A New 'cool' Laser That Zaps Clogged Arteries Could Make Coronary Bypasses Obsolete
Doctors call it arteriosclerosis, a condition in which fatty deposits build up in the arteries. This blockage chokes the flow of blood supplying oxygen and nutrients to body tissues. Ultimately it may cause a heart attack or stroke. Today the standard medical response to arteriosclerosis is a variety of bypass operations that surgically detour the blood flow around the blockage. Each year more than 170,000 Americans undergo this form of major surgery. Normally the hospitalization and the convalescence following a bypass operation last four to eight weeks.
But now, if a new procedure advanced at the Cedars-Sinai Medical Center in Los Angeles proves successful, the trauma of heart bypass surgery could be eliminated for many patients. This pioneering technique is termed excimer laser angioplasty (or laser blood-vessel reshaping). It combines the wondrous powers of an advanced "cool" laser, called the excimer (developed by NASA and the Jet Propulsion Laboratory of Pasadena, Calif.), with a fiber-optic delivery system developed by electrical engineer Tsvi Goldenberg. The technique employs a laser catheter to open blocked arteries much as a plumber's snake unclogs a drain (see diagram), although with a precision that no plumber ever dreamed of.
The Cedars-Sinai team is made up of Drs. James Forrester, 47, assistant director of cardiology at the hospital, Warren Grundfest, 32, chief resident of general surgery, and cardiologist Frank Litvack, 29. They have tested the procedure successfully on human tissue obtained from cadavers. Testing on live human patients must await Food and Drug Administration approval, which the doctors hope will come within 12 to 24 months. The CSMC team met with reporter Suzanne Stevens to explain how laser angioplasty might one day revolutionize the treatment of cardiovascular disease.
How would your new procedure work?
Litvack: A laser catheter would be inserted through a skin incision in the arm or groin and advanced up the artery to the blockage. Then the laser is turned on and the blockage vaporized.
Grundfest: By vaporize, we mean that the laser could disintegrate the fatty deposits to allow a return of the blood flow into the artery.
Do you use fiber optics to guide the catheter to the obstruction?
Litvack: Yes, the catheter contains a bundle of fiber optics, some carrying laser energy, and others providing illumination. Most of the fibers in this bundle of glass strands are used to carry an image from inside the artery to a television camera that, in turn, will put a picture on a monitor. The surgeon will actually have visual contact in aiming the laser at the obstruction.
Aren't there risks in using medical lasers?
Forrester: Very serious problems. One is that medical lasers currently in use work by heat. This means they can burn a hole in the blood vessel very quickly. But we are working with a new type, the excimer laser, which operates at a lower temperature level. Furthermore, with the fiber-optic system, we think we will be able to control the laser with exquisite microscopic precision. Before these developments, using a laser on the inside of a blood vessel was a little like throwing a bomb inside a patient.
How does the excimer laser differ from other lasers?
Grundfest: A conventional medical laser can be pulsed up to a thousandth of a second. Excimer lasers can operate in billionths of a second—10 to 200 billionths of a second.
Litvack: For example, an excimer laser beam can remove the phosphorus coating on a match head without igniting it. Its ability to do this without generating enough heat to light the match makes us believe the excimer is preferable to older medical lasers.
Will laser angioplasty be 100 percent effective?
Forrester: Well, you can't get a doctor to say anything is infallible, but I think it could revolutionize the treatment of cardiovascular disease. It is potentially simpler than coronary bypass surgery; it attacks the problem right at the point of obstruction and removes it.
Could this procedure reduce the operation to an overnight hospital stay?
Grundfest: That's a reasonable speculation. I think it would be more accurate to suggest a fairly short hospitalization, maybe two to three days.
Once the laser unblocks the artery, will it stay that way?
Forrester: At this point we have no idea what the recurrence rate might be. It is likely that in some patients there could be a recurrence, but if that happens the patient presumably can be treated effectively through laser angioplasty a second time.
How much will the treatment cost?
Litvack: The equipment will be expensive; a prototype device will be in the range of $100,000. But once the equipment is averaged out over many patients, the cost per patient should not be more than $10,000, including hospitalization. This compares to up to $40,000 for a standard coronary bypass.
What caused you to turn to the excimer laser in your research?
Forrester: There is a need for improved therapy in coronary disease, and we realized this technology could be applied to the problem.
Grundfest: NASA and the computer industry are using these lasers for things like communications, sensing devices and for making semiconductor chips. The laser that we're using at the Jet Propulsion Laboratory is of greater sophistication than anything commercially available outside the engineering and scientific communities.
Can the excimer be used for other medical purposes?
Grundfest: Yes, orthopedic surgery is one possible application. You can go into the joints of the knees, the elbow, the shoulder. So far as we know, it's the only laser that cuts bone effectively without burning the bone to a cinder.
Litvack: If we prove that we have a laser that cuts tissue with incredible precision, it could be applied to brain surgery. We will be starting some experiments with neurosurgeons shortly.
When can we expect the excimer laser to make its debut in operating rooms?
Litvack: It's not going to be tomorrow but probably a year or more before a working device is available. Machines have to be built and tested, and then clinical trials can begin.
Grundfest: To date most of our research has been done, not on animals, but on human cadavers—blocked blood vessels from people who have died or vessels removed in coronary bypass surgery. The experience we've gained on human tissues makes us feel very confident that we will be able to proceed with living patients.
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