Critical limb ischemia limb threat chronic limb threatening ischemia clti also known as critical limb ischemia cli is an advanced stage of peripheral artery disease pad it is defined as ischemic rest pain arterial insufficiency ulcers and gangrene . Critical limb ischemia cli is a severe blockage in the arteries of the lower extremities which markedly reduces blood flow it is a serious form of peripheral arterial disease or pad but less common than claudicationpad is caused by atherosclerosis the hardening and narrowing of the arteries over time due to the buildup of fatty deposits called plaque. Critical limb ischemia cli critical limb ischemia cli is a severe obstruction of the arteries which markedly reduces blood flow to the extremities hands feet and legs and has progressed to the point of severe pain and even skin ulcers or sores the pain caused by cli can wake up an individual at night. Critical limb ischemia is defined as limb pain that occurs at rest or impending limb loss that is caused by severe compromise of blood flow to the affected extremity 1 hirsch at