John Mandrola, MD


May 10, 2016

Three late-breaking clinical trials at the Heart Rhythm Society (HRS) 2016 Scientific Sessions taught us a lot about atrial-fibrillation ablation.

Can Contact-Force Ablation Catheters Pass a Real Test?

I don't ablate AF with contact-force (CF) catheters. I find them stiff and clunky; I also hate the excess saline load they deliver. But I am an outlier. Most operators value the CF information.

Until the HRS meeting was held, no head-to-head comparison study looked at whether CF improved outcomes. To answer this question, a team from the UK performed[1] AF ablation in one group of patients (n=59) in which the operator knew the CF vs a control group in which the operator used the same catheter but was blinded to the CF (n=58).

Knowledge of CF made no difference in the rate of AF recurrences at 1 year or procedural complications.

This negative outcomes study teaches two broader lessons. The first is the issue of trade-offs. Contact force seems like a nice number to know. But it doesn't come free. The cost is a less nimble catheter. How does that affect ablation lesions in the left atrium?

The second lesson is, how did an unproven catheter win such broad appeal? I can remember a key opinion leader telling a group of experienced operators that the "end of arrogance" was over. His points were that if you don't accept new technology, you are arrogant, and that you can't feel a catheter making good contact. I wondered if he actually does cases. This is where disclosure slides are key.

Numbers on a screen don't make arrhythmias go away; humans with well-honed neural pathways do.

Can Rotor-Guided Ablation Be Replicated?

Few experts deny the existence of rotors during AF. The debate now centers on whether proprietary mapping systems can reliably detect rotors and then guide ablation. Previous studies with the FIRMap, (Abbott, Chicago, IL—formerly Topera) have shown promise.[2,3] These studies, however, were not randomized. Recently, other groups have been unable to replicate earlier results.[4,5,6]

In the final late-breaking session at the HRS meeting, Dr Andrea Natale (Texas Heart Institute, Austin) presented the OASIS trial,[7] the first randomized controlled trial comparing the efficacy of focal impulse and rotor modulation (FIRM) ablation, either alone or as an add-on to pulmonary-vein (PV) isolation in patients with persistent or long-standing persistent AF (PAF).

The OASIS researchers did a three-arm trial. One group (n=29) got FIRM-guided ablation alone; a second group (n=42) had PV isolation plus FIRM ablation, and a third group (n=42) got standard PV isolation. (A note on technique: standard PV isolation for this group includes complete isolation of the posterior wall of the left atrium and ablation of any focal triggers induced with high-dose isoproterenol—a decidedly more aggressive approach than most labs.)

After 1 year of follow-up, only 14% of patients ablated with FIRM alone were free of AF. (They terminated that arm early due to futility.) Adding FIRM to PVI increased the success rate to 52%; but PVI without FIRM resulted in a 76% success rate. Procedure time and X-ray exposure were significantly higher in the FIRM groups. Adverse events were not significantly different.

For FIRM-ablation believers and recent purchasers of the expensive mapping system, this study is as bad as it gets. Patients in the FIRM arms were exposed to longer procedure times and more radiation without any benefit. On Twitter, Dr T Jared Bunch (Intermountain Heart Institute, Utah) wondered if FIRM ablation was proarrhythmic. Dr Gopi Dandamudi (Indiana University, IN) said of FIRM ablation: "Stark reminder [that] new tech/methods don't always translate to outcomes; [they] just add more cost."

FIRM ablation does have one shining star. Dr John Miller (Indiana University, IN) and colleagues (who include Dandamudi) continue to publish positive studies using FIRM. In a featured poster presentation, Miller reported[8] a series of 170 patients, nearly half of whom had failed previous ablation, in which single-procedure FIRM-guided ablation yielded good intermediate-term results off antiarrhythmic drugs. I'll admit it: when the pulmonary veins are isolated and the patient still has AF, I think about a machine that could tell me where to burn.

Is It the PVs, or Something Else?

Common thinking holds that successful AF ablation requires durable electrical isolation of the pulmonary veins. Two observations challenge that notion: FIRM pioneer Dr Sanjiv Narayan (Stanford University, CA) once told me that PV isolation may work because it (coincidentally) hits rotors. He's got a point; because the second challenge to the necessity of PV isolation is the observation (GAP,[9]EFFICAS I,[10] and EFFICAS II[11]) that many ablated patients have reconnected veins and no AF.

Dhiraj Gupta (Liverpool Heart and Chest Hospital, UK) explored this reconnection post–PV isolation in another late-breaker at the HRS meeting, the novel and controversial PRESSURE trial.[12] The senior investigator tested the hypothesis that a strategy of invasive assessment 2 months after AF ablation, regardless of symptoms, with reisolation of reconnected PVs, would improve arrhythmia-free survival.

You read that correctly. In this multicenter trial, 80 patients with PAF were randomized at the end of their index PVI procedure. In the active arm, 40 patients went back to the EP at 2 months and had reisolation of reconnected veins. The control arm included 40 patients who received standard care; reablation was done only for symptoms and documented AF.

The initial procedure averaged 165 minutes, while repeat procedures took only 80 minutes. No patient suffered a complication during a repeat procedure.

In the repeat-procedure arm, 62% of patients had reconnected veins. Reisolation took (on average) only 5 min of ablation and 8 min of fluoroscopy time.

The strategy of routine repeat procedures proved superior: At 12 months, 33/40 (82.5%) patients in the repeat-strategy group were arrhythmia-free vs 23/40 (57.5%) of the standard-care group. The repeat strategy led to higher quality-of-life scores; one patient in each arm suffered a complication.

Dr Gupta faced tough questions in the postpresentation Q&A session about exposing asymptomatic patients to unnecessary procedures. One critic noted that it was only a matter of time before an asymptomatic patient had a complication. Gupta responded that the higher benefits have to be weighed against the shorter, less burdensome, repeat procedure. He told me after the session that his next step was a cost analysis. The extra procedure adds cost, but it's possible the lower AF burden may save money in the long term.

I like the PRESSURE trial because it makes you think.

I'm not saying we should adopt repeat procedures in all patients, but I agree with Gupta's take of the redo procedure. In experienced operators' hands, the chance of complications from the second procedure is quite low. And if it delivers higher long-term relief of AF, it might be both cost-effective and patient centered. I would like the strategy a lot more more if it's applied only in a non–fee-for-service model.

The most important message from PRESSURE is what it says about the mechanisms of AF. Accepting the caveats of wide confidence intervals, PRESSURE seems to confirm the role of the PV musculature in paroxysmal AF. If ablation around the PVs worked only because it coincidentally hit rotors or disturbed neural modulation of the atria, you'd expect no difference after a few spot-welding ablation lesions in the second procedure.

Let me know what you think in the comments. These trials make for good conversation.



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