"For the first time, doctors have shown that by inserting extra genes into the heart, they can enable patients to grow their own bypasses.
The approach could someday spare patients the need for bypass surgery, in which a piece of blood vessel is grafted into place to create a detour around a blockage.
Experts say this new gene-insertion procedure, tested initially in the legs and now in the heart, represents the first example of gene therapy actually correcting a human ill.
Several competing teams of doctors have injected a gene that makes a protein called vascular endothelial factor - or VEG-F - into the hearts of people who have clogged vessels but are too sick to undergo ordinary bypass surgery or angioplasty. Ordinarily, the gene only does its work during fetal development in the womb.
The doctors found clear, and in some cases dramatic, evidence that the gene prompts the heart to sprout tiny new blood vessels to nourish blood-starved muscle and relieve crippling chest pain.
Nevertheless, the procedure is still highly experimental and is probably several years away from routine use.
"We are trying to take damaged adult organs and return them to youth," said Dr. Ronald G. Crystal of Cornell Medical School in New York City. He and others reported their findings yesterday at a meeting of theAmerican Heart Association in Dallas.
Still unclear is whether this kind of genetic manipulation will work any better than a more direct medical approach - giving people doses of the protein made by the gene. At a conference last March, doctors from the University of Minnesota showed that the VEG-F protein appeared to ease angina in 13 of 15 patients treated.
Among those receiving injections of the VEG-F gene were 16 patients of Dr. Jeffrey Isner of St. Elizabeth's Medical Center in Boston, all of them heart attack victims who suffered excruciating chest pain at even the mildest exertion.
Some of Isner's patients were taking as many as 60 nitroglycerin tablets a week for their pain. Now all have improved substantially, and the average dose is 21/2 pills weekly. Of the 11 patients who have been followed up for at least three months, six are free of pain.