"Angioplasty cracks open the vessel wall and does a fair amount of damage," said Dr. John Cooke, associate professor of cardiovascular medicine at Stanford University Medical Center.
The scarring from the procedure apparently formed a 90 percent obstruction in one of the blood vessels leading from Cheney's heart -- the same artery that was forced open by angioplasty in November following Cheney's fourth heart attack. Doctors performed another angioplasty on Cheney yesterday, to clear the blockage again.
The renarrowing of a vessel due to scarring from angioplasty is called restenosis. Unlike heart disease, it is not something that patients can remedy by changing their diet or getting more exercise.
"The question patients always ask is: 'Is there something I can do related to risk factor modification?' " Brindis said. "The answer is: not really. The process of renarrowing is basically a biologic, scar-tissue phenomenon."
Still, doctors say significant progress has been made in cutting down restenosis. And some new approaches are promising even better results.
Cheney was the beneficiary of one advance -- the use of stents to keep blood vessels propped open following angioplasty. Used routinely for the past decade, the tiny mesh tubes have cut the rate of restenosis by about half, Brindis said.
More promising are two approaches familiar to oncologists fighting cancer.
One is radiation. Brindis said two companies recently won approval from the Food and Drug Administration for techniques that use small amounts of radioactive substances to prevent cells in the blood vessel from growing abnormally.