Study Explains Why Diabetics Face High Risk From Angioplasty
March 5, 2001 -- It is well known that patients with diabetes who undergo a common procedure for opening clogged heart vessels are more likely to die after the procedure than nondiabetics. But why?
Now, a new study appears to provide the answer. Researchers have found that when patients with diabetes undergo balloon angioplasty -- a procedure in which a deflated balloon is inserted into a clogged heart artery, then inflated to unclog the area -- the vessels are much more likely to clog again in diabetic patients than they would in nondiabetic patients.
This clogging phenomenon is known as "restenosis." In particular, it appears that diabetics are at risk for an especially severe form of restenosis known as "occlusion," in which the vessel almost completely closes, according to Eric Van Belle, MD, PhD, of the University of Lille, in France.
Targeting occlusive restenosis in diabetic patients is likely to save lives. "Our study provides an explanation for the previous observation of the poor outcome of diabetic patients after coronary balloon angioplasty, and suggests a new therapeutic target to improve the outcome of these patients," Van Belle tells WebMD.
Specifically, he suggests that diabetic patients who undergo the procedure might benefit from the use of a stent, a tube that can be implanted in the artery during angioplasty to keep the artery open. In addition, drugs that prevent blood clotting, specifically the ones called antiplatelet agents, may help prevent restenosis, he says.
Because the stent remains in the vessel, it can prevent it from clogging long after the procedure is completed. "Based on available data, the use of stents ... should drop the risk of occlusive restenosis in diabetics patients from the 15% range to about 5%," Van Belle tells WebMD.
In the study, over 500 patients with diabetes who underwent angioplasty were followed for an average of six-and-half years. During this period, exactly half of the patients experienced partial blockage. Another 18% experienced almost complete blockage, according to the report.
Of those patients who experienced almost complete blockage, 59% later died. But even among the group whose artery was not completely closed, about a third later died, according to the report.
Why exactly the heart vessels in diabetic patients are more likely to clog is not clear. It may be related to something that happens to the cells of the heart vessel itself, or to more generalized factors -- or to both, Van Belle says.
"An answer to these questions may help to design new pharmacological approaches that hopefully should improve the outcome of this high risk group of patients," Van Belle tells WebMD.
In an editorial accompanying the report, Burton E. Sobel, MD, suggests that high levels of insulin in the blood of diabetics may affect clotting or the cells in the smooth wall of blood vessels that are involved in the clogging. In nondiabetics, the smooth muscle cells tend to grow back, while in diabetics a lot of excess material accumulates that can cause ruptures, he suggests.