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Filters Not Needed In Most Lower-Leg Interventions?
Distal embolization appears rare.
BY BRUCE JANCIN
TUCSON, ARIZ. -- Angiographically significant distal embolization during percutaneous lower extremity interventions proved to be rare and the risk of limb loss was no worse when a distal embolic protection device wasn't used, according to the findings of a large consecutive series of procedures.
This finding argues in favor of limiting use of the protective devices to selected high-risk cases, Dr. Nicholas Morrissey said at the annual meeting of the Southern Association for Vascular Surgery.
We need a national registry-- like the SVS carotid database--to enroll lots of patients and come up with risk factors.
Dr. Morrissey
Some have argued that the devices ought to be used routinely in percutaneous lower extremity arterial interventions. As yet, however, there are no scientific data to support that view. Moreover, the devices are expensive, adding at least $1,000 to the cost of a procedure. Several uncontrolled studies suggest the devices have a 5%-6% complication rate when applied in the lower extremities--far higher, as it turns out, than the rate of clinically significant embolizations without the devices, according to Dr. Morrissey of the Columbia-Weill Cornell division of vascular surgery, New York.
"We can collect ugly and potentially harmful debris with these filters. We know that. But I'd like to know, what is the clinical impact of these embolic events?" the surgeon asked.
The answer, based upon his study of 1,218 consecutive percutaneous lower extremity arterial interventions in 504 patients at New York-Presbyterian Hospital, appears to be that embolization in the large and forgiving leg arteries seldom has clinical consequences.
Just 12 angiographically significant embolization events occurred, for a 1% incidence. Angiographic patency was restored in 10 of 12 affected patients before they left the OR.
One of the two patients who left the operating room without reestablishment of preprocedural runoff eventually required amputation. That yielded a 1-year limb salvage rate of 92% in patients experiencing angiographically significant embolization, compared with a 93% rate in the other 1,206 patients in the series.
The primary patency rate at 1 year was 63% in patients without embolization but only 16% in those with embolization.
The indication for percutaneous intervention was limb salvage in 56% of cases in this series, claudication in 44%. Atherectomy was employed in 49% and angioplasty with or without stenting in 51%.
The incidence of angiographically significant embolization was 0.8% after femoral/popliteal interventions, 0.9% after tibial procedures, and 0% after iliac procedures. Nine of the 12 angiographically significant embolization events followed atherectomy, a trend that didn't reach statistical significance because of the small number of events in this series. Indeed, Dr. Morrissey was thwarted in one of his main study goals, which was to identify risk factors for significant embolization. There were simply far too few such events to draw conclusions, even in a series of more than 1,200 procedures.
"My feeling is this: We need to do these kinds of procedures and use these devices with good evidence behind it. I think we need a national registry--something like the Society for Vascular Surgery carotid database--to enroll lots of patients and come up with risk factors. I don't think an industry-sponsored randomized, controlled trial is going to be adequate; it would take too many patients, and no one's going to invest that kind of money," he said.
Discussant Scott L. Stevens said that, while an embolic shower can never be a good thing and it seems intuitively obvious that protective devices should be used in all vascular interventions, the reality is that many things can go wrong with the devices: They may fail to fully engage larger proximal lower extremity vessels, snag on a stent strut, interfere with balloon deflation, allow microemboli to pass through, and result in technical misadventures during device retrieval.
Experience has taught Dr. Stevens to use distal protection selectively. He considers it when he suspects soft thrombus because the guide wire slides effortlessly across a long-segment occlusion and symptoms suggest an acute presentation, for heavily calcified lesions, when extensive atherectomy is planned, or when there is single-vessel outflow to the foot.
"We consider protection when the stakes are high and the chances for embolic injury significant. In these situations, the time spent placing the device is usually well spent. It sure beats cancelling the rest of the day's cases to take time to dig out embolic debris after the completion angiogram," observed Dr. Stevens, a vascular surgeon at the University of Tennessee, Knoxville.
Dr. Morrissey said he and his New York colleagues don't have a rigid protocol, but they often reach for a protective device when they suspect acute thrombus, and they invariably do so prior to atherectomy of a severely calcified lesion.
"I'm not convinced calcification will turn out to be a significant indication in the absence of atherectomy, though," he added.
Dr. Morrissey indicated he has no relevant financial conflicts with commercial interests.
When asked to comment on this story, Dr. Mark D. Morasch, associate professor of surgery, Northwestern University Feinberg School of Medicine, Chicago, stated: "So much of what we do, especially in the lower extremity, lacks evidence for benefit. Clearly there is substantial cost involved either way.
"I would second Dr. Morrissey's comments regarding the benefits which could be derived from expanding the SVS-sponsored registry. With this type of information we could better guide the development of practice guidelines and quality performance measures for our members to use."
Dr. Morasch is also an associate medical editor of VASCULAR SPECIALIST.
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© 2010 VascularWeb. All rights reserved. Use of the VascularWeb site constitutes acceptance of all of the policies, rules and regulations for the site.