John Mandrola


June 22, 2015

On the day I left for the European Heart Rhythm Association Sessions in Milan, Italy, a patient with atrial fibrillation emailed me to ask about the benefits of focal impulse and rotor modulation (FIRM) ablation with the Topera (Abbott) system. It is not the first time a patient has asked whether they should travel to a site that does rotor ablation.

In 2014, Abbott Labs acquired Topera in a deal valued at close to $250 million according to the Wall Street Journal. That kind of money buys attention. Electrophysiologists in the United States are increasingly asking administrators to invest in the technology. American patients, too, are wondering.

In brief, the story of FIRM ablation is one that took the world of electrophysiology by storm in 2012. I was in the packed conference room when the eminent Dr Warren Jackman (Oklahoma University, Oklahoma City) came to the mike and said, "This could turn the world of AF ablation upside down." That was then. That was in the United States.

No one mistakes Milan for Orlando. The differences between Europe and the United States are many. Take cardiology: in the case of left atrial appendage occlusion, renal denervation, and transcatheter aortic-valve replacement, European physicians jumped in well before Americans. Yet that frontier spirit has not occurred with rotor-guided AF ablation. Europeans are slow to embrace the novel computational (and somewhat mysterious) means to seek and destroy drivers of a disease afflicting millions.

I was once a hopeful enthusiast of this technology. It's harder to remain that way now. Recent data, including abstracts and posters from day 1 at the EHRA sessions, were neither hopeful nor enthusiastic regarding FIRM ablation.

Dr Roland Tilz (Asklepios Clinic, Hamburg, Germany) presented 13-month follow-up of 25 patients with paroxysmal or persistent AF ablated with FIRM guidance before standard pulmonary vein isolation (PVI).[1] Before I tell you what he said, make note of the number of patients treated with this technique at one of the busiest ablation centers in Europe—just 25.

Tilz reported termination or slowing of AF at rotor sites in 50% of cases. Procedure time averaged 235 minutes. AF recurred in 25% of patients at 1 year. He called his team's findings in line with previous studies. In the Q&A session, he began an answer with the word "Honestly." At medical meetings, that's a cue to pay attention.

"Rotor ablation is new. It's a different concept. As research, this is fascinating. But it is not the standard of care. We need clinical trials; we need data."

In a "best-abstracts" poster session, Dr Pawel Kutlik (Maastricht University, the Netherlands) reported on the technical challenges of identifying rotors during atrial fibrillation.[2] They mapped the atria by two means—either endocardially with a typical basket catheter (n=19) or epicardially with high-density electrode arrays placed at the time of cardiac surgery (n=12).

They found a typical basket catheter covered only 46% of the atria; a high probability of rotor detection due to chance; a short lifespan of rotors; and poor specificity of rotor detection. They concluded that rotor detection depends on the implemented algorithm, especially the number of electrodes used to detect the phase singularities.

These findings, from a center famous for cardiac mapping, gives credence to one of the main arguments cited by skeptical European doctors—that the secret sauce, the black box of Topera, is a flawed algorithm.

In another abstract ,[3] Dr Anja Schade (HELIOS Klinikum Erfurt, Germany) and colleagues took the FIRM challenge to its maximum. They tried ablating patients with persistent AF with FIRM alone—no PVI. In 21 mostly male patients (mean age 62), they found an average of one RA rotor and three (+1–4) in the left atrium. No patient had successful AF termination. Slowing of cycling length occurred in 10 of 21 patients and two of 21 converted to atrial tachycardia. Procedure times averaged 227 min. Complications were low. But early recurrences were noted in 67% of patients.

They concluded that FIRM ablation appeared safe in terms of procedural complications, such as esophageal lesions and asymptomatic cerebral lesions, but success rates without PVI were suboptimal.

To be fair, a group of US investigators, led by Dr DE Krummen (Veterans Affairs San Diego Healthcare System, CA) presented good 30-day safety data on 325 FIRM-PVI and 300 PVI-alone controls.[4] These cases were done at seven US centers and the overall complication in both groups was not significantly different at 3.7% (PVI+FIRM) and 2.7% (PVI-alone). Each group had one stroke, one heart block, and very similar hospitalizations. Six patients in the PVI+FIRM group had pericardial effusion compared with only one with PVI alone—a numerical difference that did not reach statistical significance.

Perhaps most damning for FIRM ablation was a recent paper published in Circulation Arrhythmia and Electrophysiology by the UCLA group of Drs Roderick Tung and Kalyanam Shivkumar—who were part of the original team of researchers doing FIRM. They reported their experience in 24 patients who underwent FIRM-guided AF ablation.[5] They found rotors in each patient, but the acute procedural end point (AF termination or AF slowing) was achieved in only half the patients. When they studied the signals offline, they noted no differences between rotor and distant sites in dominant frequency or Shannon entropy. Electroanatomic mapping showed no rotational activation at FIRM-identified rotor sites in 23 of 24 patients. The respected investigators concluded that putative rotor sites did not look like rotors, nor did they look different from adjacent sites.

In the accompanying editorial,[5] Drs Walters and Kalman (Royal Melbourne Hospital, Australia) say, "The lack of distinguishing electrogram features at the putative site of focal drivers such as rotors is a striking finding." In the concluding paragraph, they note that until the randomized clinical trial Substrate and Trigger Ablation for Reduction of Atrial Fibrillation 2 (STAR AF) was done, it wasn't known that an accepted technique—ablation of complex fractionated atrial electrograms and linear lines—was not useful and probably harmful. This reversal, they argue, speaks to the need to better understand AF mechanisms. "On available evidence," they write, "the relative contribution of sustained or transient rotors, of focal drivers, and of multiple wavelets to the mechanism of human persistent AF remains uncertain."

So to answer my patient's question, I think it is fair to say the benefits of FIRM ablation are decidedly undecided.



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