The supplemental patient cohort about to join Endurance, the pivotal US trial testing HeartWare International’s heart pump as a permanently implanted artificial heart, ought to give insight into whether controlling patients’ blood pressure can decrease stroke. Interim Endurance data showed a slight increase in stroke rate with HeartWare's HVAD pump compared with a similar device, and it has been theorised that elevated blood pressure is the cause.
The trouble is that the company seems to be at odds with Endurance’s chief investigator over how the data will be used. Joseph Rogers of Duke University has said that data from the new cohort ought to be compared with those from the main body of the trial in order to properly test the blood pressure hypothesis. HeartWare, however, intends to integrate the data, lowering stroke rates overall and improving the device’s chances of approval.
20% extra free
The new cohort was initially planned to enrol 360 patients randomised 2:1 to HVAD or a control ventricular assist device (VAD). This has now been increased by nearly 20%, with an additional 286 HVAD patients and 143 controls, enabling HeartWare to increase the trial’s power. Full enrollment is expected to take a year.
Not only will the patients in the supplemental group have their blood pressure managed more strictly, the endpoint measure is different too, making HeartWare’s intention to mingle the data look very odd. The main Endurance group are being assessed on stroke-free survival at two years, whereas the supplemental group’s endpoint is stroke incidence at one year.
There is a further dispute about when data will be revealed. Dr Rogers has said that results from the original cohort of patients would be presented at the end of next year, obviously impossible if the data from the new set are to be included.
House brokers Canaccord Genuity wrote that tighter blood pressure control will improve the pump’s chances of approval as a permanent implant, giving it “a very good chance in absolute terms”. They point out that in an earlier trial of HVAD as a temporary measure before patients receive a heart transplant, centres that kept patients’ blood pressure low saw much lower stroke rates than those which did not manage blood pressure proactively.
A decreased rate of neurological complications detailed in the data submitted to the FDA may help the device get approved. But HVAD is already approved in the US as bridge-to-transplant therapy, and surely what will help HeartWare’s sales is proof that improved blood pressure control, relatively easy to achieve, abrogates HVAD’s stroke risk.
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