New AF mapping technology data may finally silence the skeptics

By Larry Haimovitch

Medical Device Daily Contributing Writer

May 15, 2012

BOSTON — "Maybe there is some real benefit here," is hardly a ringing endorsement for an emerging medical technology. However, relative to just a year ago when the near unanimous sentiment regarding a new atrial fibrillation (AF) technology was heavy skepticism ("this sounds way too good to be true"), it would seem that some major progress has been made.

Indeed, the AF mapping and ablation technology being developed by privately-owned Topera Medical (Lexington, Massachusetts), was one of the shining lights of this year's annual scientific sessions of the Heart Rhythm Society (HRS; Washington), which was held here late last week.

Topera debuted at last year's HRS with virtually no advance fanfare and reported very promising results from its Conventional Ablation for Atrial Fibrillation With Or Without Focal Impulse and Rotor Modulation (CONFIRM) trial. CONFIRM provided enough benefit to warrant further investigation and consideration by the highly skeptical, "show me" electrophysiologist (EP) community.

Last year's "too good to be true" reaction from EPs who are the undisputed experts in diagnosing and treating AF, was understandable. The trial began in late 2005, the small amount of data were derived from just one clinical site and were generated by a relatively unknown EP physician, Sanjiv Narayan, MD, from the University of California San Diego. Dr. Narayan spent about a decade working in relative obscurity on this technology with grants from the National Institutes of Health (Bethesda, Maryland) and the Doris Duke Charitable Foundation (New York).

The CONFIRM trial provided early evidence that AF is caused by localized electrical rotors or focal beats. These rotors, or as Narayan describes them, "localized areas of electrical activity" can be found all over the atria. They can be visualized using a physiological mapping system that utilizes a commercially available multi-pole basket mapping catheter.

Following the identification of the areas of electrical activity by the basket catheter, a proprietary algorithm displays the optical images and movies of the activation. Distinct geographic areas of waves of electrical activity generated in either the right or left atrium can be seen in almost all cases.

It is important to note that this technique is based on electro-physiological, not electro-anatomical, mapping. The latter approach dominates the AF diagnostic landscape today, led by the CARTO system from the Biosense Webster (Diamond Bar, California) division of Johnson & Johnson (New Brunswick, New Jersey) and the Ensite NavX system from St. Jude Medical (St. Paul, Minnesota).

A significant advantage of this approach, in addition to a higher level of efficacy, is that it may reduce or eliminate the need for anatomical mapping, which is widely used today. This would offer major cost and time savings.

The trial also provided early but promising signs that localized ablation of these rotors, which is called focal impulse and rotor modulation or FIRM, can acutely terminate or slow AF and improve efficacy when added to conventional AF ablation techniques. To wit, Dr. Narayan reported last year that the 32 FIRM guided patients achieved an 84% success rate, compared to only 51% for the 63 conventionally-treated patients.

Although it is still very early, some clinicians are already speculating that the success of FIRM ablation may ultimately represent a challenge to the widely-accepted belief that pulmonary vein isolation (PVI), today's "gold standard," must be performed to eliminate AF.

Even more impressive, about two-thirds of the treated patients had persistent or longstanding atrial fibrillation, which often requires a second or third catheter ablation to achieve success. The FIRM results were accomplished with a single procedure.

It is also very important to note that 84% of patients were followed up with subcutaneously implanted loop recorders, whereas less than a quarter in the control group had these devices. These "USB stick" sized devices record every heartbeat for the duration of their battery life and are considered to be by far the most accurate way to detect irregular heartbeats, such as AF.

At this year's HRS, Narayan reported more encouraging data, albeit still with relatively few patients. Specifically, a multi-center trial performed at nine centers with 33 patients showed that a 67% termination of AF, with another 17% showing a greater than 10% slowing in their AF.

Importantly, these cases were the very first cases performed by highly-regarded and experienced EPs who were not connected in any way to Topera or Narayan. The latter was not involved in any of these cases.

The study was performed with a standard basket catheter with the largest commercially available size of 6 cm, which limits basket contact and system performance in atria larger than this. Topera is developing its own basket catheter in a range of sizes that will address larger atria, which in turn should afford improved electrical performance.

Indeed, in the 26 cases where the left atrium was smaller than 6 cm and the basket fit the atrium, the results were even better: the AF was terminated in 81% of these cases, while an in additional 9% of the patients the AF slowed down by more than 10%. Once again, the lion's share of the patients suffered from persistent or long term persistent AF.

After Narayan's highly-anticipated presentation at HRS's annual Atrial Fibrillation Summit on Wednesday, Warren (Sonny) Jackman, MD, gushed "amazing . . . this is about to turn the AF ablation world upside down." Jackman, the director of clinical electrophysiology at the University of Oklahoma Health Sciences Center (Oklahoma City, Oklahoma), is widely regarded as one of the world's "gurus" of AF catheter ablation.

A poster session during HRS was extremely well attended, as clinicians were eager to gain more information about this exciting new approach to diagnosing and treating AF. The buzz at the show was certainly one of the major highlights of this year's HRS.

Skeptics certainly remain, pointing to the relatively small number of patients treated to date and the absence of a multi-center and randomized trial. However, there is no debating that this early data is highly promising.

Table 1 provides Medical Device Daily's summary of the system.

Topera, which licensed this technology about four years ago, received 510(k) clearance for the algorithmic-based mapping system, trade named RhythmView in September 2011. The company plans to submit a 510(k) for its own, larger basket catheter within the next couple of months. A domestic commercial launch is expected to occur in the first half of 2013. Topera hopes to launch the full system in Europe in the first quarter of 2013.

Table 1

Summary of Attributes and Benefits

  1. Rotors and focal beats were identified as driving AF in every patient, with multiple rotors found in about two-thirds of the patients

  2. The RhythmView system can also determine the mechanism of other arrhythmias (e.g., atypical atrial flutter, atrial tachycardia, atrial flutter)

  3. FIRM-only ablation (i.e., no PVI performed) procedures typically run about 90 minutes, "skin-to-skin." This significantly shorter time would be a boon to high volume private practices

  4. Significantly fewer RF ablation lesions are required to obtain "best in class" results, typically less than ten vs 100 to 200 for a PVI case

  5. Right atrial (RA) drivers are frequent. An RA-only procedure, estimated at 20% of the cases is feasible and could be performed without crossing the atrial septum

  6. Most cases to date have been performed with the proprietary mapping and standard fluoroscopy, thereby eliminating the need for time consuming electroanatomic mapping

2012 Heart Rhythm Society

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