Angiosome～From the Standpoint of Bypass Surgery

Distal Bypass Improves Skin Perfusion Pressure at the Whole Foot Regardless of Angiosomes in Patients with Chronic Limb-Threatening Ischemia

Objectives: Distal bypass surgery's effect on tissue blood pressure beyond a focal angiosome remains debated. This study assessed tissue blood pressure in both direct revascularized angiosome (DRA) and indirect revascularized angiosome (IRA) after bypass surgery, utilizing repeated skin perfusion pressure (SPP) measurements. Methods: Twenty-nine limbs in 27 chronic limb-threatening ischemia (CLTI) patients (22 males and five females, age: 70.2 ± 9.3 years) who received distal bypass surgery were enrolled. SPP measurements were conducted for the DRA and IRA at 10 time intervals, encompassing both preoperative and postoperative periods of every 3-5 days until 30 days. Results: In total, 486 SPP measurements were collected from 58 measurement sites, and the transition of the SPP at the DRA was 35.4-62.5-59.5-70.2-58.2-62.2-63.1-63.6-63.8-73.4 mmHg and IRA was 29.4-53.4-53.7-58.8-51.3-63.1-47.9-62.1-57.6-61.0 mmHg. No significant differences were observed between SPP at the DRA and IRA. Fifteen wounds on the DRA (63%) and five on the IRA (100%) healed. Conclusion: Distal bypass improves SPP in both direct and IRAs of CLTI patients. These data indicated distal bypass improves tissue blood flow at entire foot regardless of angiosomes.

Evaluation of Hyperspectral Imaging for Follow-Up Assessment after Revascularization in Peripheral Artery Disease

Background: Assessment of tissue oxygenation is an important aspect of detection and monitoring of patients with peripheral artery disease (PAD). Hyperspectral imaging (HSI) is a non-contact technology for assessing microcirculatory function by quantifying tissue oxygen saturation (StO₂). This study investigated whether HSI can be used to monitor skin oxygenation in patients with PAD after appropriate treatment of the lower extremities. Methods: For this purpose, 37 patients with PAD were studied by means of ankle–brachial index (ABI) and HSI before and after surgical or endovascular therapy. Thereby, the oxygenation parameter StO₂ and near infrared (NIR) perfusion index were quantified in seven angiosomes on the diseased lower leg and foot. In addition, the effects of skin temperature and physical activity on StO₂ and the NIR perfusion index and the respective inter-operator variability of these parameters were investigated in 25 healthy volunteers. Results: In all patients, the ABI significantly increased after surgical and endovascular therapy. In parallel, HSI revealed significant changes in both StO₂ and NIR perfusion index in almost all studied angiosomes depending on the performed treatment. The increase in tissue oxygenation saturation was especially pronounced after surgical treatment. Neither heat nor cold, nor physical activity, nor repeated assessments of HSI parameters by independent investigators significantly affected the results on StO₂ and the NIR perfusion index. Conclusions: Tissue oxygen saturation data obtained with HSI are robust to external confounders, such as temperature and physical activity, and do not show inter-operator variability; therefore, can be used as an additional technique to established methods, such as the ABI, to monitor peripheral perfusion in patients with PAD.

The predictive value of microperfusion assessments for the follow-up of tibial bypass grafts

OBJECTIVE

We conducted a prospective evaluation of microperfusion parameters after tibial bypass surgery was performed. Differences between grafts with occlusions during follow-up and patent grafts were analyzed in relation to the pedal arch quality.

METHODS

Patients receiving tibial bypass grafts for chronic limb-threatening ischemia from 2019 to 2020 were included. Assessment of microcirculation (parameters: hemoglobin oxygen saturation [sO₂] and flow) was done by laser Doppler flowmetry and white light spectrometry (oxygen-to-see), supine and in elevation, whereas the macrocirculation was evaluated by the ankle-brachial index and duplex ultrasound examination. The quality of run-off was graded for each patient. Measurements were performed preoperatively, 1 day postoperatively, and after 6 months. Patients with graft occlusions during follow-up (OCCLUDED) and patients without occlusions (OPEN) were compared.

RESULTS

We included 42 patients (13 women, 29 men; mean age, 76.1 years; range, 60-89 years) were included. The patency of all grafts 1 day after the operation was confirmed by ultrasound examination. The overall analysis of the microcirculation showed significant changes in both the supine and elevated leg position between measurements taken preoperatively, 1 day after the operation, and after 6 months for the parameters sO₂ and FLOW (sO₂ supine, P = .001; sO₂ elevated, P < .001; FLOW supine, P < .001; FLOW elevated, P < .001). The comparison of the values 1 day after the operation yielded significantly decreased microperfusion parameters (both O₂ and FLOW) in the group that developed bypass occlusion in the later follow-up period (sO₂ supine: OCCLUDED, 35.7% [7.3-65.0] and OPEN, 48.7% [25.0-72.3] P = .011; FLOW supine: OCCLUDED, 27.7 A.U. [12.7-52.7] and OPEN, 57.3 A.U. [16.0-106.7], P = .008). No significant differences in the severity of the arch impairment was found between the OPEN and OCCLUDED groups (P = .651). Absolute values of the parameters sO₂ and flow showed no correlation with the pedal arch classification.

CONCLUSIONS

Significantly poorer microperfusion was detected postoperatively in patients with later occurrence of graft occlusions despite patent grafts on the first postoperative day. Microperfusion measurements might be a possible tool for the prediction of graft failure.