Science / Medicine : Tiny, Experimental Pump Offers Hope for Heart Patients

For decades, heart surgeons have experimented with, and fantasized about, man-made devices that can replace the workings of the human heart. Recently, in a Houston hospital, a new type of artificial heart pump was used on a human patient for the first time. Radically different from other heart substitutes, the new pump is about the size of a pencil eraser and does not require opening of the chest to be inserted. Rather, doctors feed the device into the heart’s left ventricle through an artery in the leg.

Nor does the new device employ a “beat,” as does the heart. Once implanted, a tiny turbine spins at 25,000 revolutions per minute to pull blood from the patient’s ventricle and send it coursing throughout the body in a steady stream.

Since the Houston experiment, which was successful, the hemopump has been tried on four additional patients. Each of the recipients was seriously ill with a heart condition that was otherwise regarded as terminal. Two of those patients eventually succumbed to their disease but two recovered, and the heart pump was judged to have performed well in all the experiments.

If further testing proves equally successful, it will likely be approved for general use by the U.S. Food and Drug Administration in about 18 months. When that happens, medical researchers believe that the Hemopump could make important changes in the way some heart patients are treated.

The Hemopump has been a dream of the inventor, Dr. Richard K. Wampler, for many years. The director of medical affairs at Nimbus Medical Inc. of Rancho Cordova, Wampler pursued his design through a long series of setbacks and frustrations. The following is the story of the Hemopump’s invention, as told by Dr. Wampler.

I was a surgical intern when my imagination was first touched by the vision of a patient, beyond all hope, being returned to life by some mechanical power pumping his life’s blood. It seemed like a miracle, and the idea of creating such a device took me over. Soon I found myself drawing prototypes in my off hours, dreaming and planning. In the shower an idea would come to me and I would run soaking wet for a scrap of paper to jot down a fading image.

That was more than 10 years ago and not much came of it. I think I was frightened by the size of the challenge, and I hung back. But the idea never left me, and when I came to work at Nimbus--about six years ago--the project was revived. This time, of course, I had the support of a company whose business is the development of new medical equipment.

There was a practical reason for Nimbus’ interest, and mine. The standard approaches to artificial heart pumps have always been very invasive to the human body. You have to open the chest, cut into the heart and then make another cut into the aorta. It’s a major surgical procedure, with all the trauma and risk that implies.

The pump I wanted to create would not have those drawbacks. It would be small enough to insert without surgery, would not require blood to be brought outside the body, and would work without cutting into the heart.

The seed for the idea came from my own personal history. In the early 1970s, I volunteered to work in a rural Egyptian village, helping out with development projects. It was my job to find a solution for their water supply problem. I learned about deep wells and submersible pumps. This knowledge was to be the last piece of the puzzle when I conceived of the Hemopump.

At Nimbus, I decided the heart pump problem was similar in many ways to the Egyptian well problem. Each pump had to be submersible and the task involved pulling a liquid from one remote reservoir and moving it somewhere else.

In the beginning there was considerable doubt about the feasibility of using a turbine to pump blood. No one had done it before, largely because of the fear that the turbine blades would act like a blender and damage the red blood cells in a process known as hemolysis.

We came up with several designs that worked perfectly in the laboratory, but when the pumps were used in animal experiments the tiny seal at the base of the turbine propeller would quickly fail and the turbine would break down.

It was maddening. We would watch the turbines seize up and didn’t know what was going wrong with the seal. For a while this tiny part of the design threatened the entire project.

Eventually, slowly, the problem was solved by adding a miniature flushing system that kept debris from building up inside the pump. There were other problems, but one by one they were solved and finally we arrived at the day of the first human test. In Houston, my biggest worry was whether we could make the insertion of the device successfully. The pump is implanted by opening the femoral artery in the leg and feeding it upward to the heart. Since we had never done it before on a human, we didn’t know if plaque build-up in the arteries would block the device. We had made plenty of insertions in cows but you just don’t find cows with hardening of the arteries.

As it turned out, the insertion was easy and only took about half the time we had anticipated.

And so far, at least, there have been no major problems with the pump. I say this with some sadness because two of the patients died in spite of the help offered by the Hemopump. But in a patient group in which nine out of 10 die we have saved three out of five. According to the rules of our research, only patients who are very close to death can be considered candidates for the pump’s use and it should be expected that some won’t make it--if the heart is dead, nothing can cause it to beat again. We do know that the Hemopump did everything expected with all the patients and was not a contributing factor in the deaths.

We think the Hemopump has an exciting future. We are learning that the human heart can recover a great deal of its ability to beat after a heart attack--if it is just given a chance to rest. Doctors once thought that heart muscle was destroyed by a major heart attack; now we know that, in many cases, the muscle is just damaged or stunned and can heal itself in a few days if rested.

I remember once, during the Hemopump’s development, I was in a movie theater and the fantasy of every doctor occurred. Suddenly the manager called out, “Is there a doctor in the house?” I jumped up, and it turned out a man had suffered a serious heart attack in the restroom. His skin had the blue-gray color of death and he kept saying, “Help me, I can’t breathe.” I had no supplies, no equipment. I did everything I could but realized he was slipping away. Desperately, in my mind, I wished that I could reach for a Hemopump and save the man’s life. I couldn’t that night, and the man later died.

With the development of Hemopump, such a lifesaving procedure may someday be possible.

Building a heart pump The Hemopump is different from most artificial hearts in that it does not ‘beat’ and does not require a surgical openint of the chest. Doctors cut through an artery in the leg, threading the tiny device into the left ventricle of the heart. Once implanted, a tiny turbine spins at 25,000 revolutions per minute to pull blood from the patient’s ventricle and send it coursing throughout the body in a steady stream.