After 23 years of trial-and-error research to develop a cardiac pacemaker powered by the body`s own energy, biophysicist Carl Enger remains undeterred.
And now the 56-year-old Boca Raton-area scientist believes he may have found the solution to the problem he set for himself decades ago.
Enger, who was a pioneer in the development of the pacemaker, says he has found a way to use body heat to generate enough electricity to operate a pacemaker indefinitely.
The miniaturized pacemaker Enger envisions will be about a quarter-inch thick and no bigger than a 50-cent piece. As the technology advances, the pacemaker may be reduced to the size of a quarter and weigh less than two-tenths of an ounce, he said.
Some conventional pacemakers weigh close to five ounces.
And unlike conventional pacemakers whose batteries must be replaced surgically, Enger says his device ``will last the life of the patient.``
``The patient wouldn`t really know it`s there,`` he said.
The smallest battery-powered pacemaker that has been developed is about the size of a silver dollar. The first one was implanted Oct. 2 in a 77-year-old Fort Lauderdale woman at Holy Cross Hospital.
Pacemakers are implanted in the body to provide a regular, measured amount of electrical current to the heart to maintain a steady beat when the muscular pump`s own pacing cells malfunction.
Since the devices came into general use about 25 years ago, more than 500,000 people have received them, according to the American Heart Association.
There are now about 5,700 heart surgeons and cardiologists who are implanting pacemakers at 3,300 hospitals, the Heart Association estimated.
The heart problems corrected by pacemakers include irregular heartbeats, heartbeats that are too fast or slow or even the complete failure of the heart to beat.
Doctors have known since the 18th century that electricity can stimulate the heart. The use of electrical stimulation to revive patients began in earnest in 1929. By 1933, a physician had patented a device he called a ``pacemaker.``
The first wearable pacemaker was developed in 1958 to pace patients after open-heart surgery. Two years later, an implantable pacemaker had been developed which was about the size of an adult heart.
Pacemakers usually are implanted in a simple operation by threading electrode-tipped wires through a vein in the patient`s chest to his heart. The wires are attached to the pacemaker which is placed into a surgically created ``pocket`` usually under the patient`s arm.
Continuous improvements have been made both in the batteries energizing the pacemakers and in the electronics that meter the power to the heart.
The more sophisticated pacemakers can tell if the heart is beating normally and turn itself off when it is not needed. Other devices can sense how hard the body is working and adjust the heartbeat accordingly.
Even though very little electricity is needed to power a pacemaker, the mercury-zinc batteries that were used initially lasted less than two years. The newer lithium batteries now in use have a life expectancy of five to 10 years.
Still, according to a 1983 Heart Association study, about 21 percent of pacemaker operations are done to replace exhausted batteries or to correct other problems with the devices.
Edwin Duffin, a senior researcher for Medtronic, Inc. of Minneapolis, the largest manufacturer of pacemakers, said that discovering a permanent power source for pacemakers has ``long been the obvious thing people have wanted to do. These have been worked on on and off for many years.``
But problems with materials that would not supply enough power or that would be toxic if placed in the body have hampered development of self-powered pacemakers, Duffin said.
Instead, industry researchers have concentrated their efforts on refining the lithium batteries, devising more sophisticated electronics for pacing the heart and making pacemakers cheaper and more reliable, he said.
Nevertheless, said Duffin, ``(Enger) may be on to something. It`s hard to say what the odds are.``
Enger is carrying on his research -- doing the ``bench tests`` on his new pacemaker -- in a makeshift laboratory filled with electronic gear in a spare room of his house.
The technology for the ``solid state thermal junctions`` which will power the pacemaker has been around for a number of years but has never been applied to a medical device.
Only recently has it been possible to apply the techniques used to make computer memory chips to miniaturize the thermal device sufficiently to implant it in people.
Miniaturization will be a costly process, according to Enger. He plans to conduct initial laboratory tests on larger versions of the power source before shrinking it to the size where tests on animals and people can begin.
There have been several attempts at making a pacemaker that could work long periods without batteries -- including a device powered by radioactive isotopes -- but none has been successful enough to put into general use.