Superficial femoral artery plaque, the ankle-brachial index, and leg symptoms in peripheral arterial disease: the walking and leg circulation study (WALCS) III

Abstract

Background: The clinical significance of magnetic resonance-imaged plaque characteristics in the superficial femoral artery (SFA) is not well established. We studied associations of the ankle-brachial index (ABI) and leg symptoms with MRI-measured plaque area and percent lumen area in the SFA in participants with and without lower-extremity peripheral arterial disease (PAD).

Methods and results: Four hundred twenty-seven participants (393 with PAD) underwent plaque imaging of the first 30 mm of the SFA. Twelve 2.5-mm cross-sectional images of the SFA were obtained. Outcomes were normalized plaque area, adjusted for artery size (0 to 1 scale, 1=greatest plaque), and lumen area, expressed as a percent of the total artery area. Adjusting for age, sex, race, smoking, statins, cholesterol, and other covariates, lower ABI values were associated with higher normalized mean plaque area (ABI <0.50:0.79; ABI 0.50 to 0.69:0.73; ABI 0.70 to 0.89:0.65; ABI 0.90 to 0.99:0.62; ABI 1.00 to 1.09:0.48; ABI 1.10 to 1.30:0.47 (P trend <0.001)) and smaller mean percent lumen area (P trend <0.001). Compared with PAD participants with intermittent claudication, asymptomatic PAD participants had lower normalized mean plaque area (0.72 versus 0.65, P=0.005) and larger mean percent lumen area (0.30 versus 0.36, P=0.01), adjusting for the ABI and other confounders.

Conclusions: Lower ABI values are associated with greater MRI-measured plaque burden and smaller lumen area in the first 30 mm of the SFA. Compared with PAD participants with claudication, asymptomatic PAD participants have smaller plaque area and larger lumen area in the SFA. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00520312.

Figures

Figure 1

A representative image of a participant with peripheral arterial disease. Panel a shows proton weighted MRI images TR/TE = 2160 ms/8 ms). Panel b shows time of flight images (TR/TE=38 ms/8.7ms). The blue contours define the outer wall area of the vessel. The red contours define the lumen boundary.

Figure 2. Associations of the Ankle Brachial Index with Mean Plaque Area (N=427)*

Unadjusted mean plaque area across ankle brachial index categories (N=427) Mean plaque area has been normalized for artery size by dividing average wall area by the median outer wall area normalized for artery size. *Data shown are means and standard deviations.

Figure 3. Associations of the Ankle Brachial Index with Mean Lumen Area (N=427)*

Unadjusted mean percent lumen area across ankle brachial index categories (N=427) *Data shown are means and standard deviations.