The FDA action made AbioCor, developed by Abiomed, Inc. of Danvers, Mass., the first replacement heart to gain approval.
Only patients who have advanced heart failure that has affected the left and right ventricles and who are not candidates for a heart transplant will be eligible to receive the device under the agency's Humanitarian Use Device provisions.
Daniel Schultz, M.D., director of the FDA Center for Devices and Radiological Health, said the approval marked at "a significant advance in artificial heart technology and holds promise for critically ill heart patients who are not candidates for heart transplants due to age or other medical conditions."
The AbioCor system consists of: a two-pound mechanical heart that takes over the pumping function of the diseased heart, which is removed during the implantation procedure. Chest cavity size is a consideration for patient selection, so the device is not suitable for pediatric patients.
It is powered by a transcutaneous system in which a transfer coil placed on the skin not only powers the system but can also recharge the internal battery. The transcutaneous power system allows the patient mobility without being tethered to a power source, which was a drawback of earlier mechanical hearts.
At night the system can be powered by plugging into an electrical outlet.
Devices approved under the humanitarian provisions are those intended to treat conditions or diseases that affect fewer than 4,000 people a year. Similar to the Orphan Drug Act, the humanitarian provisions were designed to encourage development of innovative medical devices for rare conditions.
In June 2005, an FDA advisory panel voted seven to six against approval of the AbioCor device. That panel evaluated the same data cited by Dr. Schultz when he announced the approval-animal studies and a 14-patient clinical trial.
All 14 patients who received the heart died, two during surgery. The average survival was 138 days, but one patient lived for 512 days and was able to be discharged from the hospital.
Abiomed said in a statement that it is limiting use of the device to surgeons in three hospitals-Jewish Hospital/University of Louisville, Johns Hopkins in Baltimore, and Robert Wood Johnson University Hospital in New Brunswick, N.J.
Laman Gray, M.D., and Robert Dowling, M.D., are the Louisville surgeons who implanted the first and second AbioCor hearts, both procedures done 01.
Dr. Schultz acknowledged that the mechanical heart is not an ideal solution for all eligible patients, but said that "for many patients faced with death, the chance to have additional time with family and friends-however limited-is a chance they are willing to take."
Elizabeth G. Nabel, M.D., director, of the National Heart, Lung, and Blood Institute, which has helped fund the development of an artificial heart, praised the FDA decision, which she said represented "a major technological advance and will benefit people in critical need."
The FDA approval came during a week when heart devices have come under renewed scrutiny triggered by news of a possible increased risk of thrombosis with drug-eluting stents.
And estimated six million Cypher (sirolimus-eluting) and Taxus (paclitaxel-eluting) stents have been implanted worldwide. On Sunday two studies at the European Society of Cardiology/World Congress of Cardiology in Barcelona reported that the Cypher stent had a significantly higher risk of cardiac and non-cardiac death and non-fatal myocardial infarction than bare metal stents.
Those studies did not find a significant increase in risk for the Taxus stents compared with bare metal stents and during the Barcelona meeting Boston Scientific, which makes the Taxus stent, maintained there was no significant increase in long term risks with its stent.
Today, the company acknowledged that there was a small but significant increase in thrombosis risk with its stent. It said it had presented data indicating this to the FDA in August.
The stent controversy puts the AbioCor approval in an interesting context. During clinical trials the mechanical heart had problems with both excess bleeding and blood clots, problems typical of any implanted devices.
For heart devices, the risk continues as long as its surface area is not re-endothelialized. Bare metal stents are endothelialized in less than 30 days, so dual antiplatelet therapy with aspirin and Plavix (clopidogrel) is recommended for 30 days.
The drugs released by the Cypher and Taxus stents block neointimal hyperplasia, which also blocks the re-endothelialization process, so dual anticoagulation is longer. For Cypher the minimum recommendation is six-months of Plavix and aspirin, and for Taxus it is three months.
But the American College of Cardiology/American Heart Association guidelines recommend that patients who have no excess bleeding risk be kept on Plavix and aspirin for 12 months and aspirin for life.
Thus far there are no guidelines on anti-coagulation for patients who receive the AbioCor mechanical heart, but they will require both anticoagulation and infection control, according to published data on the AbioCor clinical experience.
- Reviewed by Zalman S. Agus, MD Emeritus Professor at the University of Pennsylvania School of Medicine