Background: Previous studies comparing paretic limb blood flow with the unaffected limb have been contradictory and have often omitted comparisons of peak reactive hyperemic flow. Our objective was to perform bilateral measurements of resting and reactive hyperemic blood flow in the lower legs of chronic (>6 months) stroke patients. A secondary purpose was to determine the extent to which any unilateral changes in limb blood flow were a function of decreases in lean tissue mass on the affected side. We hypothesized that the chronic hemiparesis accompanying ischemic stroke creates an altered metabolic environment in the tissues of the affected side that ultimately impairs vasomotor function.
Methods: The study used a single-visit cross-sectional design. All tests were performed at the Baltimore VA Medical Center. Nineteen chronic hemiparetic stroke patients (15 male, 4 female) who had mild to moderate hemiparetic gait after ischemic stroke were recruited for observation. Bilateral measurements of resting and reactive hyperemic blood flow were made using venous occlusion strain gauge plethysmography. Paired t-tests were used for the between leg comparison. Regression analysis and analysis of covariance were utilized to determine the strength of the relationship between lower leg lean tissue mass and blood flow.
Results: Resting and reactive hyperemic blood flows were significantly reduced in the paretic compared with the non-paretic limb (32 and 35%, respectively, p < 0.001). Lean tissue mass was also significantly lower in the affected limb (p < 0.01). However, neither resting nor reactive hyperemic blood flows were significantly correlated with lower leg lean tissue mass by dual energy X-ray absorptiometry. The difference in blood flow between limbs remained after covarying for lean tissue mass.
Conclusion: Hemiparesis causes impairments in vasomotor function under both resting and hyperemic conditions that are independent of the muscle atrophy on the affected side.