NEW YORK-Cardiac medicine is homing in on a long-sought goal.
An advanced total artificial heart-the AbioCor Implantable Replacement Heart (ABIOMEDTM)-is ready for clinical trials, researchers told an international conference here on circulatory-support devices. And scores of patients in trials have already been implanted with CardioWest's successor to the Jarvik 7.
Abiomed's device will be the first total artificial heart (TAH) to free patients from skin-piercing cables connecting them to an external power source. Instead, a wearable external battery will transfer energy across the skin to a rechargeable internal battery.
It will be several years before AbioCor is available commercially, but trials should begin in 2001. Meanwhile, CardioWest is asking the FDA to approve its TAH as a bridge to transplant. Both procedures involve removing diseased heart ventricles.
The CardioWest device is pneumatically driven. It has polyurethane ventricles with cuffs that are sutured to the atria in a four-to-six-hour implantation procedure and a GoreTex membrane to prevent adhesion to the lungs and chest wall.
The device works well, researchers say. In one study of 24 recipients, all but two progressed to transplant and 20 survived, while only seven of 18 controls made it to transplant and three survived. But it's cumbersome. Though a suitcase-sized battery is in development, for now patients are attached to the device by percutaneous wires and an eight-foot-long tether attached to a 350-pound air pump the size of a washing machine.
Tucson cardiac surgeon Jack Copeland, whose team has implanted 53 CardioWest TAHs, considers it the device of choice for patients with rapidly decompensating biventricular function who fail to respond to maximal medical therapy.
Worldwide, 175 patients have been on a CardioWest TAH for one to 318 days (average 45). But the device has limitations, Dr. Copeland points out. It doesn't fit in all patients and requires a strict anticoagulation regimen postop. Its percutaneous wires can cause infections, and patients have had a 17% mortality rate.
The device costs $42,500 but with the console, other equipment, and hospital care, the procedure runs to about $300,000. That will drop when the portable battery comes on line, says CardioWest's Dr. Francisco Arabia.
AbioCor is the product of a National Heart, Lung, and Blood Institute research program set up more than a decade ago. The goal was to develop a completely internal TAH that would run for at least five years.
Four groups won contracts for the studies but only two were continued- Penn State/Hershey Medical Center's and Abiomed's.
In September, Abiomed acquired rights to the Penn State device. Penn State's Dr. Gerson Rosenberg sees them going to patients who need biventricular support but who will not be eligible for transplants.
Penn State emeritus surgery professor William Pierce, a pioneer in the field, says he's confident that with Abiomed, "we will succeed much faster in achieving cardiac medicine's goal of replacing the failing human heart."
The AbioCor device will give patients more freedom of movement. Not much bigger than a real heart, it weighs two pounds. It consists of a thoracic unit, containing the ventricles with their valves and the pumping system, and internal lithium batteries that are recharged by external batteries via a skin transformer.
The beauty of the power system is that the internal battery can hold a charge for 30 minutes, freeing patients to shower or perform other activities-even swim.
The "brain of the heart," an electronics package implanted in the patient's abdomen, monitors and controls the TAH performance, including the pump speed so that it automatically responds to physiological demands.
AbioCor has been tested in over 100 calves but just for a few months since the animals quickly outgrow human-size hearts. Clinical trials will soon begin at the Texas Heart Institute, UCLA Medical Center, Brigham and Women's, Mass General and Hahnemann hospitals, and the Jewish Hospital Heart and Lung Institute in Louisville.
When AbioCor wins FDA approval, a patient implanted with one will have a quiet device with no percutaneous wires that raise the risk of infections, says Abiomed's president Dr. David Lederman. In addition, recipients will likely require minimal medication.
When production quantities of the device reach thousands of units, Dr. Lederman estimates the price will come down to about $25,000. He estimates the five-year cost of a mature AbioCor will approximate $125,000 including surgery and batteries.
Not everyone thinks a TAH will be the global solution to endstage heart disease. Cleveland Clinic cardiothoracic surgeon Patrick McCarthy says he thinks TAHs will help only 5,000 to 10,000 patients a year, while very small, magnetically suspended LVADs now in development could benefit 70,000 recipients annually.
On the other hand, Tennessee State U's Dr. D. Glenn Pennington, who chaired the recent conference, says he's enthusiastic about TAHs.
Abiomed's goal is to make a TAH with a five-year lifespan-a small fraction of the longevity of a normal heart, but quite a reprieve for a patient with heart failure. "It's like flying. The first planes were not expected to fly around the world," says Dr.
Lederman. -Elsie Rosner
NEW YORK-Cardiac medicine is homing in on a long-sought goal.
