Implantation of the world's first AbioCor replacement hearts may be grabbing all the headlines, but other medical device companies are quietly tinkering with left-ventricular-assist systems in an effort to gobble up their share of an as-yet-undetermined market.
A generation in development but on the fast track in recent years, ventricular-assist systems serve as life-support systems for patients waiting for heart transplants. Through mechanical means, they provide part or all of the pumping action of the left ventricle; when a patient suffers from congestive heart failure, the left ventricle most often fails.
In contrast, the AbioCor artificial heart involves removing all of the natural heart, making it a lifesaver for those who have lost all hope of any kind of recovery.
Both devices have been downsized. The AbioCor, made by Danvers, Mass.-based Abiomed, is portable and considerably smaller than first-generation artificial hearts of a decade ago. Ventricular-assist devices also have shrunk in size the past several years, allowing patients suffering from congestive heart failure who are waiting for transplants to lead semi-normal lives.
And despite the Food and Drug Administration's limited approval of ventricular-assist devices as a bridge to transplant, stories abound of patients surviving months to years on the devices. For example, in promotional literature, World Heart Corp., Ottawa, Ontario, Canada, shows a picture of a man swinging a golf club 217 days after implantation of its Novacor ventricular-assist device. He is wearing a vest with pockets for the device's battery and accessories.
The relatively long-term success of some ventricular-assist devices raises questions about using them as treatment for patients ineligible for transplants or those who simply need time to give their diseased hearts a chance to rest and recover.
Next week, the devices may move closer toward that goal. Results of a clinical trial of ventricular-assist devices will be presented at the annual meeting of the American Heart Association and published in a still unnamed peer-reviewed journal. The study pitted the experience of patients who were solely supported by HeartMate VE, developed by Thoratec Corp., Pleasanton, Calif., against that of patients being treated with traditional drug therapy and medical management.
Led by Eric Rose, M.D., chairman of surgery at Columbia Presbyterian Medical Center, New York, the randomized trial encompassed 20 clinical sites and 128 patients with end-stage heart failure. If the trial results tip the scales in favor of ventricular assist over drug therapy, it will bolster Thoratec's application to the FDA for expedited approval of HeartMate as a long-term support device for heart failure patients not eligible for heart transplants.
Thoratec plans to market HeartMate for that long-term indication by mid-2002, says D. Keith Grossman, Thoratec president and chief executive officer. "The bridge-to-transplant market has grown, but the real future use is in bigger patient populations who are not transplant candidates and not getting on the heart-transplant waiting list at all," he says.
There is significant disagreement about the size of this market.
Roderick Bryden, World Heart's president and CEO, says that each year there are 500,000 new cases of heart failure in the U.S. and 250,000 patients who die from it. Meanwhile, he says, only 2,500 hearts are available for transplant annually. About 85% of the patients suffering from heart failure have problems with their left ventricles, leaving at best 15% of the congestive heart failure market for Abiomed's artificial heart, he says.
Grossman says he believes Thoratec now claims as much as 90% of the market, estimated at $100 million in 2000. However, that total was for the use of the devices as a bridge to transplant only. "We're just barely getting started as far as (ventricular-assist devices') potential," he says.
According to Thoratec, each year some 150,000 patients have acute but recoverable heart failure. Another 100,000 patients suffer from late-stage heart failure with no hope of recovery.
Grossman is even less generous in what Abiomed's share of that market would be: 5% or less of late-stage heart failure patients. "It's a very high bar to clear technologically for a small group of patients," he says.
Abiomed takes issue.
Edward Berger, Abiomed's vice president of strategic policy and planning, cites data from the National Institutes of Health that attributed 45,000 deaths last year to congestive heart failure, but nearly 10 times as many deaths-400,000-from coronary heart disease. Some of those patients might be candidates for replacement hearts as well.
"If you are going to be comparing market sizes, talk about share of the congestive heart failure market is one thing, but it would be an error to say there is a bigger market for (ventricular-assist devices) than replacement hearts," Berger says.