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Purpose Hyperspectral imaging (HSI) and thermal imaging allow contact-free tissue perfusion measurements and may help determine the effect of endovascular treatment (EVT) in patients with peripheral arterial disease. This study aimed to detect changes in perfusion with HSI and thermal imaging peri-procedurally and determine whether these changes can identify limbs that show clinical improvement after 6 weeks. Methods Patients with Rutherford class 2–6 scheduled for EVT were included prospectively. Hyperspectral imaging and thermal imaging were performed directly before and after EVT. Images were taken from the lateral side of the calves and plantar side of the feet. Concentrations of (de)oxyhemoglobin, oxygen saturation, and skin temperature were recorded. Angiographic results were determined on completion angiogram. Clinical improvement 6 weeks after EVT was defined as a decrease ≥ one Rutherford class. Peri-procedural changes in perfusion parameters were compared between limbs with and without good angiographic results or clinical improvement. To identify limbs with clinical improvement, receiver operating characteristic (ROC) curves were used to determine cutoff values for change in HSI. Results Included were 23 patients with 29 treated limbs. Change in HSI values and temperature was not significantly different between limbs with good and poor angiographic results. Change in peri-procedural deoxyhemoglobin, determined by HSI, at the calves and feet was significantly different between limbs with and without clinical improvement at 6 week follow-up (p=0.027 and p=0.017, respectively). The ROC curve for change in deoxyhemoglobin at the calves showed a cutoff value of ≤1.0, and ≤−0.5 at the feet, which were discriminative for clinical improvement (sensitivity 77%; specificity 75% and sensitivity 62%; specificity 88%, respectively). Conclusions HSI can detect changes in perfusion at the calves after EVT in patients with Rutherford class 2–6. Peri-procedural deoxyhemoglobin changes at the calves and feet are significantly different between limbs with and without clinical improvement. Decrease in deoxyhemoglobin directly after EVT may identify limbs that show clinical improvement 6 weeks after EVT.

Introduction: For patients with peripheral arterial disease (PAD), the various components of telemedicine, such as telemonitoring, telecoaching, and teleconsultation, could be valuable in daily management. The objective of this review was to give an overview of the current use of telemedicine interventions in PAD. Areas covered: A literature search was performed for studies that evaluated patients with PAD of the aorto-pedal trajectory, who were monitored by telemedicine and acted upon accordingly. The primary outcome was health-related outcomes. The studies that were found focused mainly on wearable activity monitoring and telecoaching in PAD (n = 4) or wound monitoring after vascular surgery (n = 2). Main results indicate that telemedicine interventions are able to detect (post-operative) complications early, improve functional capacity and claudication onset time, and improve PAD patients’ quality of life. Expert opinion: The use of telemedicine in PAD patients is still an under-explored area. Studies investigating the use of telemedicine in PAD are very limited and show varying results. Owing to its high potential in improving physical ability, lifestyle coaching, and timely detection of deterioration, future research should focus on proper implementation of telemedicine in PAD patients, including clinical and feasibility outcomes, effect on workload of nurses, and cost-efficiency.

Introduction: Peripheral arterial disease (PAD) may cause symptoms due to impaired tissue perfusion of the lower extremity. So far, assessment of PAD is mainly performed by determination of stenosis or occlusion in the large arteries and does not focus on microcirculation. Several diagnostic techniques have been recently introduced that may enable tissue perfusion measurements in the lower limb; however, most have not yet been implemented in clinical daily practice. This systematic review provides an overview of these diagnostic techniques and their ability to accurately detect PAD by peripheral tissue perfusion. Areas covered: A literature search was performed for articles that described a diagnostic technique to determine tissue perfusion in patients with known PAD compared with healthy controls. Expert opinion: So far, transcutaneous oxygen measurements are most often used to measure tissue oxygenation in PAD patients, but evidence seems too low to define this technique as a gold standard, and implementing this technique for home monitoring is difficult. New potentially suitable diagnostic tests should be non-invasive, contact-free, and quick. Further research is needed for all of these techniques before broad implementation in clinical use is justified, in hospital, and for home monitoring.

Objective Many techniques have been introduced to enable quantification of tissue perfusion in patients with peripheral arterial disease (PAD). Currently, none of these techniques is widely used to analyse real time tissue perfusion changes during endovascular or surgical revascularisation procedures. The aim of this systematic review was to provide an up to date overview of the peri-procedural applicability of currently available techniques, diagnostic accuracy of assessing tissue perfusion and the relationship with clinical outcomes. Data Sources MEDLINE, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials. Review Methods This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) guidelines. Four electronic databases were searched up to 31 12 2020 for eligible articles: MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials. Eligible articles describing a perfusion measurement technique, used in a peri-procedural setting before and within 24 hours after the revascularisation procedure, with the aim of determining the effect of intervention in patients with PAD, were assessed for inclusion. The QUADAS-2 tool was used to assess the risk of bias and applicability of the studies. Results An overview of 10 techniques found in 26 eligible articles focused on study protocols, research goals, and clinical outcomes is provided. Non-invasive techniques included laser speckle contrast imaging, micro-lightguide spectrophotometry, magnetic resonance imaging perfusion, near infrared spectroscopy, skin perfusion pressure, and plantar thermography. Invasive techniques included two dimensional perfusion angiography, contrast enhanced ultrasound, computed tomography perfusion imaging, and indocyanine green angiography. The results of the 26 eligible studies, which were mostly of poor quality according to QUADAS-2, were without exception, not sufficient to substantiate implementation in daily clinical practice. Conclusion This systematic review provides an overview of 10 tissue perfusion assessment techniques for patients with PAD. It seems too early to appoint one of them as a reference standard. The scope of future research in this domain should therefore focus on clinical accuracy, reliability, and validation of the techniques.

INTRODUCTION: Hyperspectral imaging (HSI) is a noninvasive technique for transcutaneous measurements of tissue perfusion. This study (1) provides a review of the current literature on HSI for tissue perfusion measurements of the lower leg and (2) introduces a standardized measurement protocol for HSI measurements with a portable system. EVIDENCE ACQUISITION: A literature search was performed for studies on tissue perfusion measurements with HSI in the lower extremity. A standardized protocol was developed to perform HSI measurements in 43 healthy volunteers at the plantar side of the foot and at the lateral side of the calf, with 3 consecutive hyperspectral images at each location. EVIDENCE SYNTHESIS: The literature review identified 9 studies, including 2 of healthy volunteers. 4 of patients with diabetes mellitus, and 3 of patients with peripheral arterial disease. In 5 of 7 patient studies, HSI values were associated with severity of disease or wound healing. In our study, the healthy volunteers' I ISI values for oxyhemoglobin, deoxyhemoglobin, and oxygen saturation were (mean +/- SD) 82.8 +/- 24, 55.7 +/- 15.7, and 59.2 +/- 11.7, respectively, at the plantar surface of the foot, and 40.8 +/- 11, 38.0 +/- 7.8, and 51.7 +/- 10.5, respectively, at the lateral side of the calf. HSI values differed significantly between the calf and plantar locations. Intraoperator reliability between the 3 consecutive images ranged from 81% to 89%. CONCLUSIONS: Limited evidence indicates that HSI is associated with severity of peripheral arterial disease and diabetes mellitus, and with wound healing. Hyperspectral images with a portable system can be taken with high precision when a standardized measurement protocol is used. However, differences exist at several locations at the lower extremity, so each measurement location should be used as its own reference when consecutive measurements are performed during follow-up. More studies with larger patient cohorts should be performed before HSI can be incorporated as standard tool in the diagnostic armamentarium of the vascular specialist.