Artificial Arteries Can Save Lives
By STEVEN M. SPENCER
Madison
Gay, a spry veteran of 40 years’ service in Birmingham, Alabama, steel mill,
squinted into the white-hot throat f a reheating furnace, then clanged the door
shut. He glanced at the gauges on the
control platform, turned a lever a few degrees, then stepped briskly to the
next furnace. His was not a job
requiring heavy physical exertion, but it was an active one for a man of 56 who
just 12 months earlier had had a segment of his most important heart artery,
the aorta, removed.
After
the operation Mr. Gay wora a new aorta of tough, braided nylon. This artificial trunk line artery, flexible
and non-kinking, carried blood from his heart to the lower part of his body,
replacing a section of his own aorta which had weakened and was about to burst.
For half
a century surgical researchers have been trying to find durable substitutes
with which to replace worn-out arteries.
They have used many things: metal, glass and plastic tubes, pieces of
patient’s own veins, arteries from deceased donors, strips of nylon petticoat
stitched into shape. Today this kind of
blood vessel ‘plumbing,’ using synthetic or donor spare parts, has become a
practical art. Several hundred thousand
people are now walking around with arterial grafts of one type of another
neatly and firmly sewed into their bodies.
The
grafts are replacing arteries which, because of injury, infection or ordinary
arteriosclerosis [hardening of the arteries], have become clogged or stretched
perilously thin. The stretching type of
damage, usually affecting the aorta, is known as an aneurysm. Ballooning out like a weak spot in the tire,
and aneurysm may burst at any time and let the victim hemorrhage to death.
The
clogging of occlusive type of circulatory impairment most often hits the
legs. At first it may cause only pain
on walking, but it can go on to gangrene and eventually amputation. In many male patients it also produces
sexual impotence.
Both
ailments are especially common in men from the age of 50 on, although women are
also affected. Of the two, aneurysm is
the more dangerous. For it may give no
advance warning, and when untreated it is rapidly fatal, with an average period
of survival of only one or two years after diagnosis.
Mr.
Gay’s trouble was an aneurysm of the abdominal segment of the aorta, a
complication of arteriosclerosis. His
physician discovered it when Gay went for a routine checkup in July 1956.
“He
found a mass in my abdomen that beat just like my heart,” Gay said. “I realized it had been there for some time,
but I hadn’t thought much about it.”
Within a
few days Gay was on an operating table having his dangerously swollen aorta
replaced with seven-inch length of sturdy nylon. The graft was branched at the lower end to connect with the two
main arteries supplying the legs. Six
months after the operation Gay was working full-time again. There were certain restrictions on him—he
was not supposed to lift anything heavier than five pounds, for instance—but,
as he said, at the time “I guess I’m lucky to be alive.”
In
contrast to the aneurysm, the obstructing type of circulatory disturbance
usually comes on slowly, over a period of months or years. Typical is the experience of an engineer
whose trouble started when he was 51.
He first felt a cramping pain in the right calf after walking a few
minutes. As time went on, the pain
struck more quickly and intensely, forcing him to stop and rest every half
block. As the relentless narrowing of
the blood-supply lines continued, the pain spread to the thigh, the hip, and
the lower back.
In the
engineer’s case, a nylon graft was inserted to by-pass the obstructed segments
of the blood vessels. Relief was
immediate. The patient was able to play
nine holes of golf regularly, and as a safety engineer for a gas company he
often miles along the pipelines.
The
generally discouraging results of medicine’s earlier efforts, plus the
widespread notion that hardening of the arteries is an irreversible consequence
of aging, created an almost fatalistic attitude toward the problem of
chronically impaired circulation.
Today, however, there is scarcely a spot along the main channels of the
body’s blood stream, which the vascular surgeons cannot reach for repairs. A patient’s age is no deterrent. I saw an aneurysm as big as a grapefruit
successfully removed from the abdomen of a man of 84. And many aneurysms have
been fixed days of grace by sealing off the break with clotted blood. A patient flown to Houston, Texas, from
Venezuela after his aneurysm had ruptured was saved with an artificial artery.
As a
matter of fact, Houston is the country’s busiest artery mending center. The vascular surgery group there, founded by
Dr. Michael E Debakey, professor of surgery at Baylor University College of
Medicine, has in the past five years installed more than 25,000 arterial
grafts. Most of these have been
homografts—donor vessels obtained at autopsy.
