In one of the largest studies to date, researchers have shown that transmyocardial revascularization, or TMR - a surgical procedure that uses a laser to drill holes in the heart - can reduce or alleviate angina (chest pain) in a majority of individuals for at least five years, according to research being presented at the American Heart Association's Scientific Sessions 2000.
Meanwhile, another study being presented today may open the door to a non-surgical form of the laser procedure.
TMR uses a carbon dioxide laser to make multiple channels in the heart for blood to flow through. Although no one is sure exactly why or how the procedure helps to reduce chest pain, it has proven to be effective over the short-term. Now the results of a new study indicate that TMR is also effective for longer periods of time. Researchers report that 60 percent of the patients in their study who've undergone TMR have had chest pain relief for at least five years.
"Whatever symptom relief these patients had at one year seems to be holding true out to five years," says Keith Horvath, M.D., lead researcher of the TMR study and assistant professor of cardiovascular surgery, Northwestern University Medical School, Chicago. "We have a significant number of patients who have experienced pain relief for as long as eight to nine years following their TMR surgery."
There are several theories as to why TMR is effective in curbing chest pain. It may be that the laser channels provide a new source of blood to the heart. Another theory is that TMR triggers angiogenesis -- the stimulation of new blood vessel growth. Yet another theory is that nerves in the affected area of the heart are destroyed, numbing the heart and thus relieving chest pain.
Horvath and his colleagues studied 65 patients whose average age was 63. All of them had severe chest pain that was not alleviated through other methods. Sixty-three percent had unstable angina, 75 percent had suffered at least one heart attack, 93 percent had undergone one bypass surgery, 36 percent had undergone at least one angioplasty, 67 percent had angina class IV and 33 percent had class III. The higher the angina class, the more severe the chest pain. The laser was used to create an average of 25 tiny holes in various locations of the heart muscle.
Postoperatively, 66 percent of the patients were in either class I or II and an additional 12 percent of the patients had no chest pain five years after TMR. A decrease of at least two angina classes was considered significant and by this criterion, 60 percent of the patients had successful long-term angina relief, Horvath says.
"These patients were seriously ill," he says. "They were having chest pain with only minor exertion several times a day and were taking 10 to 20 nitroglycerin tablets per week."
Meantime, a non-surgical form of TMR, which uses a different type of laser than surgical TMR, may be available to patients in about six months, according to another study being presented here. Scientists analyzed 142 patients at 17 medical centers in the United States. Half the patients received medication to control chest pain, the other half underwent percutaneous TMR (PTMR), in which a catheter is placed under the skin and is then threaded up the aorta (the heart's main blood vessel) to the inner lining of the heart wall. A holmiumYAG laser is placed on the tip of the catheter. Cardiologists use an imaging technique called fluoroscopy to get an up-close, detailed view of the heart and to help guide the laser during the procedure.
"PTMR is much simpler and less invasive than surgery," says Gregg Stone, M.D., director of cardiovascular research and education, Cardiovascular Research Foundation, Lenox Hill Hospital, New York. "It's an outpatient procedure that doesn't involve the use of general anesthesia or open heart surgery. This is a significant advance."
Stone will present the six-month safety and efficacy data at the meeting here. "Our hopes are that the patients who underwent PTMR in our study will show decreased chest pain, increased blood flow to the heart and improved exercise capacity at six months," he says.
Horvath says one major advantage of surgical TMR compared to PTMR is that the heart is exposed, allowing the laser to create channels through the full thickness of the heart rather than just the inner surface of the heart muscle. In the future, TMR may be used in combination with coronary bypass surgery to provide chest pain relief in areas with widespread blockages.
Other researchers in the TMR study are Sary F. Aranki, M.D.; Lawrence H. Cohn, M.D.; O. Howard Frazier, M.D.; Kamuran A. Kadipassoglu, Ph.D.; Steven W. Boyce, M.D.; Bruce W. Lytle, M.D.; and Allan M. Lansing, M.D.
Other researchers in the PTMR study are Ronald I. Rubinstein, M.D.; Dwayne Schmidt, M.D.; Edward Kosinski, M.D.; Gregory Mishkel, M.D.; and Paul Teirstein, M.D.