John Mandrola, MD

Disclosures

November 14, 2016

A lot has changed in AF ablation. Catheters, mapping systems, and approaches have evolved over the past 15 years. In cardiology, such changes usually lead to marked improvements in procedural success. Witness the transformation of the care of patients with acute MI and the ease of placing cardiac resynchronization devices.

Not so much in AF ablation.

In session titled "Outcome of Ablation of Atrial Fibrillation" at the American Heart Association 2016 Scientific Sessions, researchers from Stanford University, with senior author Dr Mintu Turakhia, presented the results of a systematic review and meta-analysis of the published literature on ablation for paroxysmal AF over the past 2 decades[1].

They looked at 194 studies including nearly 30,000 patients. They excluded studies without insufficient reporting of outcomes and ablation strategies that were not prespecified and uniform.

Procedural success rates in 2003 were 70.3%, increasing to 75.6% in 2016. After controlling for covariates, they observed a mere 0.5% increase in success rate per year from 2003 to 2016. They noted an abrupt drop in success rates in 2007, followed by a gradual rise from 2007 to 2016. This blip probably reflected guideline recommendations to increase postprocedure monitoring.

The authors concluded (italics mine) that success rates for paroxysmal AF have improved only incrementally, and with these current trends meaningful improvement in success rate is unlikely to occur without a major change in paradigm or technology.

Comments

I spoke with lead author Dr Alexander Perino here at the AHA meeting. He first emphasized the limits of their analysis: significant heterogeneity remains unaccounted for in meta-regressions. (I appreciate leading with the limits of a study.)

Heterogeneity in a meta-analysis is a problem because you can't find truth when comparing apples and oranges. Perino said the variability of studies included in this review should not affect the trends of ablation success over time.

And the trend is clear: we've hit a plateau in procedural success rates.

Despite thrilling advances in 3D mapping systems, irrigated catheters, contact-force sensing catheters, and yes, even intracardiac echo, we have hardly budged the success rate of AF ablation.

The reasons for this plateau deserve attention.

Perino suggested one reason for the plateau is stricter grading. Namely, recent studies used tighter definitions of success and had longer follow-up. Gains in technology may have been offset by better studies.

I doubt it. I think these results expose the essence of the problem with AF ablation—a massive knowledge deficit. When you don't know the cause of a disease, it's little surprise that success rates budge so little.

We know so little about AF that it's hard to even define "success" of ablation. Does success mean elimination of AF episodes? Maybe. But maybe AF episodes are mere surrogates that don't influence stroke rates. Or maybe we eliminate AF episodes but don't change the atrial substrate and therefore stroke risk remains high.

Should success simply mean improving our patients' quality of life? Clearly, many patients feel better after ablation. That's great. But it's a risky and expensive way to palliate symptoms. What's more, if you argue palliation is enough, we need a properly controlled sham-controlled trial.

Another problem: AF is darn heterogeneous. You can see an obese patient who has a completely normal left atrium and obvious focal triggers. This patient responds nicely to pulmonary-vein isolation. The next day you may see a thin patient with diffuse low voltage in the LA, and there's little chance pulmonary-vein isolation will eliminate AF—or maybe it will. Seriously, this is where we are at . . . almost 2 decades into the AF-ablation experience.

Paradigm change means embracing a new worldview. I feel some slow progress. But the forces of understanding this disease and narrowing the number of patients who benefit from ablation are strong. Redo procedures, for instance, are quite profitable. The US market size for AF ablation is in the billions of dollars.

But there's more at stake here than just reducing the wasteful spending on ablation. Think about the public-health implications for understanding the role of risk factors in reversing atrial substrate—and likely stroke risk.

In another AHA session here, Prof Isabelle van Gelder (University of Groningen, the Netherlands) referred to an "AF epidemic." Her talk detailed many ways to halt that epidemic. These included modifying endothelial dysfunction, atrial stretch, inflammation, and vagal and adrenergic influences. Nowhere on her slide was putting 80 burns in the left atrium.

If the middle-aged patient with AF loses weight, gets fit, and limits alcohol intake, then his blood pressure and glycemic control improve. If that happens, not only does AF risk decline, but more important, the risk of stroke, heart attack, and dementia also decline.

A worldview that sees an ECG recording of AF as more than just a target for catheter ablation can't come soon enough. Good on the Stanford researchers for helping us see the obvious.

JMM

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