Historically, these procedures were done by interventional radiologists. These procedures are often done to treat hypertension, however, randomized clinical trials haven't shown that they actually do control a patient's blood pressure.
The study reviewed data from Medicare claims. In 1996 radiologists performed 4,700 renal artery interventional procedures (balloon angioplasty, stent or both), while cardiologists performed 2,380, said Timothy Murphy, MD, associate professor of radiology, Brown University Medical School, and lead author of the study. By 2000, cardiologists did 9,220 of these procedures (a 3.9-fold increase in annual volume) while radiologists increased the performance of this service to 7,660 (a 1.6-fold increase in annual volume). "It is important to note that cardiologists self-refer, and that could be one of the reasons why there is such a large increase in the number of procedures they are doing," Dr. Murphy said.
The greatest increase in the use of renal artery interventions occurred in the southeast (Alabama, Kentucky, Mississippi, North Carolina, South Carolina and Tennessee) with an increase from 22 per 100,000 Medicare beneficiaries in 1996 to 86 per 100,000 beneficiaries in 2000. The annual volume of renal artery interventions by cardiologists increased more than 15-fold in this region, Dr. Murphy said. "If this growth rate by cardiologists in the southeast region continues, at the end of 10 years, every man, woman and child in these states will have had a renal artery stent," he said.
The lowest rate of increase was in the northeast (Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, Vermont): 18 per 100,000 beneficiaries in 1996 to 26 per 100,000 beneficiaries in 2000. The regional differences "prove there is no consensus on how these patients should be treated. Somebody is wrong. Patients are either being over or under treated," Dr. Murphy said.
"Blockages in the renal arteries is common, seen in 6-18% of patients undergoing coronary arteriography and in 16-40% of those patients undergoing aortography for aneurysms or peripheral vascular disease," Dr. Murphy said. The average hospital cost for a renal artery stent is about $10,000, Dr. Murphy said. "If you look at these numbers, and you look at the mind-boggling growth in renal artery interventional procedures, you could be talking about several hundred million dollars, even up to more than a billion dollars annually to treat these patients," he said.
A multi-center clinical trial is scheduled to begin the end of this year to determine the best role for renal artery angioplasty. In the past, clinical trials have looked at its effect on hypertension, and have found little benefit, Dr. Murphy said. This trial will examine its affect on stroke, heart attack, heart failure and worsening renal function, he said. This study should help resolve the confusion regarding the need for renal artery stenting, he added.
The study appears in the September issue of the American Journal of Roentgenology.
Journal
American Journal of Roentgenology