Drilling a series of holes through the heart with a laser to improve blood flow to nutrient-starved heart muscle relieves chest pain and improves quality of life for patients who have run out of other options for treatment of heart disease, three studies conclude.

At the American Heart Association's annual meeting, Dr. Daniel Burkhoff of Columbia University described laser-drilling 30 tiny channels through the heart muscle of 92 patients with severe chest pain. A year later, 61 percent of the group reported their pain was half to one-third what it was before treatment, in contrast to 11 percent of patients who received only medication.

The laser-treated patients could also exercise longer and reported a better quality of life. Dr. Keith Horvath presented similar results using a different laser with patients at Northwestern University Medical School. So did Dr. Stephen Oesterle of Harvard Medical School, who drilled shorter channels from inside the heart.

Burkhoff says researchers began considering the laser procedure - called transmyocardial revascularization, or TMR - after discovering that the hearts of alligators were nourished by a system of holes in the heart muscle. How it works, however, is still a mystery.