Former Vice President Dick Cheney's new left ventricular assist device (LVAD) may pump up interest in destination therapy among severe heart failure patients, researchers say.
Although a second-generation device, the HeartMate II, was FDA approved for long-term use in January for advanced-stage heart failure in those not eligible for heart transplant, uptake of the technology for this indication has been slow.
But the publicity could turn the tide.
"Since [the approval], we have not seen a tremendous increase in patients, as was expected," David D'Alessandro, MD, of Montefiore Medical Center, in New York City, said in an e-mail to 51成人动漫 and ABC News. "But I suspect that Mr. Cheney's misfortune ... will likely result in increased national awareness, which will ultimately bring this little known frontier of medicine to the forefront."
He attributed the slow adoption to "lack of awareness among both patients and physicians."
LVADs have been in development since the 1950s, with the first wave of routine use in the 1990s as a bridge to heart transplant, according to Lishan Aklog, MD, of St. Joseph's Hospital and Medical Center in Phoenix. The first generation of devices were large and bulky, and used pulsatile pumping technology.
They were also "plagued by a relatively high incidence of thromboembolic complications, primarily strokes, drive line infections, and mechanical failures," Aklog said.
Nonetheless, in 2003, the HeartMate XVE was approved for use as destination therapy, after the REMATCH trial found it to improve one- and two-year survival compared with standard medical therapy (52% and 23% at each time point, respectively, for the device versus 25% and 8% for standard care).
But advances in technology led to the introduction of the second-generation devices, notably HeartMate II, which was approved as a bridge to transplant in 2008.
Its improved design made it more reliable, researchers say. As a continuous flow device, it didn't have the same mechanical problems as the pulsatile pumps, in which an inflow valve would usually fail within a year.
"That pump wasn't designed to go long term," Gregory A. Crooke, MD, a cardiothoracic surgeon at Maimonides Medical Center in Brooklyn, told 51成人动漫. "It was designed to get people to transplant. Loads on the inflow valve put a lot of stress on it, and it failed very quickly."
In addition to its improved, continuous flow design (which some say makes patients appear to lack a pulse), the HeartMate II was also significantly smaller. In 2009, the HeartMate II Destination Therapy (HMII) trial found that significantly more patients survived stroke-free and replacement-free at two years with the second-generation device compared with the first.
One- and two-year survival rates were 68% and 58% with HeartMate II versus 55% and 24% with HeartMate XVE.
So, in January 2010, the FDA approved the HeartMate II as destination therapy in severe heart failure patients, with the caveat that patients also be put on anticoagulation therapy to ward off the strokes associated with the earlier devices.
It's the only second-generation device to have such approval.
Destination therapy trials of third-generation devices are set to begin in the U.S. in "a couple of months," according to Frank Pagani, MD, of the University of Michigan.
Those include the HeartWare, which is smaller than HeartMate II, and the DuraHeart, which is about the same size, he said.
The National Institutes of Health (NIH) are supporting a number of initiatives, including the INTERMACS registry, to which all centers participating in destination therapy must report outcomes.
NIH also is behind the REVIVE-IT trial, which is assessing long-term LVAD use against medical therapy for patients with less advanced symptoms than currently indicated.
Researchers hope the trial will provide some clarity as to which heart failure patients should be indicated for the device. Currently, clinicians are using the criteria from the HMII trial, which include a left ventricular ejection fraction of less than 25%, a myocardial oxygen consumption of less than 14 ml/kg of body weight per minute, and NYHA Class IIIB or IV heart failure.
"That is the ongoing debate," Crooke said. "How early should we put this in? If we put it in too late, will we incur morbidity and mortality? Or are we putting them into people who don't really need them?"
He said the trend has been to look at patients at the end of Class IIIB heart failure who aren't immediately dying but would be predicted to have bad one- or two-year outcomes.
In order make those predictions, Crooke said researchers are looking at "things that we would never have thought of as a hallmark of death in the next 12 months," including slight elevations in international normalized ratio (INR) and slight drops in platelet counts -- rather than the big markers like multiple hospital admissions.
He added that the devices certainly won't be used in patients with earlier stages of heart failure.
"Just to look at class III represents a big shift in thinking," he said.
According to a spokesperson for device maker Thoratec, there are more than 4,000 HeartMate II patients worldwide, although the company does not have numbers on how many HeartMate devices are specifically used for destination therapy.
More than 120 centers in the U.S. are certified to implant the HeartMate II device, with 78 of them certified for destination therapy. To be certified, hospitals must meet several criteria, including having a surgeon with experience in implantable devices as well as a specialized team dedicated to doing the procedures.
Researchers estimate that the device costs between $80,000 and $100,000.
This article was developed in collaboration with ABC News. 