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NEW ORLEANS – The Impella 5.0 and 5.5 left ventricular assist device failed to measure up on outcomes when used for high-risk patients undergoing ventricular tachycardia (VT) ablation therapies, according to initial observational results in that indication.

At 18 months follow-up, freedom from the composite primary endpoint of risk of death, need for permanent left ventricular assist, or requiring cardiac transplant was achieved by 18 of 41 patients who used the Impella devices and by 18 non-Impella patients who were propensity matched to the patients (P=0.734).

Nor were there any secondary endpoint findings that favored the next-generation device, reported Jakub Sroubek, MD, PhD, of the Cleveland Clinic Lerner School of Medicine, at the Heart Rhythm Society meeting.

"Overall, this is a negative study," he said at a press conference here. "There are some limitations, needless to say, as it is based on propensity matching; the selection of patients was arbitrary, being dependent on the operator; and there were different criteria that each operator may have used."

Freedom from ventricular tachycardia at 18 months was achieved by eight patients treated with the Impella devices and by nine patients who were not treated with the device (P=0.768), he reported.

"Catheter ablation of ventricular tachycardia in high-risk patients is associated with high mortality and frequent recurrence," Sroubek noted.

The Impella 5.0 and 5.5 devices are high-flow axial-flow left ventricular assist devices approved for use in cardiogenic shock. They also have emergency use authorization for providing temporary left ventricular unloading and support in specific COVID-19 scenarios in the ICU.

The devices provide almost complete left-sided hemodynamic support, Sroubek said. They are inserted by the surgeon through the axillary artery usually the day before ventricular tachycardia ablation.

To look at potential benefits in high-risk ventricular tachycardia ablation procedures, Sroubek's group compared utility and safety of Impella 5.0/5.5 support versus historical controls in a single-center institutional database.

"This was a single center, retrospective study of 41 patients that we identified as being supported with Impella 5.0 or Impella 5.5, and as a control arm we used propensity matching ventricular ablations in a similar population," Sroubek explained.

Although failing to meet its objectives, he said the researchers observed some positives about it use. "We found that the Impella device did affect the immediate procedural outcomes," he said. "That means it allowed for induction of more ventricular tachycardia; it allowed us to map more ventricular tachycardia circuits, and perhaps and most importantly, it allowed more ventricular tachycardias to be terminated during the procedure, which to the community is sort of the Holy Grail of being 'successful.'

"And," he added, "it allowed for less unstable ventricular tachycardia induction, meaning there were less ventricular tachycardias that required external shock for ventricular tachycardia pacing. In that sense, it provided positive impacts on the procedure."

But the devices didn't impact the primary or secondary outcomes, and it let to significantly more complications: 12 complications in the Impella patients compared with just one complication in the non-Impella group.

However, "it should be said that even those that were major complications requiring re-operations, most of these were hematomas at the site of the implant, which is frequent in this surgical population," Sroubek noted. "As far as we know, these complications do not have an effect on clinical outcomes."

"This doesn't mean that Impella should be avoided in all patients; there are certainly some niche populations of patients that will benefit," he suggested.

In commenting on the study, press conference moderator Fred Kusumoto, MD, of the Mayo Clinic in Jacksonville, Florida, and immediate past president of the Heart Rhythm Society, questioned how well propensity matching works to eliminate confounding in this sort of situation.

"Patients who undergo ventricular tachycardia ablation are by definition very, very ill," Kusumoto told MedPage Today. "These are incredibly sick patients. When I think about using hemodynamic support for patients who have ventricular arrhythmias, it is going to be in those who are the most ill and the most sick, and therefore, as I implied, it is really hard to find a true control group for those patients.

"Because they are so ill, one has to worry about competing risk of death which might have nothing to do with the device, but may very well be progressive heart failure and things like that."

Rather than discouraging physicians from any use in VT ablation, Kusumoto suggested that the findings point to the need to be "very thoughtful in terms of using this sort of option."

"When this device first came out about 15 years ago, it was used more broadly and it was shown in multiple studies to not be a valuable strategy, but that doesn't mean it should not be used in specific populations," he said. "I think the Impella device could be useful in specific patients for whom hemodynamic support was needed while ventricular tachycardia mapping and ablation could be performed."

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