Validation of an angiographic method for estimating resting blood flow to distal tissue beds in the lower extremities

PURPOSE: The authors propose to validate an angiographic scoring system that estimates the resting blood flow in the lower extremities in patients with peripheral vascular disease (PVD). MATERIALS AND METHODS: Twenty patients with PVD underwent lower-extremity angiography. For each patient, three readers used the proposed scheme to estimate flow within 23 separate vessel segments from the infrarenal aorta to the pedal vessels. Each reviewer scored each angiogram twice. The scheme includes not only an assessment of stenoses and occlusions but also corrections for collaterals. Flow reductions to muscles in the thigh and calf were calculated by multiplying the estimated flows in the series of vessels that lead to these regions. The consistency of the scoring scheme was assessed by calculating Pearson correlation coefficients for intra- and interobserver variability. The scoring scheme was also used to estimate the ankle-brachial index (ABI) and these estimates were compared to the known ABIs. RESULTS: Overall, the scoring scheme demonstrated very good intra- and interobserver agreement. Correlation coefficients were typically greater than 0.9. In general, the correlation coefficients for proximal vessels were higher than those for distal vessels. The scoring scheme also had minimal intra- and interobserver variability for estimated flows to distal tissue beds. Agreement was better for a series of vessels than it was for individual segments. The estimated ABIs correlated well with the measured ABIs in all but two cases. These outliers include one case in which the measured ABI was >1 as a result of noncompressible vessels and the estimated ABI correctly reflected PVD. In the second case, the ABI was near normal because of a patent peroneal artery and our estimated ABI was abnormally low because our estimation method failed to factor in the peroneal artery. CONCLUSIONS: The proposed angiography scoring system reproducibly estimated flow reductions to distal tissue beds. The authors plan to use this system as a research tool for evaluating new methods of assessing and treating PVD.