the Cryoballoon Ablation procedure:

Dr. John Mandrola

• “Cryoballoon [isolation] distorts the cellular matrix less than RF. The histology [microscopic anatomy of cells/tissues] of a Cryo lesion is much cleaner than that of RF.” If you look at a Cryoballoon freeze, the frozen heart tissue looks somewhat normal, whereas RF burns are real scars.

• Cryoballoon ablation is easier to do. A single circular freeze can isolate a vein rather than many RF point-by-point lesions. Though Cryoballoon ablations can also have gaps and recurrence like RF.

• Cryo-formed freeze lines might be more durable and therefore decrease the need for redo procedures. Some studies have shown a slight superiority of Cryo. But much more research needs to be done to confirm this.

• Preservation of left atrium function. Cryoballoon makes discrete circular lesions close to the PV―away from the left atrium proper. “What good is sinus rhythm if the atria do not squeeze [properly]?”

• Decreased risk of macro-reentrant flutters [from gaps]. After Cryoballoon ablation, there seems to be fewer macro-reentrant arrhythmias which are highly symptomatic and tough to treat.

• Safety. “…many experts argue that Cryo is safer than RF.” But we need more head-to-head randomized control trails on this subject.

Dr. Mandrola concludes, “These are the reasons that compelled me to learn CryoBalloon ablation. It passed the Mandrola [my] test: I’d consider having it done on myself.”

More about CryoBalloon Ablation

Preserving Left Atrial Function: If you run, cycle, swim, etc., you should be concerned about preserving left atrial function. Certain RF ablation strategies such as wide area antrum isolation make oval burns around two pulmonary veins (PVs). The resulting scarring may significantly affect part of the left atrium further away from the PVs.

Cryoballoon freezes the heart tissue and looks somewhat normal, whereas RF burns are real scars.

Any RF burn area in the left atrium is forever dead, fibrotic, immobile and has no blood flow or transport function. These RF burns and scarring may make the heart stiffer and possibly decrease contractile function. But I don’t know of any studies which have examined how much the heart is affected by these burn scars. How will this permanent scarring affect heart function over the long term, we just don’t know.

Monitoring the Phrenic Nerve: In the FREEZEAF study, of the 156 CryoAblation patients, nine had the complication of phrenic nerve paralysis (5.8 %); no paralysis lasted longer than 12 months, and six of the nine recovered before the six-month follow-up.

To avoid phrenic nerve damage, most EPs now monitor the phrenic nerve during a Cryoballoon ablation. If the phrenic nerve is affected, they simply stop the Cryoballoon ablation in that area. A Cryo freeze isn’t immediately permanent and irreversible (unlike an RF burn). As the tissue defrosts, it usually returns to its normal function.

When you are interviewing an EP to perform your Cryoballoon ablation, ask them, “How do you protect my phrenic nerve?”

The Bottom Line—What Counts is the Skill and Experience of the EP

When researching and selecting an EP, what’s most important is their skill, experience, and demonstrated results, not what energy source they use for the ablation.

Many of the “Master” EPs still use RF point-by-point ablation which works for them. Objectively, Cryoballoon is probably better than RF, all things considered. But that doesn’t really matter.

What you need is the best, most experienced EP you can find, regardless of what energy source they use for your ablation.