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HeartMate II offers small size, applicability to more patients
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A new bridge-to-transplant technology is now available for patients in need of a left ventricular assist device.
Thoratec Corporation’s HeartMate II LV assist system, a continuous-flow LV assist pump based on the design of an earlier and larger HeartMate XVE pulsatile device, received a unanimous recommendation for approval by the Circulatory System Devices Advisory Panel in November 2007. The FDA recently approved the HeartMate II’s premarket application in April and approved use of the device as a bridge-to-transplant therapy.
Smaller design
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Source: Thoratec Inc. |
According to the manufacturer, the function of the HeartMate II is to restore hemodynamic function in patients with advanced-stage HF. At full capacity, the device is capable of pumping up to 10 L per minute, comparable to the output of a healthy heart.
The inflow conduit is attached surgically to the left ventricle, and the outflow conduit is attached to the aorta; they were designed to be flexible and to accommodate smaller body cavities and anatomical differences. The device’s central housing unit contains the rotor, which is the device’s only moving part. The internal apparatus is connected to a power cable that passes through the patient’s skin and is attached to a battery-powered energy source and flow regulator worn by the patient on an external belt.
A chief advantage of the HeartMate II, according to physicians familiar with the device, is its reduced size. The entire axial-flow pump housing that contains the rotor responsible for moving the blood through the device is about the size of a D battery and weighs about 400 g.
“There is no question that its size and simplicity are important,” James B. Young, MD, professor of medicine at the Cleveland Clinic Lerner College of Medicine and section editor of the Myocardial Disorders, HF and Transplantation section of the Cardiology Today Editorial Board, said in an interview. “It is an easier device to insert. You can put the device in the chest as opposed to putting it in the abdomen, and the transcutaneous lines are much smaller than the lines associated with the pulsatile devices.”
Regulators from the FDA also indicated the potential benefits of the device’s smaller size, which would allow for the previously hazardous implantation in women, smaller-bodied men and adolescents.
Results from a prospective, multicenter trial published in The New England Journal of Medicine suggested that the safety and efficacy profile of the HeartMate II as a bridge-to-transplant therapy was at minimum comparable to that of other approved heart devices. Data from one-year follow-up of the completed trial were also critical in the FDA’s decision to approve the HeartMate II.
Researchers from several sites in the United States enrolled 133 patients with end-stage HF who were also on waiting lists to receive heart transplantation. The principle outcomes – reaching transplantation, survival or cardiac recovery at 180 days after implantation — occurred in 100 patients (75%). Fifty-six (42%) received heart transplantation, 43 (32%) had ongoing support from the HeartMate II after 180 days awaiting transplantation and one patient recovered cardiac function. The most common adverse event in the trial was bleeding, particularly in the time following implantation. Twenty-five (19%) of the patients died either before transplantation or prior to 180 days.
In addition to the one-year follow-up and postmarketing studies that will follow the FDA’s approval, there is also a trial currently being conducted to assess the long-term safety and efficacy of the HeartMate II.
“There is an ongoing second component of the pivotal trial, which is looking at this device for destination therapy or permanent device use, and that randomized trial is being compared with the original HeartMate XVE,” said Francis Pagani, MD, PhD, associate professor of cardiac surgery at the University of Michigan School of Medicine.
Future directions
According to Pagani, the current emerging ventricular assist device technologies may be moving in the direction of new devices that are reduced in size while playing a supporting role for the native heart.
“There is a third generation of devices, and some of those devices might be bigger, some might be smaller,” Pagani said. “Where the technology is leading us is toward smaller devices that do not have the ability to pump all of the blood but rather a partial amount of blood, and they can be put into patients in earlier stages of their HF.”
Although the larger pulsatile devices like the HeartMate XVE can pump more blood than its smaller counterpart, LVAD technology has not yet allowed the devices to replicate or replace the function of the heart entirely.
“The HeartMate cannot be used very easily as ventricular replacement technology,” Young said. “It is best for these devices to have the native heart having some output and some contractility in reserve, so it truly is an assist device as opposed to a replacement device.”
Despite the device’s limited role, Pagani is optimistic about the potential implications the FDA’s approval of the HeartMate II as a bridge-to-transplant therapy could have on practicing cardiac surgeons and for patients.
“This is going to be the preferred device right off the bat,” Pagani said. “Traditionally, we waited until patients were in cardiogenic shock and really had organ dysfunction before we could justify putting the old pumps in. Now, with the risk profile of this device being better, people are going to start implanting this device earlier in the stages of advanced HF, and the outcomes are likely to be a lot better.” — by Eric Raible
For more information:
- To learn more about the HeartMate II, visit www.thoratec.com.
- Miller L, Pagani F, Russell S, et al. Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med. 2007;357:885-896.