DURHAM, N.C. -- Using high-powered lasers to pierce new blood-carrying
channels into ailing heart muscle, Duke University Medical Center heart
surgeons are testing a promising new therapy for patients with coronary
artery disease who have exhausted all other conventional forms of treatment.
Duke is the only medical center in the Southeast using the laser system,
which has demonstrated promising results for the eight patients treated
at the medical center since October.
"The laser gives us another tool for helping patients for whom we
could do nothing else," said Duke surgeon Dr. James Lowe, who heads
up the Duke investigation. "These patients typically have had multiple
hospital admissions, they can't work or exercise and physical exertion of
any kind causes crushing heart pain (angina). They are a tragic and unhappy
group of patients because they are so incapacitated and we can do very little
for them."
Duke and 12 other U.S. medical centers are conducting clinical trials of
The Heart Laser, which was developed by PLC Medical Systems Inc., Milford,
Mass. The company recently was granted expedited review of its premarket
approval application for the Heart Laser by the U.S. Food and Drug Administration
(FDA). To date, more than 350 patients have undergone the procedure in
the United States.
The procedure, known as transmyocardial revascularization (TMR), opens
new passageways in heart muscle that is still alive, but because of inadequate
supply of blood, is not functioning properly.
"The patients we have treated with TMR have seen an average 80 percent
decrease in their angina score after three months," Lowe said. "When
we compare the scans of their hearts before the procedure and after three
months, we can clearly see that more of the heart muscle is oxygenated and
functional."
During the procedure, surgeons gain access to the heart through a six-
to eight-inch incision through the patient's side. Once the surface of
the heart is exposed, they fire short pulses of laser energy into the left
ventricle -- the heart's main pumping chamber -- while it is engorged with
blood. A computer synchronizes the laser pulses with the pumping of the
heart, and the blood in the chamber keeps the laser burst from traveling
any further.
Depending on the extent of the heart disease, the surgeons create 20 to
40 channels in the moribund heart muscle, and the holes on the heart's surface
seal themselves with clotted blood and heal over. Patients typically go
home after four days in the hospital.
"The patients are now doing things they couldn't before -- shopping,
gardening, driving and other everyday activities -- and without debilitating
pain," Lowe said. "They have also lessened the amount of heart
medications. If these benefits are sustained over time, this will be another
important therapy for a very sick group of patients."
Specifically, the procedure is approved for patients who have not responded
to the two standard therapies for blocked or diseased coronary arteries:
coronary artery bypass surgery or balloon angioplasty. In a bypass procedure,
veins from the leg are used to redirect oxygen-rich blood around blockages
and directly to heart muscle. In angioplasty, a tiny balloon is threaded
through the arteries feeding the heart and inflated, clearing plaque blocking
the artery.
"At this point, we do not know exactly why this procedure works,"
he explained. "We do know that there is new capillary growth into the
new channels. It could be that when oxygen-rich blood reaches heart muscle
starved for oxygen, growth factors are released that encourage the ingrowth
of capillaries.
"In the laboratory, we are examining why the capillaries grow into
the channels," Lowe said. "It could be that the addition of certain
growth factors could improve outcomes. Once we figure out how it works,
we can then make it work better."
Since it takes time for these new capillaries to grow, patients usually
do not begin to see major improvements until three months after the procedure,
and the improvement usually continues for nine to 12 months, Lowe said.
He added that it is too premature to consider using TMR as a routine surgical
option for patients with coronary artery disease.
"Right now, the outcomes of coronary bypass are so good, and patients
feel better right away, that I can't see the laser procedure supplanting
it," Lowe said. "But for those who have failed all other therapies,
TMR is quite promising."
In terms of cost, a typical TMR procedure ranges somewhere between those
of angioplasty and bypass surgery.