Preventive or Deferred VT Ablation With Postinfarction ICD?

February 10, 2020

One of the latest questions about postinfarction ablation of ventricular tachycardia (VT) addressed in a randomized trial isn't a new one: Should it be done preventively at the time of defibrillator implantation, or deferred until after the device delivers appropriate shocks, if that time ever comes?

The BERLIN VT trial was terminated early after an interim analysis showed no sign the preventive strategy would surpass deferred ablation for mortality or rehospitalization for ventricular arrhythmia or heart failure (HF), the primary end point. But several secondary end points went in favor of preventive ablation.

Patients who had VT mapping and ablation on receiving their implantable cardioverter defibrillator (ICD) later showed fewer sustained ventricular arrhythmias and experienced fewer ICD treatments than those in the deferred group.

Those findings were from an unadjusted, exploratory analysis, and at any rate were offset by a numerically greater number of nonarrhythmic deaths, notes the BERLIN-VT report, published January 31 in Circulation.

Therefore, "the trial findings support current clinical practice, which assumes that there is no advantage to a preventive ablation strategy in regard of patient outcomes," write the authors, led by study chair Stephan Willems, MD, University Heart Center, Hamburg, Germany.

"Thus, catheter ablation in patients with ischemia-related VT and a secondary prevention ICD indication should be postponed until VT recurrence after ICD implantation, thereby avoiding exposure of patients to the risk of unnecessary preventive ablation."

Neither Willems nor senior author Karl-Heinz Kuck, MD, LansCardio, Hamburg, responded to interview requests from | Medscape Cardiology.

BERLIN-VT builds on several decade-old trials, including SMASH-VT and VTACH, that collectively suggested preventive VT ablation in postinfarction patients can reduce the subsequent burden of ventricular arrhythmias and lower the risk for ICD shocks and antitachycardia pacing (ATP).

Those would seem worthy goals, given associations between shocks and increased mortality risk, and their potential for permitting less antiarrhythmic drug therapy and improving quality of life.

At the time BERLIN-VT was halted at a mean follow-up of 396 days, the report notes, 32.9% of the 76 ICD recipients randomized to preventive VT ablation and 27.7% of the 83 in whom ablation had been deferred had reached the primary end point.

"Neither the primary outcome nor any component of it differed significantly between the two groups," the authors note.

"It's fair to say that maybe preventive [VT ablation] is not quite ready for prime time without more data. But there's no doubt it prevents VT. We can say without a doubt that it's effective at doing its job," Francis E. Marchlinski, MD, told | Medscape Cardiology.

But with its primary end point of mortality and HF hospitalization, the BERLIN-VT trial "set the bar too high," said Marchlinski, Hospital of the University of Pennsylvania, Philadelphia, who is not associated with the trial.

All patients in both groups had ICDs, so all had a low risk of dying from the kind of arrhythmias VT ablation is intended to prevent. "Then you take a population of patients who are pretty well to begin with, and you end up with a good chance of having more deaths from other causes," he said.

Mean age in the trial was 66 years; it did not enroll patients with a left ventricular ejection fraction below 30%, and the mean was 41%.

"The data, I think you can argue, suggest that although there was a benefit [from preventive ablation] in terms of VT reduction, the study was stopped early and so can't really say whether there would have been a long-term benefit in reducing ICD shocks," Marchlinski said.

An adequately powered study that is like BERLIN-VT but with reversed end point priorities — arrhythmia and shock reduction becoming primary, and mortality and hospitalization moving to secondary status — would more reliably show the effect of preventive VT ablation on ventricular arrhythmia burden, he proposed.

"We need more data on this, to say whether we are effective in preventing VT and recurrent episodes, and ultimately preventing shocks from the device," said Marchlinski.

Interestingly, many clinicians in the study did not abide by a protocol recommendation that ablation be avoided in the deferred-ablation group at least until the patient had experienced three ICD shocks.

"Catheter ablation in the deferred ablation group was predominantly performed after the first or second ICD shock," the report notes; suggesting that in practice, the three-shock minimum before ablation is "generally not adhered to by most physicians, and might also not be accepted by patients."

"The physician operators spoke with their actions, didn't they?" Marchlinski said. "It shows that they couldn't bear patients having more than one or two shocks."

Earlier VT ablation, not a delay until after three shocks, should be the standard. "Right now, the problem is not that we're doing it too early, but we are doing it still too late," he said.

"Certainly when the patient gets a first recurrent episode of ventricular tachycardia, and certainly when they get their first shock, it's reasonable for us to have a nice discussion with them about using ablative therapy as a treatment option."

BERLIN-VT prospectively enrolled patients with prior myocardial infarction and an LVEF of 30% to 50% who were slated to receive an ICD; all were set up for automatic daily home monitoring. They came from 26 centers in Germany, Hungary, Russia, the Czech Republic, and Switzerland.

Patients were randomized to a preventive (prior to device implantation) or deferred (after a third appropriate shock) VT ablation strategy. Ultimately, 12% of the deferred group underwent VT ablation at a median 46 days after randomization.

The hazard ratio (HR) for the primary end point in the preventive vs deferred group was 1.09 (95% CI, 0.62 - 1.92; P = .77). Six patients died in the preventive group, although four deaths were noncardiac and one was considered secondary to a transcatheter valve procedure complication. Two patients in the deferred group died (P = .18).

Fifteen preventive and 21 deferred patients were hospitalized for symptomatic ventricular arrhythmia (19.5% vs 25.3%; P = .27).

The preventive ablation group, compared with the deferred group, showed numerically fewer episodes of sustained ventricular tachyarrhythmia (39.7% vs 48.2%), whether hospitalized or not, and appropriate ICD therapies (34.2% vs 47.0%).

Secondary Arrhythmic End Points in BERLIN-VT, Preventive vs Deferred VT Ablation
End Point HR (95% CI) Log-rank P
Sustained VT/VF 0.62 (0.38–1.00) .047
Appropriate ICD therapy 0.55 (0.33–0.91) .018
Appropriate ATP 0.57 (0.34–0.95) .027
VT = ventricular tachycardia; VF = ventricular fibrillation; ATP = antitachycardia pacing

Eight preventive and two deferred patients (10.4% vs 2.3%; P = .062 by Cox regression) were hospitalized with worsening HF. The difference reached significance in a log-rank analysis (HR, 4.37; 95% CI, 0.93 - 20.6; = .041).

That the risk for hospitalization for worsening heart failure was at least numerically higher in the preventive ablation group "might be attributed to volume overload during ablation with irrigated catheters," the BERLIN-VT report notes.

That recognized risk for the ablation procedure is usually manageable, Marchlinski pointed out. "We know that patients, if they get a lot of fluid for an ablation procedure, are going to have a higher risk of heart-failure admission."

But in BERLIN-VT, "it wasn't prespecified how they were going to manage volume load, and prevent people from having early hospitalization for re-accumulating fluid that was put in during the procedure."

And that, he said, "sort of stacked the deck" against the preventive approach.

BERLIN-VT was sponsored by Biotronik. Willems reports receiving personal fees from Boston Scientific. Kuck discloses personal fees from Medtronic, Boston Scientific, Biosense Webster, Abbott, and Edwards Lifesciences. Disclosures for the other authors are in the report. Marchlinski reports serving on scientific advisory boards for Medtronic, Abbott/St Jude Medical, and Biosense Webster, and receiving lecture honorarium from Abbott/St Jude Medical, Biosense Webster, Biotronik, Boston Scientific, and Medtronic on topics related to VT mapping and ablation.

Circulation. Published online January 31, 2020. Abstract

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