A pilot study suggests that the results of minimally invasive angioplasty and stenting to restore blood flow to the kidneys can be significantly improved if a suction device is used to remove the material blocking the vessel. The results, from a study at Wake Forest University Baptist Medical Center, are reported in the July issue of the Journal of Vascular Surgery.
"Three to six weeks after the minimally invasive procedure, kidney function was roughly equal to what is typically achieved with major surgery," said Matthew S. Edwards, M.D., M.S., assistant professor of surgery and lead author. "We hope this will lead to a better way to do angioplasty and stenting by preventing damage to the kidneys and improving kidney function."
The study suggests that the key to success was using suction to prevent the plaque and other material that make up blockages from reaching the kidneys and causing damage. In previous studies of angioplasty without a suction or filtering device, results have been inconsistent.
Angioplasty involves inserting a balloon-like device into the vessel to crush fatty deposits that are blocking blood flow. In many cases, a stent, or scaffold-like device, is inserted to help keep the vessel open. In this study, Edwards used what is called a "distal embolic protection system" that consisted of a balloon system to temporarily block the vessel and a suction system to remove the bits of crushed material that made up the blockage. (Undesirable particles and air bubbles in the blood are known generally as "emboli.")
The study involved 32 patients with a mean age of 70 years. Kidney function improved in 50 percent of the procedures and worsened in none. The narrowed arteries were reopened in 100 percent of cases and mean blood pressure was reduced from 176/81 mm Hg to 158/76 mm Hg.
"These data suggest that distal embolic protection systems may prevent damage to the kidneys during angioplasty and stenting and warrant further investigation," said Edwards.
Surgery to restore blood flow to the kidneys is a common procedure, said Edwards. Previous research at Wake Forest found that about 7 percent of healthy older Americans have renal artery stenosis, or narrowing in the main artery leading to the kidneys, and about 40,000 of the 3.5 million Americans who have the condition will require surgery.
The condition is most common in people with severe, difficult to control high blood pressure. Over time, the hypertension can lead to the narrowed vessels. Conversely, in a small number of cases, it is narrowed vessels to the kidneys that cause hypertension. Surgery may be called for when patients have abnormal kidney function because of reduced blood flow to the organs, or when the uncontrolled hypertension has led to heart failure or blockages in other vessels in the body, such as those leading to the heart.
Without successful surgery to open the kidney vessels and improve organ function, patients have a much greater risk of adverse cardiovascular events, dialysis dependence and death, Edwards said. He plans further studies, in larger groups of patients, of the less invasive procedure for restoring blood flow.
Edwards presented the results at the 2006 annual meeting of the Southern Association for Vascular Surgery. He has received funding for additional research: $540,000 from the National Institutes of Health's National Heart, Lung and Blood Institute; $375,000 from the American Vascular Association/Lifetime Foundation's Mentored Clinical Science Award, and $385,000 unrestricted research grant from the medical technology company, Medtronic AVE.
Co-researchers were Brandon L. Craven, B.S., Jeanette Stafford, M.S., Timothy E. Craven, M.S.P.H., Kenneth J. Sauve, B.S., Juan Ayerdi, M.D., Randolph L. Geary, M.D., and Kimberley J. Hansen, M.D.
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