August 1, 2005 So-called vulnerable plaque is the most dangerous type of build-up in the coronary arteries. A new technique, called laser-induced fluorescence spectroscopy, uses fiber optics to determine what kind of plaque is in the arteries.
LOS ANGELES--Plaque build-up in the heart is not a good thing. But not all plaque is created equal. The most dangerous type -- called vulnerable plaque -- can lead to a heart attack. With new technology in the works, doctors may soon be able to tell their patients just what kind of plaque they have and how high risk they really are.
Medically speaking, Margaret Rogers has been around the block. "I've had two open-heart surgeries. I had a pacemaker and several angioplasties," she says. "It's been quite a trip." Her latest procedure opened an artery clogged with plaque. Each year, more than 1 million Americans die when plaque ruptures.
"If an artery to the heart abruptly closes off, that area of the heart muscle undergoes damage and the result is either a heart attack or sudden death," P.K. Shah, a cardiologist at Cedars-Sinai Medical Center in Los Angeles, tells DBIS.
Finding plaque is not hard, but Cedars-Sinai biomedical engineer Laura Marcu says it's just as important to find what's in the plaque. She says there is a need of new technology capable of detecting the inflammation.
Dr. Marcu is using fiber-optics to find out what kind of plaque a person has. The technology is called laser-induced fluorescence spectroscopy. When cells are excited by ultraviolet light, they emit a specific colored light of their own, much like a signature. Fat or lipid-filled plaque is more likely to rupture than plaque filled with less harmful collagen. With the ultra-violet light, you can see the difference.
"I think the potential is quite enormous," Dr. Shah says. And for Rogers, this new technology is just one more chance at a longer life.
Doctors say when the more dangerous type of plaque is found, there are steps patients can take to turn that plaque into the less-dangerous type, which can reduce the risk of rupture. Those treatments are currently available and used, but this technology would offer a definitive answer on just who needs those treatments.
BACKGROUND: Researchers can use a laser-based fiber-optic system to tell the difference between dangerously inflamed artery plaques from less dangerous deposits. In many cases the technique eliminates the need for an invasive biopsy. The same technique can also be used to detect brain tumors.
HOW IT WORKS: Surgeons take a fiber optic probe connected to a laser to access the desired area inside the body. The probe shines laser light on tissue, which glows (or fluoresces) in response. The way it glows tells the surgeon the chemical composition of the tissue. Inflamed artery plaque is rich in lipids, while the less dangerous variety has more collagen. Lipids and collagen fluoresce differently under laser light. The technique is called time-resolved laser-induced fluorescence spectroscopy.
WHAT ARE OPTICAL FIBERS: An optical fiber is made of ultra-thin strands of glass -- as thin as a human hair -- bundled together into cables. Optical fibers can transmit pulses of light at tremendous speeds, and are also small enough to be used as probes in a variety of medical imaging techniques. The thin glass center of the fiber where light travels is called the core. It is surrounded by a material that reflects light back into the core, called the "cladding." The cladding is covered with a plastic coating that protects the fiber from damage and moisture. The entire cable is contained in a covering called the jacket.
WHAT IS ARTERY PLAQUE: Plaque doesn't just grow on your teeth. It can also form inside your arteries -- the blood vessels that carry oxygen and blood to the heart, brain and other parts of the body. Arteries have an inner layer of muscle. When it is damaged, plaque can form, sometimes leading to a bulge in the wall of the artery. The bulges can grow big enough to cause the inner lining to rupture. The body responds by sending clotting fibers to the damaged site. Minerals, especially calcium, can become trapped in the net of fibers, and so can fats like cholesterol. The minerals and fats build up over time, causing the arteries to narrow. Blood can't flow so easily through the restricted arteries. The arteries can also become clogged, stopping blood flow completely.
The Optical Society of America contributed to the information contained in the TV portion of this report.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.