Optimisation of the non-invasive assessment of critical limb ischaemia requiring invasive treatment

Abstract

Objective: to assess the optimal cut-off values of toe blood pressure (TBP) and transcutaneous oxygen pressure (TcpO2) in the supine and sitting positions, in order to accurately detect the presence of severe leg ischaemia requiring invasive treatment. Methods: in 49 consecutive patients (65 legs) with severe ischaemia according to clinical symptoms of Fontaine III or IV and a lowered ankle blood pressure, TBP and TcpO2 were measured in the supine and sitting positions. Treatment within 6 weeks after the diagnosis was classified as either conservative or invasive (revascularisation or amputation). Results: of the 65 legs, 38 (58%) required invasive treatment. The mean ankle pressure for this group was 70 mmHg. The optimal cut-off value for TBP was 38 mmHg and for TcpO2 35 mmHg. A TBP of ≤ 30 mmHg and a TcpO2 < 25 mmHg while supine, showed likelihood ratios (LR) of 7.0 and 3.3, respectively, and when combined an LR of 12.4. Measurements in the sitting position did not enhance diagnostic power. Conclusions: the need for invasive therapy in patients with severe leg ischaemia might be predicted by measuring TBP and TcpO2, using the above-mentioned cut-off values.