Making angioplasty safer

Dec 2 2005

When life-threatening problems occur during angioplasty procedures, doctors may perform emergency coronary artery bypass graft surgery, but data from the Mayo Clinic indicates that need to send patients to emergency surgery has dropped sharply, according to a new study in the Dec. 6, 2005, issue of the Journal of the American College of Cardiology.

"Our review of almost 25 years of data on angioplasty suggests that there has been a dramatic reduction of almost 90 percent in the incidence of coronary artery bypass graft surgery following angioplasty; and this is despite the fact that more recently we are performing angioplasty on very high risk patients," said Mandeep Singh, M.D., F.A.C.C., from the Mayo College of Medicine in Rochester, Minnesota.

The researchers, including lead author Eric H. Yang, M.D., reviewed a unique registry of every angioplasty performed at the Mayo Clinic. The registry includes more than 23,000 cases and extends back to the first angioplasty procedure in 1979. Coronary angioplasty involves threading a catheter through blood vessels in order to re-open arteries that nourish the heart muscle, usually after a heart attack or severe chest pain. The procedure is an alternative to bypass surgery in which blood vessels taken from elsewhere in the body are used to re-route blood around a coronary artery blockage. It is also known as percutaneous coronary intervention or PCI.

Data from the Mayo registry were divided into three groups: the "pre-stent" era, 1979 to 1994 (8,905 patients); the "initial stent era," 1995 to 1999 (7,605 patients); and the "current stent era," 2000 to 2003 (6,577 patients).

"We knew there had been a reduction, but the magnitude of the reduction was a surprise to us," Dr. Singh said. "The bypass surgery rates, which were close to 3 percent, came down to 0.3 percent in the most recent time period."

Dr. Singh said the fact that angioplasty is being offered to sicker patients now makes the reduction even more remarkable. Patients requiring emergency surgery in the most recent study period had a higher prevalence of high blood pressure and heart failure, and they were more likely to have undergone previous procedures, compared to patients in the earlier study periods.

Dr. Singh said he believes stents may be responsible for much of the reduction in the rate of life-threatening problems during angioplasty procedures. Stents are tiny wire-mesh scaffolds that are inserted into the area of a coronary artery narrowing that has been opened up by a balloon or cutting device. He also pointed to other improvements in drug therapy and device technology that have made angioplasty safer and more successful.

However, among patients who did suffer serious problems during angioplasty and had to be sent into emergency surgery, the researchers did not see an improvement in survival. Death rates were statistically similar in all three study periods, ranging between 10 percent and 14 percent. Dr. Singh pointed out that there were only 41 deaths among patients who underwent emergency bypass surgery, including just two during the 2000 to 2003 study period. He said such small numbers make it difficult to calculate useful statistical comparisons.

The study authors pointed out that this analysis is based on a retrospective review of registry data from the Mayo Clinic only, not a prospective trial at multiple institutions, although Dr. Singh noted that the registry is very large.

In an editorial in the journal, John A. Bittl, M.D., F.A.C.C., from the Ocala Heart Institute, Munroe Regional Medical Center in Ocala, Florida, said that while the sharp decline in emergency bypass surgery on angioplasty patients is welcome news, he is concerned the results may be used by some providers to argue that back-up surgical facilities are no longer needed.

"Almost every hospital wants a share of the lucrative coronary intervention market and every physician hopes that in-laboratory deaths and the need for emergency bypass and will go away completely, but this ideal situation has not been attained," Dr. Bittl said.

"The assessment of elective PCI without on-site bypass surgery underway in some states is a step in the right direction. But, choosing the right metrics is challenging. The only meaningful comparison between hospitals with and without on-site surgery is the rate of death or urgent transfer to another facility within a pre-specified period of time after PCI. One proposal that mixes acute events with late endpoints like repeat revascularizations is manipulative and misleading," he added.

Dr. Bittl wrote that this study has established an important benchmark and should stimulate exploration of ways to improve angioplasty and make it even safer.