Mechanisms That Produce the Leg Dysfunction of Claudication & Treatment Strategies

Study Overview
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Brief Summary
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Intermittent claudication afflicts 5% of the US population older than 55 years of age and develops along with hardening of the arteries of the legs. Claudicating patients limp and can only walk very short distances because their legs hurt. This protocol evaluates the mechanisms that may produce the leg dysfunction of claudication and its successful completion can ultimately produce significant new diagnostic and treatment strategies for the care of claudicating patients.

Detailed Description
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Claudication, defined as walking-induced leg discomfort and gait dysfunction relieved by rest, affects 5% of Americans over 55 years of age. Claudicating patients adopt sedentary lifestyles and cluster at the extreme low end of the physical activity spectrum, escalating risk for adverse health effects. The primary therapeutic goals for claudicating patients are restoration of leg function and prevention of disease progression. Current, rehabilitative interventions focus on inadequate blood flow as the only cause of claudication. Operative revascularization and/or exercise therapy are the principal conventional therapeutic modalities, providing only modest rehabilitative benefit. Applying biomechanical analysis to gait of claudicating patients, the investigators team has developed preliminary data indicating that blood flow is not the only mechanism producing the limb dysfunction of claudication. Several laboratories including the investigators own have demonstrated a myopathy, characterized by mitochondrial dysfunction, oxidative damage and inflammation, in leg skeletal muscle of claudicating patients. These conditions have not been quantified, comprehensively, in relation to claudication, and their association with severity of claudication is not known. The investigators hypothesis is that blood flow restriction is not a good predictor of limb dysfunction in claudication, whereas muscle mitochondrial dysfunction, oxidative damage and inflammation are strong predictors of limb dysfunction both at baseline and after conventional therapy with revascularization or supervised exercise. Under Aim #1, the investigators will acquire precise measurements of gastrocnemius mitochondrial function, oxidative damage and inflammation in claudicating patients, at the time of their initial presentation, and evaluate these measurements as predictors of objective measures of limb function and subjective measures of quality of life. Under Aims #2 and #3, the investigators will evaluate the effects of revascularization (Aim#2) and supervised exercise therapy (Aim#3) on mitochondrial dysfunction, oxidative damage and inflammation in claudicating gastrocnemius and on objective measures of limb function and subjective measures of quality of life. If the investigators hypothesis is correct, the work in Aim #2 will for the first time definitively demonstrate that blood flow restriction due to blockages in the arterial tree is not the only cause of claudication. The work under Aims #2 and #3 will determine whether revascularization or exercise therapy has a beneficial effect on the myopathy of claudicating muscle with associated improvement in limb function and quality of life. Finally, the proposed studies under Aims #1, #2 and #3 will provide quantitative modeling of a panel of mechanistic (bioenergetics, oxidative stress and inflammation) parameters as predictors of objective measurements of claudicating limb function and subjective measures of quality of life commonly used for clinical assessment. Measurements of gastrocnemius mitochondrial function, oxidative damage and inflammation may be useful tools that permit staging of disease for optimum intervention and evaluation of therapeutic interventions that specifically target these conditions, improving rehabilitative outcomes.

Official Title
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Mitochondrial Dysfunction, Oxidative Damage and Inflammation in Claudication

Conditions
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Peripheral Arterial Disease

Intervention / Treatment
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* Procedure: Revascularization Surgery
* Other: Supervised exercise therapy


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: a positive history of chronic claudication exercise-limiting claudication established by history and direct observation during a screening walking test administered by the evaluating vascular surgeon an ankle/brachial index < 0.90 at rest Exclusion Criteria: absence of Peripheral Arterial Disease (PAD) acute lower extremity ischemic event secondary to thromboembolic disease or acute trauma exercise capacity limited by conditions other than claudication including leg (joint/musculoskeletal, neurologic) and systemic (heart, lung disease) pathology
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Health Services Research
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: No Exercise Therapy or Revascularization operation<br>The patient is evaluated but no intervention | |
| Experimental: Revascularization Surgery<br>The patient undergoes surgery to revascularize the ischemic, symptomatic limb(s) | Other: Supervised exercise therapy<br> <br> |
| Experimental: Exercise Therapy<br>The patient undergoes supervised exercise therapy for 6 months | Procedure: Revascularization Surgery<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Walking distances | Initial Claudication Distance, Absolute Claudication Distance, 6-Minute Walking Distance | six months | 
| Quality of life Questionnaires | Walking Impairment Questionnaire and the Medical Outcomes Study Short Form 36 Healthy Survey | six months | 
| Leg biomechanics | Propulsion Impulse, Ankle plantarflexor torque, Ankle plantarflexor power and maximum isometric plantarflexion force | six months | 
| Leg hemodynamics | Ankle Brachial Index | 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Myofiber Mitochondrial Function | Mitochondrial Respiration measured via polarography | 6 months | 
| Myofiber Oxidative Damage | Myofiber content of HNE adducts and protein carbonyls. Muscle Manganese Superoxide Dismutase activity | 6 months | 
| Muscle inflammation | Expression of pro- and anti-inflammatory cytokines and monocyte/macrophage cell counts. | 6 months | 
| Myofiber Morphology | Cross-sectional area of the myofibers | 6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Peripheral Arterial Disease, Peripheral Vascular Disease, Claudication, Myopathy, Oxidative stress, Mitochondrial dysfunction, Biomechanics, Inflammation