Tiny Implantable Pump Assists Dying Hearts

From the WebMD Archives

April 20, 2000 -- In a Houston hospital, a device that?s about the size of a C battery is pumping life-saving blood through the veins of woman who just a few weeks ago was struggling for every breath. The tiny heart pump is the latest medical wonder from the mind of Robert K. Jarvik, MD, who almost 20 years ago stunned the world with his Jarvik 7 mechanical heart.

Unlike the media circus that surrounded Jarvik in Salt Lake City when he implanted his earlier device in patient Barney Clark, news about the latest breakthrough is being tightly controlled. So far the Texas Heart Institute and St. Luke's Episcopal Hospital, where the surgery was performed on April 10, have released only a brief statement.

The FDA is giving Jarvik the go-ahead to test his new pump in a small group of critically ill patients, but John Stuhlmuller, MD, of the FDA's device committee tells WebMD that "by law we cannot comment on this application."

The press release from the hospital says the Jarvik 2000 is a valveless, electrically powered miniature axial flow pump that fits directly into the heart's left chamber, called a ventricle, and pushes oxygenated blood throughout the body.

What is known is that the device is a rotary type pump, much like the water pump found under the hood of a car or the pumps used in aquariums, says William Smith, PhD. Earlier pumps, like the Jarvik 7, used piston-like pumping mechanisms that mimic the heart's natural pumping action, he says.

The pump works by spinning a blade, called an impeller, on an axis. This spinning motion first draws blood into the left ventricle of the heart and then forces it back out, says Smith, who is designing several similar devices. Smith, a biomedical engineer, says he has been involved with mechanical or artificial heart research for 18 years, and that he has seen data on the Jarvik 2000.

The device is "... only pumping a few liters a minute and only at about two-thirds of normal arterial pressure, so it does require that the natural heart still have some function, which most hearts do have," he tells WebMD.

Rotary pumps are somewhat controversial because they provide continuous blood flow -- leaving the patient without a pulse -- and it is unknown if this continuous flow would have an effect on the body, says Smith. However, a Cleveland Clinic surgeon implanted one such device in a patient as a way to help the patient's heart prior to a donor heart becoming available for transplant, he says, and "it was implanted for 30 days, and the patient had no apparent ill effects."

Dale Renlund, MD, professor of medicine at the University of Utah School of Medicine, says he has no idea what effect, if any, a continuous flow would have. He says the experience in Cleveland is interesting but "one patient doesn't prove anything."

Renlund says the news about the Jarvik 2000 pump is very encouraging. "Even if the Jarvik 2000 can only pump as little as 3 liters per minute it's terrific because a lot of patients could be sustained on just 3 liters per minute and could preserve vital organs," he says. "The axial flow pumps hold great promise because it is really straightforward, simple technology that is really quite ingenious and might be better than anything else."

Acknowledging that he and other Cleveland Clinic researchers are obvious competitors to Jarvik, Smith nonetheless says he is encouraged by the success of the Jarvik 2000 implant. The clinic has made a conscious decision to "not just pursue one device, because we think patients need a variety of devices. The Jarvik 2000, for example, is a potentially wonderful pump for a certain niche of patients, but there are tens of thousands who will need something else."

Now, people with end-stage heart disease have very few options. They can have transplants, but with 60,000 to 80,000 patients waiting for about 2,000 donor hearts available per year, that is not an option for most patients, Renlund says. Another option is permanent mechanical support, and that option is being studied now in a trial that compares permanent mechanical support to medical therapy.

Vital Information:

  • Researchers have developed a tiny, mechanical heart pump called Jarvik 2000, and it is currently undergoing the early stages of testing.
  • The device is about the size of a "C" battery and works like a rotary pump, sending blood through the heart.
  • Patients with heart failure have limited treatment options, so the use of implanted mechanical devices is becoming more common for patients waiting for a transplant.