To the Editor.—The article by Corson et al in the August 1978 issue (113:932-935) bears comment relative to their finding of no correlation between the ankle systolic pressure index (ankle pressure divided by brachial pressure) and the incidence of early failure of saphenous vein grafts. The authors have correctly quoted our article1 showing a highly significant correlation between low ankle pressure indices (<0.20) and early thrombosis of femoropopliteal bypasses. Comparison of the study by Corson et al with ours, however, is inappropriate, for the authors included 20 patients who had bypass grafts that extended beyond the popliteal artery to distal vessels. The inclusion of this subgroup without clarification of their ankle systolic pressure indices makes comment regarding the contrasting resuits of their study and ours inappropriate.
It can be argued that the ankle pressure indices in the 20 patients who had distal bypasses were probably concentrated in the