Percutaneous Intervention of Chronic Total Occlusion in Critical Limb Ischemia

Chronic critical limb ischemia (CLI) represents the extreme spectrum of peripheral arterial disease (PAD), accounting for about 1% to 3% of all PAD patients. CLI manifests as ischemic rest pain, gangrene and/or ulceration. CLI is considered chronic when symptoms persist for more than 2 weeks. It occurs when skin perfusion pressure at the affected site is reduced to a degree such that tissues’ resting metabolic needs are not met. Generally, ischemic rest pain occurs when systolic pressures at the ankle and toe are lower than 50 mm Hg and 30 mm Hg, respectively. Particularly in non-diabetic patients, the loss of perfusion pressure is due to multi-level occlusions between the aorta and pedal vessels. Some ulcers are caused solely by ischemia; others are caused by a combination of factors such as ischemia, neuropathy, trauma and venous insufficiency. Regardless of the etiology of the ulcer, if ischemia is present, it must be corrected to achieve wound healing. The majority of the foot ulcers present below the ankle are typically due to arterial insufficiency. Wound healing is an inflammatory response and, therefore, requires greater blood flow than is needed to simply sustain tissues. Perfusion pressure needs to be about 70 mm Hg at the ankle and 50 mm Hg at the toe to achieve wound healing. Collateral flow generally lacks enough pressure-head to achieve wound healing. To heal wounds in chronic CLI, therefore, it becomes necessary to establish straightline pulsatile flow from the aorta to the vessel supplying the affected area. Like ischemic ulcers, ischemic gangrene results from spontaneous necrosis of the skin due to severe ischemia, usually precipitated by some local trauma. While the underlying cause of gangrene is ischemia, the treatment often is primary amputation of the affected part. A study that involved a large Medicare database found the rate of primary amputation for gangrene to be 67%. The same study reported surgical revascularization before amputation at 23% and percutaneous revascularization at 10%. The study also reported underutilization of vascular studies, such as ABI and angiography, to diagnose ischemia before amputation. Failing to correct underlying ischemia before primary amputation often results in amputation revision to higher levels, until the plane of adequate vasculature is reached. Major amputations such as LLC , TM