sealPurdue News
____

September 27, 1991

Purdue conference takes new treatment to heart

WEST LAFAYETTE, IND. -- When it comes to heart muscle, patients may soon find that they are their own best donors.

Scientists working on a new technique -- cardiomyoplasty or plastic surgery of the heart -- will compare findings Monday (9/30) and Tuesday during an international conference at Purdue University.

The new procedure may prolong lives of people suffering from congestive heart failure and reduce the need for a transplants and artificial hearts. Instead, doctors use some of the patient's own muscle -- usually from the back -- to wrap around the heart. The muscle is then trained over a period of six to 12 weeks to contract simultaneously with the heart to help improve the organ's pumping capabilities.

"The muscle contracts around the heart at the same time the heart is beating, and in that way it can possibly help the heart's pumping function and prevent further heart enlargement," says Dr. Stephen F. Badylak, research associate with Purdue University's Hillenbrand Biomedical Engineering Center.

The group attending this Second International Conference on Cardiac Assistance with Skeletal Muscle will discuss two ways of using skeletal muscle to assist the heart.

The first method, cardiomyoplasty, is to move a muscle from the back and secure it around the heart. A special pacemaker is used to help the muscle contract simultaneously with the heart's contractions.

The procedure holds promise for a whole new area of cardiac treatment for people with chronic congestive heart failure, Badylak says. Patients with congestive heart failure have weakened heart muscles and lack sufficient pumping power to maintain adequate circulation of the blood.

Although still in early development, cardiomyoplasty is being used in clinical trials around the world. More than 12O patients have undergone the procedure, including a group of 15 U.S. patients who participated in early trials at Allegheny-Singer Research Institute in Pittsburgh.

This summer, the Food and Drug Administration approved five U.S. medical centers to perform a total of 5O additional procedures using the technique. The program is being coordinated by Medtronics Inc. of Minneapolis, which manufactures and controls the only FDA-approved pacemaker developed to work with skeletal muscle.

Patients will be selected for the procedure by the principal investigator at each institution, says Lori Austin, worldwide clinical manager for the cardiomyoplasty program at Medtronics. "Doctors are looking for candidates who are likely to survive surgery but who are currently not responding to drug treatments," she says.

Though the procedure may not become readily available for several years, Austin says the clinical trials are an important step in expanding the medical options for heart patients.

A second application for skeletal muscle is to use the muscle to construct a pouch that can act as an assist ventricle or secondary pumping chamber. In this technique, blood is pumped from the heart into the secondary chamber. During the heart's resting phase, the pouch contracts to pump the blood throughout the system.

Theoretically, an assist ventricle could increase the efficiency of the heart by 30-40 percent, Badylak says. Researchers around the world are testing different types of assist ventricles in animal models.

In spite of the success achieved so far, researchers agree that several challenges remain before the procedures can become widely available:

  • Optimizing surgical techniques. Researchers at Allegheny-Singer

    Research Institute are studying the best ways to wrap the skeletal muscle around the heart so patients can receive maximum benefits.

  • Training skeletal muscle to behave like heart muscle. Studies underway at Purdue and the Philadelphia Heart Institute are aimed at optimizing ways to train muscle to behave like heart muscle.

  • Finding suitable materials to line the assist ventricle pouch. Researchers at Purdue are testing other biological materials, such as selected body tissues, to help reduce the possibility of blood clots caused by synthetic materials.

  • Developing specialized hardware to work with skeletal muscle.

    Both procedures require hardware that can sense what the natural heart is doing, process the signal and then stimulate the skeletal muscle to contract in a very specific fashion, Badylak says.

    Purdue researchers have developed a new pacemaker that could be used to stimulate skeletal muscle wrapped around the heart. Another model has been designed to work with assist ventricles.

    Other research focuses on how skeletal muscle may be used to help patients with other heart-related ailments.

    Dr. James Sink, a cardiologist at the Philadelphia Heart Institute and one of a handful of U.S. physicians to receive approval from the Food and Drug Administration to perform the cardiomyoplasty procedure, is studying ways the technique could be used to help patients with ischemic heart disease, a condition marked by a deficiency of blood supply to the heart.

    The benefits of using a patient's own muscle are obvious.

    "Because the patient is his own donor, tissue rejection is eliminated," says David Farrar, vice president and director of Circulatory Support Products for Thoratec Laboratories Corp. "Also, there is no long-term reliance on anti-rejection drugs that can weaken the body's immune system."

    In addition, the new technique could be used to save the lives of patients awaiting donor hearts. "Though more than 50,000 people in the United States become candidates for heart transplants each year, only 2,000 operations are performed due to a shortage of donor hearts," he says.

    Though the use of skeletal muscle offers many advantages over traditional heart treatments, Badylak says these new techniques will not totally eliminate the need for heart transplants.

    "Like all other treatments, this will be done on a case-by-case basis," he says. "There is no single treatment that is best for all patients."

    Purdue News Service: (765) 494-2096; purduenews@purdue.edu

    		•