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WASHINGTON, Aug. 29 -- A left-ventricular assist device that provides a steady rather than a pulsed blood flow may serve as an effective bridge to transplant, found a multicenter team.

Among 133 patients with end-stage heart failure who had received the HeartMate II LVAD prior to transplant, 75% of those who remained on the device survived with it for six months, and 68% survived with it for one year, revealed Leslie W. Miller, M.D., of MedStar Health here, and colleagues in the HeartMate II trial.

At three months, the device was associated with improved functional status and patient quality of life, the authors reported in the Aug. 30 issue of The New England Journal of Medicine.

"We found that this device provided effective mechanical circulatory support in patients with refractory heart failure," the investigators wrote. The device is powered by an external controller worn on a belt and battery packs on a shoulder holster.

But as with other cardiac-assist devices, the axial-flow pump was also associated with significant risk of bleeding, ischemic and hemorrhagic strokes, right heart failure, and infections related to the percutaneous leads, the authors noted.

The HeartMate II (Thoratec) contains an inflow cannula inserted into the apex of the left ventricle, an outflow cannula that is connected by anastamosis to the ascending aorta, and a rotary impeller pump (the only moving part) placed within the abdominal wall or peritoneal cavity.

As blood exits the left ventricular apex, it enters the inflow cannula of the device which draws blood through the device and pumps it throughout cardiac diastole and systole into the ascending aorta.

Axial-flow pumps are well-suited for use in heart transplant candidates who may need a bridge to transplantation allowing functional recovery with or without hospital discharge, noted Kenneth L. Baughman, M.D., of Harvard, and associate editor of NEJM, and John A. Jarcho, M.D., deputy editor of the journal, in an accompanying article on advances in heart-support technology.

The devices are smaller than the older pulsatile-flow LVADs, and because they contain only one moving part, may be less susceptible to mechanical failure, Dr. Miller and colleagues wrote.

They studied the use of axial-flow pump in a prospective trial in 133 patients who were on a transplant waiting list.

The primary study outcome was the proportion of patients at six months who had either undergone transplantation, had cardiac recovery, or continued on mechanical support while remaining eligible for transplantation. They also looked at New York Heart Association functional status and patient quality of life as assessed by the Minnesota Living with Heart Failure and Kansas City Cardiomyopathy questionnaires.

They found that the 100 patients (75%) reached the principal outcomes of transplant, cardiac recovery, or survival at 180 days with ongoing mechanical support and eligibility for transplantation. In all, 56 of the 100 patients had a transplant, 43 remained on support and were eligible for transplant, and one had recovery of cardiac function and removal of the device.

Twenty-five of the remaining 33 patients died before 180 days of support, with a median time to death of 38 days (range six to 144 days). The causes of death included sepsis in five patients, ischemic stroke in five, multisystem organ failure in four, hemorrhagic stroke in three, anoxic brain injury in two (one after a protamine reaction and one after a hemothorax with cardiac arrest), right heart failure in two, and various causes in four.

There was one device-related death that occurred when an inflow graft was accidentally twisted during implantation, the authors wrote.

Five additional patients became ineligible for transplantation during mechanical support because of irreversible medical complications, and three patients had replacement of the continuous-flow pump with a different type of ventricular assist device because of surgical complications (these patients were withdrawn from the study).

"Most patients who were evaluated at three months after device implantation had improvement in at least two NYHA functional classes and improvement in a six-minute walk test by a distance of more than 200 m," the authors wrote. "Measures of quality of life significantly improved after device implantation on the basis of both survey instruments used (P

The most common non-fatal adverse event in the study was bleeding, which occurred primarily in the early postoperative period. Bleeding requiring surgery occurred in 31%, and 51% of patients had bleed episodes that required only the use of two or more units of packed red cells. Ischemic stroke occurred in eight patients (6%), and hemorrhagic stroke occurred in three (2%). Five of the 11 strokes occurred within 48 hours of device implantation. Five patients had transient ischemic attacks that were completely reversed.

Five of the devices needed to be replaced: two for pump thrombosis at 24 and 56 days after implantation, and three for complications related to surgical implantation at one, 15, and 32 days.

"Although continuous-flow pumps may have some advantages over pulsatile pumps . . . the devices also pose new or continuing challenges related to the treatment of patients," the authors wrote. "These issues include the risk of pump thrombosis and thromboembolism, with the requirement for higher levels of antithrombotic therapy than are required for some pulsatile devices and a consequent risk of bleeding. Infection remains a potential concern, as with all circulatory devices that have a percutaneous component."

In their accompanying perspective, Dr. Baughman and Dr. Jarcho called for clinical trials pitting specific ventricular-assist devices against one another.

"Such trials, appropriately designed, would be a tremendous asset in enabling physicians and patients to make informed decisions about the most appropriate device for severe heart failure," they wrote.

Dr. Miller and colleagues noted that the study was limited by the lack of concurrent controls, the inability to assess functional status and quality of life in all study patients, and difficulties in comparing their findings with those of other groups due to "somewhat subjective" patient selection criteria.

The study was supported by Thoratec, maker of the LVAD studied. Supported by Thoratec, Dr. Miller and several co-authors reported receiving consulting and or lecture fees from the company and other makers of cardiac assist devices. Co-author David J. Farrar, Ph.D., is an employee of Thoratec and has an equity ownership in the company.

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