DALLAS, April 18 -- Small hospitals that perform procedures designed to unclog heart arteries may be catching up to their larger counterparts, according to a 14-year study that shows the gap in mortality rates between high- and low-volume hospitals has gotten smaller. The study appears in today1s Circulation: Journal of the American Heart Association.
Whether angioplasty -- a common technique for opening clogged heart arteries - should be limited to hospitals that perform at least 200 procedures annually has sparked much debate in recent years.
Percutaneous transluminal coronary angioplasty (PTCA) involves threading a balloon on the tip of a catheter into an artery narrowed by fatty deposits and then inflating the balloon to open the vessel, thus increasing blood flow to the heart. Several studies have shown that complications from the procedure are fewer at institutions that perform over 200 of the procedures each year.
"This study suggests that less restrictive volume standards may be justified in less populated areas, where the alternative is no access to angioplasty," says the study1s author Vivian Ho, Ph.D., an assistant professor of economics and management at Washington University1s Olin School of Business in St. Louis, Missouri.
"This may be true for patients undergoing emergency angioplasty for the early treatment of acute heart attacks, a situation where the benefits from the procedure tend to outweigh the risks," says Thomas J. Ryan, M.D., of Boston University Medical Center, who chaired the committees that developed the first two guidelines on angioplasty as well as the recent guidelines for acute heart attack. Ryan points out that the gap that still exists between low-volume and high-volume hospitals is significant. "It appears that the recommendation for elective angioplasty will continue to emphasize procedural volume minimums at the 400 to 600 procedures per year level," he says.
The American Heart Association and the American College of Cardiology have issued joint guidelines that suggest that elective angioplasty be limited to hospitals that perform at least 200 of the procedures annually. The two organizations were the first to identify the importance of institutional volumes as a determinant of angioplasty outcomes in guidelines that were initially developed in 1988 and updated in 1993. The minimum number of 200 procedures per institution annually was derived at by consensus opinion of experts, Ryan says.
Ryan says more recent studies offer evidence that the minimum volume recommendation for each hospital should actually be around 400 to 600 procedures per year. This figure will likely be advised in the new PTCA guidelines currently being developed, he says.
However, Ho says, "We have to consider that these low-volume facilities can improve over time, and allowing smaller hospitals to perform angioplasty will give more patients access to this lifesaving procedure."
Ho looked at the outcomes of 353,488 angioplasty patients who were treated in California hospitals between 1984 and 1996. "Over time, the difference in mortality between the high-volume and low-volume hospitals narrowed significantly," she says.
In her study, Ho looked at the mortality rates for patients admitted to hospitals to undergo angioplasty, and also those who required bypass surgery because their blockages were too severe for angioplasty. The patients1 average age was 63 years; 31 percent were women; 22 percent treated with angioplasty had suffered a heart attack, and roughly 11 percent of the angioplasty patients had more than one blocked artery.
The study was also divided into three time spans: 1984 to 1987, 1988 to 1992 and 1993 to 1996. During 1984 to 1987, the angioplasty mortality rate for hospitals performing fewer than 200 procedures a year (low volume) was 2.5 percent compared to 1.3 percent for hospitals doing more than 400 angioplasties a year (high volume). Between 1993 and 1996, the rate dropped to 1.7 percent for low-volume hospitals compared to 1.3 percent for the high-volume institutions.
The number of angioplasties being performed in California increased steadily during the years of the study. The median annual angioplasty volume for 1984 to 1987 was 89 procedures. The median annual volume rose to 200 during the years 1988 to 1992 and rose again to 272 during 1993 to 1996.
"The relative benefit for patients treated in high-volume hospitals needs to be put into perspective with regard to minimum-volume standards," Ho says. "For instance, a lack of ready access to the procedure could have adverse health consequences for people living in less populated areas who require emergency angioplasty. So, we have to consider the possibility that these low-volume hospitals can improve over time."