Fluorescence angiography compared to toe blood pressure in the evaluation of severe limb ischemia

Summary: Background: Severity of limb ischemia in peripheral arterial disease (PAD) patients is usually evaluated by clinical assessment and toe blood pressure (TBP) or transcutaneous oxygen pressures (TcPO 2). Indocyanin green angiography (IGA) is a promising tool generating a foot cartography of skin microvascular perfusion. However, there is no consensus about the fluorescence parameters that should be used to evaluate ischemia. The purpose of this cross-sectional evaluation and 3-month clinical follow-up was to determine the best fluorescence parameter for the evaluation of severe PAD, using TBP as reference. Patients and methods: IGA was realized in patients with clinical suspicion of CLI in addition to TBP and TcPO 2. Parameters from the time intensity fluorescence curve measured on the foot were compared with TBP (primary reference), and with TcPO2. Clinical outcomes (amputation, revascularization, death) were recorded at 3 months follow-up. Results: Thirty-four patients were included and IGA could be analysed in 29 of them. When all limbs were studied, no significant correlation was found between any of the measured fluorescence parameters (saturation time, ingress slope, amplitude, delay) and TBP pressure neither TCPO2. In the limbs with CLI, a significant correlation between the TBP and amplitude on the forefoot was found. According to the outcome, none of the fluorescence parameters showed a significant prognostic value in contrast to the significant results for TBP and TcPO2. Conclusions: In this study, quantitative analysis of IGA parameters did not show any prognostic value, nor was there any significant statistical association with well-established prognostic parameters such as TBP and TcPO 2 in patients with suspected CLI. A correlation was found between amplitude and TBP in patients with CLI. Topographical information such as perfusion heterogeneity was not evaluated and remains a valuable target to be investigated.

Toe brachial index measured by automated device compared to duplex ultrasonography for detecting peripheral arterial disease in older people

Introduction To investigate the diagnostic accuracy of an automated toe blood pressure device for detecting peripheral arterial disease in older people. Methods Ninety participants underwent toe and brachial blood pressure measurements and colour duplex ultrasonography of the right lower limb. Peripheral arterial disease was diagnosed if > 50% arterial obstruction was identified in any lower limb vessel using colour duplex ultrasonography. A receiver operating characteristic curve was analysed and the sensitivity and specificity of commonly used toe brachial index and toe blood pressure values were determined. Results The optimum toe brachial index threshold value for diagnosing peripheral arterial disease was 0.72 (sensitivity 76.2%, specificity 75%). The area under the curve was 0.829 (95% CI 0.743 to 0.915, p < 0.0001) suggesting fair diagnostic accuracy. A toe blood pressure of 70 mmHg was found to have excellent specificity (97.92%) for detecting PAD but poor sensitivity (42.86%). Conclusions The accuracy of automated toe blood pressure and TBI measurements was determined to be good when using colour duplex ultrasound as the reference standard for the non-invasive diagnosis of peripheral arterial disease. Results should be interpreted in the context of all clinical signs and symptoms.

Why Critical Limb Ischemia Criteria are Not Applicable to Diabetic Foot and What the Consequences are

Neuropathy, peripheral arterial occlusive disease and microvascular disturbances are important factors contributing to foot problems in diabetic patients. In the diabetic foot with ischemia, the alterations in skin microvascular function are pronounced including severely reduced capillary circulation and abolished hyperaemic responses. These microvascular disturbances, which are superimposed on the already existing structural diabetic microangiopathy, are compatible with a state of “chronic capillary ischemia” and an increased shunting of blood through arteriovenous channels. This maldistribution of blood in skin microcirculation is not detected by measurement of peripheral blood pressure (systolic ankle blood pressure, systolic toe blood pressure). As indicated in several studies toe blood pressure is a poor predictor of local tissue perfusion, tissue survival and healing of chronic foot ulcers. Consequently, the disturbances in peripheral tissue perfusion of the diabetic foot may be underestimated leading to delayed vascular interventions and/or medical treatment. Thus, measurements of peripheral blood pressure, e.g. toe blood pressure, should be combined with investigations of local tissue perfusion in order to get an adequate estimation of peripheral tissue perfusion in diabetic patients. For this purpose local skin microcirculation can be investigated by transcutaneous oxygen tension of the forefoot. Also, due to these reasons, the threshold for revascularization should be lower in diabetic patients with foot ulcer.