Calf Muscle Perfusion in Patients With Intermittent Claudication by Non-invasive MSOT

The objective of the proposed study is to define independent parameters for the diagnostic assessment of the perfusion situation of the calf muscle based on multispectral optoacoustic tomography (MSOT) in a cross-sectional collective of patients with PAD in Fontaine stage II (intermittent claudication) and a healthy control collective (study group 1). The results will be validated using an independent validation group (study group 2).

PAD is one of the most common diseases of the elderly. As life expectancy increases, there is a growing need for new treatment concepts and new diagnostic procedures.

Up to now, only the measurement of macrocirculation in the form of CCDS, ABI and measurement of the actual walking distance are available as independent validation measures of revascularization methods (endovascular/open). The S3 guideline for diagnosis, therapy and medical aftercare of PAD published in 2015 by DGA (Deutsche Gesellschaft für Angiologie, German Society for Angiology) recommends such aftercare examinations, especially for patients that underwent vascular surgery. However, for the mentioned validation measures there are some patient groups for which these methods provide only insufficient or unusable results (e.g. diabetes mellitus, terminal renal failure). In these cases, independent verification of the success of the chosen therapy would have to be performed using angiography (digital subtraction angiography, CT angiography or MR angiography). However, this is not routinely performed in the respective patient populations due to the associated risks (including radiation exposure, contrast agent administration, invasiveness).

MSOT provides a new non-invasive diagnostic method that may be able to fill this diagnostic gap. A first study (MSOT_PAD, NCT04641091) confirmed the hypothesis that data collected via MSOT examination of the calf muscle can be used for PAD diagnostics. The derived concentration of oxygenated hemoglobin (HbO2) proved to be the most suitable measurement parameter. A connection could be established between the measured HbO2 concentration and the clinical stage of PAD. Differentiation improved after a standardized exercise of a walking distance of 150 meters, with patients in the stage of intermittent claudication (IC, Fontaine stage II) being more difficult to differentiate in comparison to patients in Fontaine stages III and IV.

The aim of this cross-sectional study is to increase the sensitivity and specificity of the procedure for IC patients by using a more suitable exercise between first and second MSOT measurement, namely repeated heel raises until the occurrence of claudication pain. A subgroup of the IC patients having been included in the study will be asked to undergo the study protocol a second time after interventional/ surgical revascularization. This is to investigate whether and how the improved blood flow situation translates to the measured MSOT parameters.

As additional target variables, the relative, absolute and total walking distance in a 6-minute walk test as well as the PAD-specific quality of life will be recorded with the VASCUQOL-6 questionnaire. A healthy control collective is included as a comparison group.

Eligibility Criteria:
Inclusion Criteria:

* Patients with manifest PAD in stage II according to Fontaine or categories 1-3 according to Rutherford or healthy volunteers
* Adults (\>18 years) who are able to give their consent

Exclusion Criteria:

* Patients with PAD stage I, III and IV according to Fontaine or categories 0, 4, 5 and 6 according to Rutherford or healthy volunteers with diabetes mellitus, chronic renal failure, claudication symptoms, abnormal ABI or non-palpable foot pulses
* Underage persons
* Lack of written consent
* Safety concerns of the study physician (person with physical, mental or psychiatric conditions which, by the judgement of the study physician, would compromise the person's safety or the quality of the data, thereby rendering the person an ineligible candidate for the study)