The rationale of this study is to establish a registry to detect and follow patients with CLI treated in Vienna. The Vienna CLI registry is meant to document the incidence, prevalence, and actual outcome of CLI patients in a real world setting and should serve as a tool for the evaluation of medical, endovascular and surgical interventions. It will help determining the prognosis of individual patients and have impact on economic and political decisions in Vienna concerning this disease and the related costs.

This is a prospective observational cohort study including consecutive patients with CLI. The study will be initiated as a single center evaluation and is intended to be step-wise expanded to a Vienna-wide systematic survey. The study will include patients with chronic critical limb ischemia and ischemic ulcerations as defined by Fontaine stage IV or Rutherford stages 5 & 6. The study will include all patients presenting with CLI to the participating centers including inpatients and outpatients.

Patients will be followed up 1 month, 3 months, 6 months, 12 months and then every 6 months. The study will be continued at least until the 5 year data of the last included patient are available.

Inclusion Criteria:

• Chronic (> 2 weeks) critical limb ischemia in one or both of the lower extremities with necrosis and/or gangrene in the limb (peripheral artery disease IV according to Fontaine's classification or Rutherford stage 5 & 6) of whatever genesis (atherosclerotic, aneurysmatic, embolic, inflammatory)
• ankle/brachial index < 0.4 or toe pressure < 30 mmHg
• Ability to give written informed consent

Exclusion Criteria:

• o Ulceration exclusively due to nonvascular causes like neuropathy (without coexisting hemodynamic impairment as defined above) or venous ulceration (without coexisting arterial impairment as defined above)

tertiary care centre