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As destination therapy for advanced heart failure, the novel HeartWare left ventricular assist device (LVAD) performed on par with the FDA-approved HeartMate II LVAD device in a randomized trial -- but with some safety concerns.

The proportion of patients who survived 2 years after implantation without disabling stroke or device malfunction leading to LVAD removal was (55.4% versus 59.1% for HeartMate II, P=0.01 for non-inferiority), according to , of Duke University Medical Center in Durham, N.C., and co-investigators of the ENDURANCE trial.

LVAD malfunction or failure requiring replacement was numerically more common among HeartMate II recipients (16.2% versus 8.8%), the study published in the Feb. 2 issue of the New England Journal of Medicine showed. HeartWare, on the other hand, trended towards more deaths (34.7% versus 26.4%).

"An analysis of the components of the primary endpoint showed no differences between the study group and the control group with regard to death, disabling strokes, or imputed study failures," the authors nonetheless wrote.

The HeartWare device uses a smaller, centrifugal-flow design aimed at reducing thrombus formation by eliminating bearings and instead relying on magnetic and hydrodynamic rotor levitation. It is smaller than the continuous axial-flow HeartMate II LVAD, which provides continuous axial flow, and sits entirely in the pericardial space.

However, even with those design features, the HeartWare failed to show an advantage in the rate of pump exchange due to LVAD thrombosis, Rogers and colleagues reported.

HeartWare was associated with more strokes (29.7% versus 12.1%, P<0.001). Also, HeartWare recipients were more likely to develop right heart failure (38.5% versus 26.8%, P=0.02) and sepsis (23.6% versus 15.4%, P=0.048) during follow-up.

From 2010 to 2012, the ENDURANCE trialists randomized patients to the HeartWare (n=297) or HeartMate II LVADs (n=148). Participants had advanced heart failure and weren't candidates for heart transplants.

Use of antithrombotics was up to the discretion of operators throughout the study.

Rogers and colleagues acknowledged that the HeartWare that they started with at the beginning of the trial wasn't the one they ended up with: the LVAD evolved in the middle of the study (when the first third of patients were already enrolled) with changes to the inflow cannula and a modified coring tool for the ventricle.

In an accompanying editorial, clinicians expressed disappointment with the HeartWare and another new centrifugal-flow LVAD, St. Jude Medical's HeartMate 3.

Data from the MOMENTUM 3 study, first presented in November 2016 at the annual scientific sessions of the American Heart Association and now published in the same issue of NEJM, showed that HeartMate 3 was better at avoiding pump thrombosis than its predecessor, the HeartMate II.

"It is clear, however, that the newest devices have not yet resolved some of the most important problems with LVAD support. It is disappointing that there was no benefit with either of the magnetically levitated centrifugal pumps, as compared with the axial-flow pump, in reducing the risk of bleeding or sepsis," wrote , and , both of Germany's Cardio Centrum Berlin.

"The risk of right heart failure was not lower with the HeartMate 3 than with the HeartMate II and was actually higher with the HeartWare device," they continued. "Most importantly, stroke risk was not reduced; the overall stroke risk was higher with the HeartWare pump and was not significantly lower with the HeartMate 3."

Hetzer and Walter questioned whether trials can really show that adjustments in the antithrombotic regimen decrease the risk of stroke with these LVADs.

In the meantime, the duo concluded: "The data from MOMENTUM 3 and ENDURANCE revealed to us that none of the pumps is fully superior to the others. The perfect approach to mechanical circulatory support in advanced heart failure has not yet been achieved."