FAST Trial: Surgical Versus Catheter Ablation―Flawed Study, But Important Results for Patients

By Steve S. Ryan, PhD
December 29, 2011

Not that long ago, surgery was the only way to fix most heart problems including Atrial Fibrillation (the Cox-Maze operation). But thanks to new techniques and discoveries like stents and the Bordeaux Group’s discovery in 1994 that a catheter with an electrode at the end can electrically isolate the pulmonary vein openings making people A-Fib free, electrophysiologists (EPs) became more involved in fixing heart problems. Surgeons had less to do.

The last fifteen years saw a tremendous growth in the number, training and quality of EPs doing Pulmonary Vein Isolations (PVIs). I remember when I could find and list only ten centers doing PVIs. Now there are over a thousand in the US alone. A-Fib is indeed an epidemic, but the medical field has risen to the challenge. Few medical discoveries have been introduced and received such wide-spread acceptance in such a short time as catheter ablation (PVI).

FDA Approves AtriCure Synergy Ablation System

And recently surgeons have gotten back in the game, thanks in no small part to the work of AtriCure, Inc. whose Synergy Ablation System was recently approved by the FDA (December 16, 2011). (The FDA approved the AtriCure system “in patients who have persistent or longstanding persistent Atrial Fibrillation and are also undergoing surgery for coronary artery bypass grafting or valve repair or replacement.” The AtriCure System is and can still be used off-label for paroxysmal A-Fib. It’s probably only a matter of time before the FDA approves AtriCure’s System for paroxysmal, stand-alone operations such as the Wolf Mini-Maze.)

The FDA approval, though limited, is nevertheless a major medical breakthrough for A-Fib patients. A-Fib patients now officially have a choice of treatments.

Catheter or Surgical Ablation?

 But which is better—catheter or surgical ablation? Over the years there have been many multi-center studies and data developed about the efficacy and safety of catheter ablation. But that’s not the case for the AtriCure system which is a relatively new treatment.

For what is probably the first time, a recent small study compared the two treatments head-to-head. AtriCure, Inc. provided funding for the study “Atrial Fibrillation Catheter Ablation Versus Surgical Ablation Treatment (FAST).” 59 patients at St. Antonius Hopital in Nieuwegein, the Netherlands and 64 patients at the Hopital Clinic in Barcelona, Spain were randomized to receive either a catheter ablation (CA) or surgical ablation (SA). Patients were selected who had a prior failed catheter ablation (67%), had a left atrium diameter of 40 to 44 mm and hypertension (28-40 mm is normal), or a left atrium diameter greater than 45 (33%). (At first glance this seems like stacking the deck against a successful catheter ablation. These are more difficult cases requiring more than a simple Pulmonary Vein Isolation ablation.)

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Catheter Ablation

At St. Antonius Hospital the Pulmonary Veins were re-isolated. No additional lines or ablation strategies were performed regardless of the type of A-Fib. A non-irrigated tip RF catheter was used. (This is surprising as non-irrigated tip catheters are outdated and considered less effective. Irrigated-tip catheters are SOP (Standard Operating Procedure) in most A-Fib centers today.)

At the Hospital Clinic an irrigated tip RF catheter was used. An additional Left Atrium roofline could be made at the discretion of the operator. Sometimes a Mitral Isthmus line was also made.

At either site no mention was made of using current mapping strategies to find and isolate activation sites, or the use of Complex Fractionated Atrial Electrograms, or Dominant Frequency, or step-wise ablation protocols typically used in more complex cases. (See 2007 Boston AF/Bordeaux 5-Step Ablation Treatment for Chronic A-Fib.) According to the study authors, “patients in the CA group may have been undertreated compared with patients in the SA group.” “More than 40% of (the CA) patients had nonparoxysmal AF and may have been undertreated by PVI alone…67% had already failed a prior CA, which may be a more serious predisposition to failure than anticipated.”

Surgical Ablation: AtriCure Synergy Ablation System

The surgical ablation arm used the AtriCure Synergy Ablation System which uses an RF clamp to ablate and isolate the pulmonary veins. In addition, 31% of patients had various additional LA ablation lines at the LA roof, aortic trigone, mitral isthmus, or box lesion around the PVs. “Part of these lines were made without verifying that conduction block had indeed been established.” (In a somewhat surprising observation, the authors concluded “efficacy tended to be a little lower in patients with such lines.”) The Left Atrial Appendage was also removed. And Ganglia areas on the outside of the heart were also ablated. 

