Clinical correlates of size and number of collateral vessels in peripheral artery disease

We studied associations of the number and size of magnetic resonance angiography (MRA)-assessed lower extremity collateral vessels with the ankle-brachial index (ABI), severity of superficial femoral artery (SFA) plaque, and leg symptoms in participants with peripheral artery disease (PAD). A total of 303 participants with PAD underwent time-resolved MRA at the thigh station. Collaterals were categorized by number (Category 1: 0-3 collaterals; Category 2: 4-7 collaterals; Category 3: ≥ 8 collateral vessels) and size (Grade 1: ≤ 5 small collaterals; Grade 2: > 5 small vessels; Grade 3: ≤ 5 large collaterals; Grade 4: > 5 large collaterals). Adjusting for age, sex, race, comorbidities and other covariates, more numerous collateral vessels were associated with lower ABI values (Category 1: 0.79; Category 2: 0.67; Category 3: 0.60; p trend < 0.001). Similarly, larger collateral vessels were associated with lower ABI values (Grade 1: 0.75; Grade 2: 0.65; Grade 3: 0.62; Grade 4: 0.59; p trend < 0.001). More numerous (p < 0.001) and larger (p < 0.001) collateral vessels were associated with greater mean SFA plaque area (p trend < 0.001). More numerous (p trend = 0.007) and larger (p trend = 0.017) collateral vessels were associated with a lower prevalence of asymptomatic PAD. In conclusion, among participants with PAD, larger and more numerous collaterals, measured by MRA, were associated with lower ABI values, greater plaque area in the SFA, and a lower prevalence of asymptomatic PAD. Further study is needed to determine the role of collateral vessels in maintaining functional performance in PAD.