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.