Editor’s comment: Ganglia Ablation is a subject of some controversy that deserves its own report. There are over 1000 neurons (nerve signal pathways) in the Ganglia areas. They affect other areas than just A-Fib, such as the ventricles and the GI tract. According to the authors of this study, “So far, no randomized clinical trials have quantified the added effect of surgical ganglia ablation to achieve freedom from AF.”

FAST Study Results

Efficacy: (As one would expect), the efficacy of catheter ablation was low—44.4%. What was more surprising was that the efficacy of Surgical Ablation was only 67.2%, far less than the over 90% success rates often reported (in unpublished, self-reported, or single-center, non-controlled series with short duration and lax follow-up). This is all the more surprising in that the surgical arm, in addition to isolating the pulmonary veins, often employed additional extensive lesion sets and burns in the left atrium and elsewhere on the heart. Whereas the catheter ablation arm was limited in ablation strategies it used.

Safety: The procedural adverse event rate for surgery was 23% (approximately 1 out of 4 patients) which was significantly higher than catheter ablation 3.2% (in line with previously published data). The main procedural complications in surgery were pneumothorax (collapsed lung), major bleeding, and the need for a pacemaker. (In surgical ablation the lungs have to be alternately deflated and re-inflated to fit the clamp around the pulmonary veins. Especially in older people whose lungs are no longer as elastic, this may be hard on the lungs.) These complications were caused “mostly from direct mechanical injury during the procedure. About half required additional intervention and/or prolonged hospitalization.”

“The events reported with CA seemed more transient and did not require intervention.” They seemed to center around anticoagulation, with bleeding on the one hand and transient ischemic attack, stroke and hemorrhage stroke on the other. (One of the CA patients died of a hemorrhagic stroke a month after the ablation.)

Catheter Ablation procedure time was shorter, on average 163 minutes versus a Surgical Ablation average of 188 minutes. CA patients tended to stay in the hospital 2.0 days, versus 5.5 days for surgery.

Unlike catheter ablation, “there are no large registries for minimally invasive surgical ablation that provide good insight into safety.”

Editor’s Comments: Though not the fault of the study’s investigators, the deck was obviously stacked against catheter ablation. The success rates were far lower than previously published and documented data. (For example, the Bordeaux Group reports a 95% success rate after two ablations using their step-wise ablation protocol for Persistent A-Fib patients.) But what was more surprising was the moderate success rate for the surgical arm which seemed to pull out all the stops and use the newest, most advanced extensive lesion sets and burns to achieve success.

In terms of safety, a nearly 1-in-4 major adverse event rate is huge when one considers that the surgeons were probably under intense scrutiny to perform their best and not make any mistakes, since so much was riding on this study.

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What the FAST Study means for Patients

This was probably the first study to provide documented, verifiable, non-self reporting data on the safety of Surgical Ablation (Mini-Maze). The results for patients were not good. A 1-in-4 chance of a major adverse event is not acceptable for most patients.

This study did not address simpler cases of Paroxysmal A-Fib. But the surgical Mini-Maze operations are generally the same for Paroxysmal as for more complex cases. Until we get verifiable data to the contrary, anyone going for a Mini-Maze operation should expect a 1-in-4 chance of a major adverse event.

“But what if I’ve had a failed catheter ablation? Shouldn’t I get one of the more advanced types of Mini-Maze ablations?” A 67% success rate is certainly acceptable and is better odds than you’d get in Las Vegas. But one of the more disturbing findings in this study is that with the more advanced surgical approaches using ablation lines on the left atrium and burns on other areas of the heart, “efficacy tended to be a little lower in patients with such lines.” The Mini-Maze operations featuring extensive ablation lines and burns didn’t seem to work, at least in this study.

And according to the numbers, you have a better (and much safer) chance of being A-Fib free if you go to catheter ablation centers specializing in advanced activation mapping, step-wise protocols, etc. Unfortunately those centers are relatively few and far between. The Bordeaux protocol, for example, is currently used in only a few centers around the world. And catheter ablation strategies for complex cases currently have not been standardized, though most centers’ strategies are very similar (See Comparison of Dr. Pappone’s, Haïssaguerre’s and Reddy’s Stepwise Approaches in Ablating for Chronic A-Fib). The FAST study, though probably the first of its kind, was a relatively small study. A-Fib patients shouldn’t rely entirely on the results of this study for their medical decisions. While the efficacy results for catheter ablation should probably be discounted because of the design bias of the study, the FAST study does raise red flags particularly about the safety, but also about the efficacy, of surgical ablation (Mini-Maze) operations.

Most reports of the FAST study tout the higher success rate of surgical versus catheter ablation, but these results don’t hold up under close scrutiny. More important for patients is the high complication rate and safety of surgical ablation.

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Last updated: Tuesday, June 12, 2018