Medical Device Daily Washington Editor
The next time your cardiologist tells you that there’s something screwy going on, it might be good news. That is, if he or she is talking about the ventricular assist device (VAD) you just had implanted in your chest.
The “VAD news” is that the current generation of ventricular-assist devices, many of which make use of an Archimedean screw, are a vast improvement over their pressure-pump predecessors, and this technological advance has won over many of the doctors in attendance at the second day of the Heart Failure Society of America (St. Paul, Minnesota) annual meeting.
Leslie Miller, MD, the chief of the Integrated Divisions of Cardiology at Georgetown University Hospital (Washington) and the Washington Hospital Center (Washington) gave participants an overview of the progress that these devices present in dealing with partial or total heart failure.
Miller said that there have been “three major milestones” in the development of devices that assist the heart in pumping blood. The first milestone, he said, was in the transition from external pumps to internal pumps, and the second was the move from devices that depend on pneumatic power to push blood from the ventricle to the atrium to the use of electrical power sources.
The final milestone is still in play and consists of a transition of the mechanics of the pump itself. This is the transition from devices that push blood in a pulsatile fashion to devices that drive blood in a continuous flow.
In comparing in broad terms pump assist devices, Miller said that “the characteristic differences between the two are the size, the noise, but most importantly the durability.” Miller said that because continuous-flow devices entail less mechanical activity that involves impact between mechanical surfaces, they are less subject to wear and tear and hence can be expected to outlast the typical pulsatile device.
Miller said that the REMATCH trial, the now-famous three-year, $25 million assessment of the value of cardiac assists devices, was not only “a landmark in the field,” but also “a benchmark” in progress. He said that the REMATCH trial demonstrated a “26% absolute reduction in risk” of death at one year (52.1% of patients on VADs vs. 24.7% of patients on medical therapy) and that sepsis and neurological events were also down significantly.
Where quality of life (QOL) is concerned, REMATCH showed that patients on assist devices scored substantially better on depression and other such scores “despite going through a major operation and [having] issues with recovering” from a very invasive procedure.
Miller also recommended, however, that “patient selection is going forward the most important” element in determining outcomes.
“Those who are malnourished are at great risk for complications,” Miller said, especially for sepsis.
“These devices provide an incredible platform to study new drug therapy,” Miller said, pointing to clenbuterol as an example of a drug that has shown promise in helping a damaged heart heal. Clenbuterol is a bronchodilator that is currently not approved by FDA for any use, but a recent study in the UK indicated that when clenbuterol is administered in patients with ventricular assist devices, their hearts often recovered sufficiently to allow them to leave their VADs at the hospital.
“If we were able to do that with a larger number of patients,” Miller said, it would represent “a vital advance.”
Robert Kormos, MD, the medical director of the McGowan Institute for Regenerative Medicine (Pittsburgh) and the director of the artificial heart program at the University of Pittsburgh (Pittsburgh), said that new assist devices are in the pipeline and that even the DeBakey VAD may be staging a comeback.
According to Kormos, the DeBakey left ventricular assist device (LVAD) “enjoyed significant popularity in Europe some years ago,” but the company that now sports the DeBakey name, MicroMed (Houston), has come out with new models, including one for kids as young as the age of five.
Kormos said that to date, the DeBakey VAD, which is designed around the Archimedean screw, has been implanted in 434 patients across the world, including 151 in the U.S. The longest term of use in a patient is at 808 days. This device has a CE mark as well as a humanitarian device exemption from FDA, and it is the subject of an ongoing bridge-to-transplant trial for adults.
MicroMed did some work on the cannula to improve the inflow of blood, which Kormos said “got rid of some turbulence that may have led to some thrombosis.” He also said that the company has worked on spacing on the device’s rear hub that also might have contributed to thrombosis.
“I think it’s back,” Kormos said.
Australian firm HeartWare (Sydney, Australia) offers an LVAD that operates on a centrifugal pump that is tiny enough that it “fits within the pericardial sac,” Kormos said. Surgeons have implanted 20 of the HeartWare LVADs, but the device is new. The longest running implant is just over one year, and HeartWare is currently recruiting centers for a bridge-to-transplant trial in pursuit of a CE mark.
Another Australian firm, Ventracor (Chatswood, Australia) offers the VentrAssist, a VAD that operates on a hemodynamically-suspended titanium impeller that is moving into a pivotal trial. “One of the unique things is the flat HQ curve,” Kormos said, adding that the device provides a pressure that is “more like our natural heart than a flow device.” The VentrAssist has a CE mark, and the current data show an 85% survival rate to two years. Twenty-eight patients are enrolled in a U.S. pivotal trial.
Among the other VADs Kormos discussed was the Impella 2.5 made by Abiomed (Danvers, Massachusetts). The Impella installs percutaneously and straddles the aortic valve to drive blood from the left ventricle to the left atrium. “The nice thing about this device is that it installs much like an aortic balloon pump,” but it has demonstrated no adverse effect on aortic valve.