As with the other stages of peripheral artery disease (PAD), treatment of the most severe stage — critical limb ischemia — should be multifaceted and include medication and lifestyle modifications, as described in this issue's lead article. But with critical limb ischemia (CLI), clinicians can't wait to observe the effectiveness of that approach. "If these patients are not effectively revascularized, they are at severe risk for loss of limb," says cardiovascular specialist Yerem Yeghiazarians, M.D.
CLI occurs when people develop severe blockages, usually at more than one location in the leg, undermining the ability of collateral arteries to at least partly accommodate the blocked flow. The clinical result is an ankle-brachial index that drops below the point where blood flow can facilitate basic activity.
"Tissue functions are impaired and there is pain, even at rest," says Michael S. Conte, M.D., chief of Vascular and Endovascular Surgery at UCSF Medical Center. Wounds that fail to heal and the development of irreversible tissue damage (gangrene) are also cardinal signs of CLI.
Choosing the appropriate revascularization technique remains a difficult challenge because, while there are multiple options, there are no established guidelines. A multidisciplinary approach — with clinicians who possess both experience with and access to the full range of revascularization options — provides the best results, says Conte, who serves on a Society for Vascular Surgery panel that is creating guidelines for evaluating new devices.
Percutaneous therapies are less invasive than open surgery, and depending on the types of blockages, physicians often consider such therapies first, especially because recent advances have expanded the available options. "At UCSF, we offer many types of percutaneous therapies, such as balloon angioplasty, cryoplasty and stenting," says Yeghiazarians. "Drug-eluting stents are also a possibility, but there is not much evidence on these yet for arteries in the legs."
When the artery is completely occluded, the team may also consider atherectomy with either lasers or devices that "shave" the plaque. "These are not yet proven as stand-alone options because they tend to be limited by recurrence," says Conte. "But as part of the armamentarium, they can offer some short-term improvement, especially when used in combination with open surgery."
In many cases — especially those who have severe disease or for whom less invasive solutions have failed — a well-done surgical bypass is the best option to preserve the limb for the long term. "Over the last 20 years, we have refined these techniques dramatically," says Conte. "So while we always carefully consider the less invasive option, when we have excellent surgery available, we don't dodge around it."
The best alternative at this point is using the patient's own vein because artificial grafts typically do not function well under low-flow conditions. Conte adds that — as with any complicated surgery — volume, surgeon experience and technical factors strongly influence the success rate. And due to the global nature of their cardiovascular disease, getting these patients safely through leg bypass surgery requires careful attention by a team of surgeons, anesthesiologists, cardiologists and nurses.
Finally, because PAD is a chronic disease, ongoing surveillance is essential. "We follow patients closely following either surgery or angioplasty, and use ultrasound to look directly at the graft or stent," says Conte. "This often enables us to see things before the patient even recognizes new symptoms."
"Part of the follow-up needs to be therapy for all cardiovascular risk factors," says Yeghiazarians.
Researchers worldwide are actively developing and testing new PAD treatments, including angiogenesis, tissue-engineered grafts, and various gene and cell therapies. "These are areas of promise, but they are not yet ready for prime time," says Michael S. Conte, M.D., who was lead investigator of the PREVENT III clinical trial, a multicenter, phase III study of an oligonucleotide therapy for the prevention of peripheral vein graft failure.
At UCSF, research efforts include drug-eluting stents, new drugs to reduce scarring in arteries and veins, gene therapy, and stem cells that may help regrow blood vessels in the leg. "In some of these areas, we are or will be doing some small-scale clinical trials for patients who have exhausted standard options," says Conte.
To contact Michael S. Conte, M.D., call (415) 353-4366.
To contact Yerem Yeghiazarians, M.D., call (415) 353-3815.
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