Cath Lab Digest

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How prevalent is critical limb ischemia now?

Critical limb ischemia is, unfortunately, quite prevalent. There are about 1,000 cases of critical limb ischemia per 1 million in the U.S. population. That’s somewhere between 50,000 and 75,000 patients a year that are affected.

What are the current treatments for critical limb ischemia and why are they not always successful for patients diagnosed with it?

Standard treatment for critical limb ischemia right now involves revascularization. This can happen either via bypass surgery or via a percutaneous intervention such as angioplasty and stenting. The problem is that these patients have blockages in the arteries that feed blood to the leg and currently, treatment revolves around getting around or eliminating those blockages. That treatment is fairly successful but the problem is that rerouting the plumbing so to speak doesn’t treat the underlying disease, which is atherosclerosis. It simply reroutes blood around the blockage so one can imagine in that situation that if there’s progression of the disease, there can be redevelopment of blockage in the future and furthermore, the conduits that we use for bypass or the stents that we use when we do percutaneous treatments are not always durable. They can thrombose, clot off, and redevelop blockages within them.

Why are some patients completely ineligible for bypass surgery at all?

That’s really the Achilles heel of treating the whole disease. The fact of the matter is that when a patient comes to you with critical limb ischemia, there’s a 50% chance that that patient is not even eligible for any kind of treatment and the reasons are varied. Most commonly is that the degree of atherosclerosis is such that there is nothing that we can reconstruct. If a blockage is present in the middle of a thigh or at the knee, it’s easy for us to do a bypass around that blockage down to a healthy artery below the blockage, but in patients with very extensive disease, even very low in the foot, below the knee, into the foot, the blockages persist and there is no target blood vessel to which we can route the bypass. That’s a common reason why patients are not candidates for surgery.

Other patients, who may be a candidate for anatomic reasons are not because they have significant comorbidities, severe coronary artery disease, severe pulmonary disease that precludes putting the patient to sleep under anesthesia. Other patients are so debilitated by the time they see us with their limb ischemia that they don’t really have rehabilitation potential after you subject them to a pretty major operation such as bypass surgery.

Other patients are ineligible because right now as far as bypass surgery is concerned, the only reasonable way to do bypass surgery to the small vessels below the knee is to use the patient’s own vein. Many patients, for a variety of reasons, don’t have an available vein to harvest.

Patients come to us with disease that is so far advanced that there is no way we can save their leg and we end up having to do what is called a primary amputation.

When these treatments are unsuccessful, patients generally lose a limb. Does that often result in death also?

It does result in death. The outcome for these patients when we meet them, if they are not eligible for any treatment or revascularization, is very dismal. If you take that whole group of patients, half of them end up with an amputation within 6 months and 20% of them end up dying within 6 months and the overall 5-year mortality for critical limb ischemia is 70%, which rivals that of many cancers.

What is the study that you’re currently working on for Ohio State University that would possibly help these patients who are ineligible or for whom the treatments are unsuccessful?

One of the things that all vascular surgeons have learned over the last several decades is that some patients come in with blockages in their artery and they compensate fairly well and aren’t affected very severely. Some patients come in with blockages in their artery and are affected very severely to the point of getting gangrene of their feet or developing critical limb ischemia. The difference between those 2 groups of patients is that the group that does better is able to mount a very nice collateralization response; the body forms new channels, new pathways, new blood vessels by which blood can be routed around the blockage and still feed the tissues below the area of the blockage. That’s an autologous response, but in the folks who have very severe critical limb ischemia, that response can be impaired and what we are seeking to do is augment that natural response to the point that patients get enough collateral blood flow that we can hopefully prevent amputations for them.

How do you plan to augment that natural response?