HeartWare VAD bridge experience shows at least 90% six-month...

HeartWare VAD bridge experience shows at least 90% six-month survival
MARCH 16, 2011 | Steve Stiles

Washington, DC - Nine patients out of every 10 who received a HeartWare (HeartWare International) continuous-flow ventricular assist device (VAD) as a bridge to possible transplantation were alive at six months, usually on continued device support or with a new heart, according to a prospective 50-patient international experience reported in the March 22, 2011 issue of the Journal of the American College of Cardiology [1]. Almost 80% were alive at two years.

"During [HeartWare] VAD system support, hemodynamic status, quality of life, and neurocognitive function improved for the majority of patients," according to the authors, led by Dr Martin Strueber (Hannover Medical School, Germany).

In the study, one of the first of patients fitted with the HeartWare device, "the two-year survival rate was similar to that of heart transplant, which suggests that this long-term therapy is promising for the heart failure population," they write.

The HeartWare is a continuous-flow device like the more extensively studied Heartmate 2 (Thoratec) but differs in being magnet-driven and connected to the heart within the pericardial space. That avoids the need for abdominal surgery to create a pocket to contain the device, as required by the Heartmate 2, Strueber et al observe.


HeartWare VAD in pericardial space [Source: HeartWare]
Two years ago, the same team reported a 91% six-month survival for the first 23 patients of the current cohort, as covered then by heartwire. Later they reported an 86% one-year survival for those same patients [2].

Also recently presented, but yet to be published, is the ADVANCE HeartWare bridge-therapy experience in 140 patients, who were compared with similar patients in the INTERMACS registry (most of whom had received a Heartmate 2 device, according to the investigators).

The rates of survival, explantation, or transplantation at six months reached 92% for the ADVANCE patients and 90% for the INTERMACS controls, meeting the criteria for noninferiority at p<0.001, as reported by heartwire.

The author of an editorial accompanying the report from Strueber et al [3], Dr Salpy V Pamboukian (University of Alabama, Birmingham), told heartwire that it's possible that some specific patient groups, like those with smaller body size, might benefit from the HeartWare VAD's placement in the pericardial space. But so far, "I don't perceive that there's going to be major clinical differences between the pumps in [their ability to] support a failing heart," she said. "I think they're both going to be fine devices."

The 50 transplant-eligible patients in the current series received the HeartWare VAD at five centers in Europe and Australia from 2006 to 2008. Their mean duration of pump support was 348 days, and there were "no mechanical failures."

Transplantation occurred in 40% after a mean of 267 days of VAD support, and the devices were explanted after recovery of ventricular function in 8% of cases.

Of the group, 47 were discharged from the hospital after a mean of 45 days. Their rate of readmission for complications was 1.24 per patient-year, "which is a 74% reduction when compared with the average admission rate of this group for the year before their [HeartWare] VAD implants," the group writes.


Other findings

Actual survival was 90% at six months, 84% at 12 months, and 79% at 24 months.
Mortality during HeartWare VAD support was 18%; with deaths caused by sepsis, multiple organ failure, and hemorrhagic stroke, three cases of each.
Health-related quality of life (as measured by the Kansas City Cardiomyopathy Questionnaire in 28 patients) improved significantly with respect to symptoms, physical limitation, and overall functional status; the gains were mostly in the first 30 days of HeartWare VAD support. "Recognition memory" improved significantly within three months of implantation.
Infections were the most common complication, occurring at a rate of 0.20 events/patient-year; they were most likely in the first month.
Bleeding events necessitating surgery, transfusion, or repeat hospitalization occurred at the rate of 0.33/patient-year in the first month and 0.11/patient-year thereafter.
Seven patients required device change-outs, in two cases because of "manufacturing variability of the thrust bearings" and in four cases because thrombus ("suspected to be from the left ventricle") had entered the pump.
In her editorial, Pamboukian describes several challenges the devices face in gaining widespread use. The need for small and durable devices that provide long-term support and longer survival "has been overcome to a significant degree," she writes. Infections, especially related to percutaneous insertion sites of the pumps' driveline and power lines, and the risks of bleeding and thrombotic complications are likely to be less important with technological advances.

A more difficult challenge to conquer, she writes, is acceptance of the therapy by "the greater cardiology community."

To heartwire, Pamboukian said that no published report of data can match witnessing patients' clinical improvement on VADs for convincing physicians that the devices work well. "When they see the patients on the device and see the technology in action and how well the patients do, that's really a selling point."

It's not unusual, she said, for her practice to arrange a visit between their VAD recipients and referring physicians, "so the referring physician can see the outcome of the referral. That's been a very powerful mechanism for increasing referrals in the community."


HeartWare complications in the news

As reported in the media last month, a Milwaukee, WI hospital recently suspended HeartWare implantations allegedly after one of them malfunctioned due to thrombus. The patient developed an intracranial hemorrhage sometime after receiving a thrombolytic agent intended to clear the clot away.

Experts who spoke with heartwire at the time were "surprised to learn that a hospital chose to suspend implants" after the episode, noting that thrombus formation is a recognized potential complication of VAD therapy that is about as common with the HeartWare VAD as with the Heartmate 2.

Pamboukian observed that risks of bleeding and thrombus "are part of the business" of VAD therapy. Referring to the recent incident, she agreed it would be unfair to single out the HeartWare VAD as being riskier, "because all the devices we use have potential for clot in the pump."

In the current series, thrombus development in several pumps necessitated device replacement. Afterward, according to Strueber et al, "it was determined that manufacturing variability of the thrust bearings resulted in an area of reduced flow that could have been more prone to thrombus formation." The problem was resolved with manufacturing changes, they said.