Experts Question Use of Laser Therapy for Angina -- Despite Promising Research Results
WebMD News Archive
Nov. 16, 1999 (Atlanta) -- Despite positive results from large-scale
clinical trials, use of a relatively new type of laser treatment to relieve
angina -- severe, chronic chest pain -- remains a hotly debated topic.
Two studies published in a recent issue of The New England Journal of
Medicine showcase the benefits of transmyocardial revascularization (TMR),
in which a laser is used to trigger the growth of new blood vessels in the
heart. In the same issue, however, an accompanying editorial cautioned that
without a better understanding of how TMR works, "the advisability of using
[TMR] is questionable."
Editorial co-author Richard A. Lange, MD, tells WebMD that while studies
"have shown that [TMR] is effective at relieving symptoms, what we don't
have is objective evidence that it actually improves [heart function] or an
idea of how it works." Lange is a professor at the University of Texas
Southwestern Medical Center, Dallas.
The laser procedure is used only in patients whose angina is severe and has
not responded to -- or cannot be successfully treated with -- traditional
therapies such as drugs, angioplasty (surgical artery reconstruction), or
bypass surgery. TMR is also controversial because of its risk: During clinical
trials prior to the FDA?s August 1998 approval of TMR, some patients
experienced severe arrhythmia (irregular heartbeat) -- and a small number died
within a month of undergoing the procedure. Further research, however, has
found no significant difference in one-year survival rates among patients who
received TMR and those who did not.
Researcher Keith A. Horvath, MD, a researcher involved in the first study,
defends TMR and its benefits. "There are both clinical and animal studies
... showing TMR does improve function. With echo [echocardiography, or
ultrasound heart recordings], you can see the heart wall is actually
contracting better," Horvath tells WebMD. Horvath is an assistant professor
of cardiothoracic surgery at Northwestern University Medical School in
Led by O.H. Frazier, MD, at Texas Heart Institute in Houston, Horvath's
study involved patients with severe angina who could not safely undergo either
angioplasty or coronary artery bypass. In the group that received TMR, 72% of
patients experienced significant chest pain relief and a modest improvement in
heart function. Survival rates at one year were similar for both the patients
who received TMR and those who didn?t.
Lange tells WebMD that two other studies have not produced the positive
results of the Texas study, which is why he and others remain cautious about
recommending TMR. "What you're looking for in a therapy that's going to be
effective is some consistency, and that's the thing we're lacking."
In the second reported study, researchers at 18 U.S. medical centers
followed 275 patients with class 4 (the most serious) angina. Those who
received TMR saw their angina improve and had lower hospitalization rates, but
did not have improved heart function.