Upper vs lower extremity arterial function after spinal cord injury

Abstract

Background/objective: The purpose of the study was to determine whether arterial diameter, flow-mediated dilatation (FMD), and arterial range are affected by spinal cord injury (SCI). We assessed arm (radial) and leg (posterior-tibial) arteries that are comparable in size and function to determine whether (a) arterial function is reduced in individuals with SCI vs nondisabled subjects and (b) decrements to SCI arterial function are greater in the legs vs arms.

Participants: Eighteen men with chronic (9.8 +/- 6.3 years) SCI (T2 to T11; American Spinal Injury Association A) and 13 nondisabled subjects matched for age (33.1 +/- 4.8 vs 29.8 +/- 8.2 years old, respectively), height, and weight (BMI = 25.3 +/- 5.8 vs 26.6 +/- 5.5 kg/m2, respectively).

Methods: Radial and posterior tibial artery B-mode ultrasound images were continuously captured to measure resting diameter, occluded diameter, and postischemic diameters. Hierarchical linear modeling accounted for the nested experimental design.

Results: Individuals with SCI have lower systemic (arm + leg) FMD than nondisabled subjects (9.3% vs 12.3%, respectively; P= 0.035), primarily because of reduced leg FMD (11.5 +/- 3.1% vs 7.0 +/- 2.8% for SCI arms vs legs, respectively; P = 0.010). Persons with SCI also had lower arterial range than nondisabled subjects (0.79 vs 1.00 mm, respectively; P = 0.043), primarily because of the legs (0.81 +/- 0.09 vs 0.56 +/- 0.11 mm for SCI arms vs legs, respectively; P = 0.030).

Conclusion: Leg arterial function seems to deteriorate at greater rates compared to the arms for individuals with SCI. Interventions to improve cardiovascular health should include measurements taken in the legs.

Figure 1. Examples of the image analysis for measuring arterial diameters. B-mode images of (A) resting, (B) minimum, and (C) maximum diameters are shown. (Bottom) Representative plot of arterial diameter in response to 10 minutes of proximal ischemia. Images were captured at a rate of 30 images per second. Arterial range was calculated by subtracting the minimum diameter from the maximum diameter.

Figure 2. FMD and arterial range measurements as absolute diameters in the arms and legs of individuals with SCI and nondisabled individuals. (A) Original data for FMD represented by the absolute diameter size after 5 minutes of ischemia. (B) Original data for arterial range. (C) HLM FMD transformed data accounting for differences in resting diameter. (D) HLM arterial range transformed data accounting for differences in resting diameter. *P < 0.05, within-group differences between arm and leg scores. Original data shown in A and B are mean and SD. The HLM model-fit values are mean and SE and correspond to models shown in Tables 4 and 5.

Figure 3. (A) FMD and (B) arterial range plotted against years of SCI injury. Nondisabled subjects are dummy-coded to have 0 years of injury. Values correspond to models shown in Tables 5 and 6.