Ankle-Brachial Index Changes Post Exercise and Its Effects on Patient-Centered Outcomes and Gait

The purpose of this study is to examine if dynamic, exercise induced changes in the ankle- brachial index (ABI) are associated with pain, quality of life, and functional outcomes to better characterize peripheral vascular disease.

Individuals will be screened for eligibility if they meet the inclusion criteria. All data collection will occur during a single laboratory visit. It is anticipated the research study will take 1-2 hours, with 1 visit total to complete the study.

The primary study endpoint is to assess the use of the ankle-brachial test after exercise. This will be accomplished when the proposed number of subjects have been enrolled and completed the proposed protocol. Secondarily, the study may be stopped due to lack of funding. The final endpoint will be the completion of all data analysis including long-term follow up data and preparation for dissemination of the research findings.

The primary safety endpoint will occur if the study participant is unable to complete any part of the protocol.

All participants will give written consent to participate in the study. Participants will be instructed to refrain from alcohol, caffeine, nicotine, and exercise for at least one hour prior to testing to minimize confounding physiological effects. Testing will occur in a temperature-controlled environment maintained between 74-78°F (23-26°C) to ensure thermal stability and vascular consistency. Participant information including age, body mass index (BMI), diabetes status, past medical history, smoking history, and a list of current medications will be collected.

Participants will be comfortably positioned supine with the head of bed flat and legs fully extended. A 10-minute rest period will precede the initial ABI test to allow for hemodynamic stabilization.

For all ABI measurements, systolic blood pressures will be measured at the brachial and dorsalis pedis or posterior tibial arteries in both lower extremities using a hand-held 8-10 MHz continuous wave Doppler ultrasound probe (Huntleigh or equivalent) and appropriately sized sphygmomanometer cuffs. See Appendix A for ABI procedure details.

The order of arterial site measurements for initial resting ABI will be determined using a computer-generated randomization schedule. The limb exhibiting the lowest resting ABI will be selected for inclusion in the statistical analysis. The ABI will be calculated as the ratio of the higher ankle systolic pressure (either dorsalis pedis or posterior tibial) to the higher brachial systolic pressure (left or right arm). All data will be recorded to the nearest 2 mmHg.

Participants will then complete a 6-minute walk test, up to max pain on the 1 to 5 Claudication Symptom Rating Scale, to elicit claudication symptoms. ABI immediately post-exercise and at 1-, 3-, and 5-minute recovery intervals will be assessed in the same position as the resting ABI.

A participant will be considered to have completed the study after participating in the single visit. No in person follow up visits are anticipated.

Demographic history and SF-36 questionnaire may be collected by phone if needed.

Participation in this study is completely voluntary, and subjects can withdraw at any time. No specimens are associated with this study. All data will be stored according to study and subject number on an LSU network server. Electronic data and analysis will be retained for a minimum of seven years after study closure, and indefinitely after that.

Standard research practices will be used to document informed consent and schedule study visits. Consented subjects will be assigned a study number. A subject log relating subject name and subject number will be maintained by study personnel on a secure computer workstation by Dr Murnane in the School of Health Professions. Original signed and dated documents for all subjects will be securely maintained in the School of Health Professions.

A research team member will contact and discuss the study with potential participants to assess his/her interest in participating. The study design outlines methods of ensuring ongoing consent. Formal consent and signing of the consent form will occur in the School of Allied Health Professions or vascular clinic at Ochsner LSU Health Shreveport with a member of the study team before any testing begins.

Subjects will have the opportunity to ask questions and decline participation in this study. A copy of the informed consent will be provided to the subject.

Inclusion criteria

• individuals over 65 years of age
• individuals aged 50-64 with a risk factor for atherosclerosis including diabetes mellitus, history of smoking, hyperlipidemia, hypertension, or family history of peripheral arterial disease (PAD)
• individuals aged 18-50 with diabetes mellitus and one additional risk factor for atherosclerosis as noted above, or
• individuals with known atherosclerotic disease in another vascular bed including the coronary, carotid, subclavian, renal, or mesenteric artery stenosis, and individuals with known PAD

Exclusion criteria

• contraindications to brachial and/or ankle pressure measurement including history of deep vein thrombosis
• lymphedema of the arms or legs
• history of mastectomy or current leg ulceration preventing placement of a blood pressure cuff around the lower leg
• an inability to lie in a supine position for 15 min
• self-reported inability to walk for 6 minutes
• severe cardiac or pulmonary disease limiting exercise
• inability to obtain a Dopplerable pulse
• noncompressible arteries (ABI >1.4)
• those unable to consent