A Case of Muscle Contraction-Induced Ischemic Limb Hyperemia in a Patient with Peripheral Arterial Disease during Incremental Repeat Isometric Knee Extensor Workloads

Background: To determine whether muscle contraction-induced leg blood flow (LBF) during exercise may be altered in a patient with an ischemic limb due to peripheral arterial disease (PAD) compared with the non-PAD limb. Case Presentation: A 66-year-old male patient with intermittent claudication due to PAD in the right leg (ankle brachial pressure index, 0.69) showed complete obstruction in both common iliac arteries including internal/external segments with collaterals above the femoral artery and popliteal artery with collaterals, and in the healthy left non-PAD-leg (1.06). He attempted unilateral repeat isometric knee extensions at a target contraction rhythm with each leg at incremental contraction intensities (5%, 10%, and 30% of maximum voluntary contraction [MVC] for 3 min at each intensity). Blood velocity/flow (Doppler ultrasound) in the femoral artery, blood pressure, and leg vascular conductance (LVC) were measured. Isometric thigh MVC strength pre-exercise was similar between the PAD-leg (48.0 kg) and non-PAD-leg (48.7 kg). Pre-exercise LBF (ml/min) was also similar between the PAD-leg (316) and non-PAD-leg (327). Blood pressure increases were similar during exercise. Average exercising LBF in ml/min in the last 1 min at each intensity was higher in the PAD-leg than the non-PAD-leg: 1087 vs. 471 at 5%, 2097 vs. 712 at 10%, and 2656 vs. 1517 at 30% MVC with a close positive linear relationship between LBF and %MVC in the non-PAD-leg (r = 0.999, P < 0.01), in agreement with previous findings, but less significant in the PAD-leg (r = 0.879, P = NS), indicating intense vasodilation (increasing LVC) in the PAD-leg compared with the non-PAD-leg. Conclusion: Knee extensor exercising LBF in the femoral artery was dissimilar between the PAD-leg and non-PAD-leg at the same exercise intensity, even though pre-exercising LBF was the same. Further research on the time-course in hemodynamics during leg exercise in PAD might potentially provide insight for the cardiovascular adjustment in severity of arteriosclerosis, stenosis and/or collaterals reserve.