But since last spring Dr. Dena key and his fellow surgeons have used
synthetic arteries almost exclusively, believing that they are stronger and
more immune to re-invasion by arteriosclerosis patches.
A German
scientist, E Hopfner, in 1903, and the late Dr. Alex Carrel, of Rockfelelr
Institute for Medical Research, in 1905, made the first successful
transplantations of arteries—from one dog to another. But it was not until 1948 that artery grafting reached a
practical level, when Dr. Robert E. Gross, chief surgeon of Boston Children’s
Hospital, employed human grafts preserved in a special solution and
refrigerated.
Many
communities found the demand for donor arteries far exceeded the supply, however,
so the search for a strong synthetic artery continued. At Columbia-Presbyterian Medical Center, in
New York, Drs. Arthur H Blake more, Arthur B. Voorhees, Jr., and A. Jaretski,
III, tried a fine-woven Vinyon cloth, seemed to form a tube. Engrafted to a dog’s aorta, the tailored
artery was soon lined with a smooth, impermeable layer of the animal’s own
tissue cells. Encouraged, the surgeons
began, in 1953, to use the cloth artery in human patients.
When Dr.
Blake more described his Vinyon arteries at a Cleveland meeting in 1954, Dr. W.
Sterling Edwards, an assistant professor of surgery from Alabama Medical
College, wondered if these flabby cloth vessels could be given more body. Back in Birmingham he talked the problem
over with a patient, Pat Moore, an electrical engineer employed by the
Chemstrand Corp. in Decatur, Alabama.
Intrigued, Moore sold his company on the idea of developing a synthetic
artery. Since the commercial production
of such a product was outside its field, Chemstrand entered into the work on a
non-profit, public service basis.
Dr.
James S. Tapp, head of Chemstrand’s pioneering research section, reasoned that
braided tubing was a logical form for the artery. Nylon shoelaces are made of braided tubing. He ordered 250 yards of it. To give the tubing the required firmness he
dipped it in a solution of formic acid, a semi solvent for nylon. This also reduced porosity. To make it water resistant, he treated the
fabric with silicone.
Now Dr.
Tapp ordered the tubing in larger diameters—one quarter to three quarters of an
inch. But when installed in dogs’
aortas and in the groin of a human patient, the first nylon arteries kinked
when bent and shut off the blood flow.
This problem was solved by accident.
One day Dr Tapp pushed a length of braided tubing off a glass rod, the
tubing crinkled up in accordion pleats, as a paper wrapper does when removed
from soda straw. When he tried bending
the crimped tubing, it central passage stayed open. It was kink-proof.
Subsequent heat treatment gave the crimp a permanent set.
“We were
afraid the rough lining of the crimped tube would impede the blood flow and
cause clots,” Dr. Edwards says. “But we
hooked one up to the aorta of a dog, and it worked. In short time the dog’s tissues had given it a perfectly smooth
inner lining. “The crimping of the
synthetic artery also gave it stretchebility, important when a graft lies
across a knee of hip joint.
Surgeons
and patients now have a choice of arteries between braided nylon and knitted
Dacron. Dr. DeBakey has developed the
latter type with experts of the Philadelphia Textile Institute, who are turning
out Dacron arteries of a modified 40-year-old necktie-knitting machine.
My
blood-vessel operations are still major surgery. The occlusive type of impairment, such as the chronic clogging of
a leg vessel, demands careful evolution to determine whether or not an
operation is advisable. When the
trouble is an aneurysm, however, there is usually no hesitancy about
surgery. In the Houston group’s experience,
for instance, operative mortality on thoracic (chest) aneurysms now runs only 5
percent—although without surgery most of the patient’s die, and the 95 percent
saved constitute a tremendous salvage.
In abdominal aneurysm repair, the same surgeons have brought the
operative death rate down from 25 percent to less than 2 percent in the most
recent cases.
Surgery’s success in repairing worn-out or plugged-up
arteries has come only with a changing concept concerning arteriosclerosis, the
underlying cause of most circulatory derangements. Hardening of the arteries was formerly considered a generalized
and diffuse disease, not a condition which surgery could do anything for. Now surgeons have begun to realize that
arteriosclerosis is in many cases a local condition, segmental in
nature—something they can do a great deal about. Tremendous numbers of patients can be helped.
