LOS ANGELES – Some patients with a total artificial heart can safely go home with the use of a small portable driver while awaiting heart transplantation, according to data from the first U.S. patient cohort in whom this was attempted.
Investigators assessed outcomes in 13 total artificial heart recipients who were stable enough clinically to be transitioned from the usual driver to SynCardia Systems’ investigational portable driver, the Freedom Driver System. The driver weighs 14 pounds and allows several hours of untethered activity.
Eight of the patients were able to go home for an average of 5.5 months, lead investigator Dr. Vigneshwar Kasirajan reported at the annual meeting of the Society of Thoracic Surgeons.
Dr. Vigneshwar Kasirajan
They had a low rate of major bleeding and no major infections. There were roughly five device malfunctions per patient-year, but in all cases, patients were able to switch to a backup driver uneventfully.
Twelve of the 13 total patients ultimately underwent transplantation, for a transplantation rate of 92%.
"The Freedom driver is effective in supporting circulation with a total artificial heart. Discharge home is safe and feasible," commented Dr. Kasirajan, who is director of heart transplantation, heart-lung transplantation, and mechanical circulatory support at Virginia Commonwealth University in Richmond.
"Further data on the completion of this study will help to demonstrate the efficacy and safety of the driver. In addition, important data on exercise capacity and quality of life will be valuable in finally moving the artificial heart technology to more widespread use," he said.
Session comoderator Dr. Todd M. Dewey, a cardiothoracic surgeon with Medical City Specialists in Dallas, noted, "The majority of patients on axial-flow left ventricular assist devices are discharged home. What percentage of total artificial heart patients do you think will ultimately leave the hospital?"
"We are close to 80% of our patients going home right now, at least in high-volume institutions," Dr. Kasirajan replied. Two patients have been at home for more than 2 years without readmissions related to the device, he added.
A pivotal study previously showed that the total artificial heart can be used as a bridge to transplantation in patients with irreversible biventricular failure (N. Engl. J. Med. 2004;351:859-67).
"Unfortunately, ... the widespread use of this technology is limited because of the inability to discharge these patients home, and that relates to the fact that the circulatory support system console has to be powered by compressed air either from the hospital or via a cylinder," Dr. Kasirajan explained.
However, once patients are stable, the driver settings need little adjustment, which spurred development of the portable driver. "The driver has two batteries that allow up to 3 hours of untethered activity. These can be charged in place using an alternating current output or car charger," he said.
The ongoing study of the driver will enroll up to 60 patients from 30 international sites. Patients are required to be wait-listed for heart transplantation and receive a total artificial heart, and to be clinically stable on the circulatory support system, with a cardiac index of at least 2.2 L/min/m2. They are then switched to the portable driver with the intent of discharge from the hospital.
Dr. Kasirajan reported results for the first 13 patients enrolled from four U.S. sites. Overall, 5 of the patients remained in the hospital (because of medical reasons, discharge logistics, or personal preference), whereas 8 went home with the driver. The median duration out of the hospital in the latter group was 162 days (range, 39-437 days).
The 13 patients had maintenance of cardiac function, with a cardiac index averaging 3.3 L/min/m2, and their laboratory values remained stable between baseline and 90 days. "Particularly, there was no evidence of hemolysis that was worse than at the beginning," he noted. "Increasing albumin levels reflect the increasing nutritional status in these patients."
The in-hospital group had a very similar rate of adverse events relative to an earlier comparison cohort of stable patients with a total artificial heart followed as part of postmarket surveillance, according to Dr. Kasirajan.
Within the study population, the out-of-hospital and in-hospital groups had similar rates of major bleeding (1.1 vs. 1.4 events per patient-year). The former had a lower rate of major infection (0 vs. 2.8 events per patient-year) but higher rates of device malfunction (4.6 vs. 0 events per patient-year) and hemolysis (2.3 vs. 0 events per patient-year).
The five device malfunctions in the out-of-hospital group were due to a Valsalva maneuver, a faulty sensor, hypertension, a kink in the driveline while a patient was getting into a car, and dropping of the driver while showering.