[Amelioration of the diagnostic possibilities of irrigraphy by a new index, I0]

Irrigraphie (segmental impedance plethysmography) is a reliable non invasive method for the positive and topographic diagnosis of arterial occlusive disease and for its prognosis (5, 8, 9, 12, 13). The method is based on pulse volume recordings at six different positions of the leg (from 1 = proximal to 6 = distal). The amplitude of the signal is related to heart rate and to the basic impedance of the segment of the leg. The diagnosis of aorto-iliac disease is proposed when the upper extremity index (I1MS) over the lower extremity proximal index (I1) ratio (ITA) is increased (greater than 1.4), or when the I1 value is lower than 1.9. The diagnosis of femoro-popliteal disease is proposed when there is a significant drop between I1 and the above knee index I3. However in a recent study we found that I1 value drops when there is a severe femoro-popliteal lesion. In this case, irrigraphie proposes erroneously the diagnosis of aorto-iliac and femoro-popliteal diseases. In order to improve the method, we thought that a new electrod position (I0) over the iliac region would give to irrigraphie a more reliable topography diagnosis possibility. In this study 32 patients were analysed with angiography and irrigraphy, and divided into 3 groups: group I = isolated iliac disease (19); group F = isolated femoral diseases (22); group IF = ilio-femoral diseases (12). We observe from the ROC analysis, that I0 has a sensitivity of 84% and a specificity of 86%, when the iliac lesions are isolated whereas I1 and ITA give a lower specificity (52%). However, when aorto-iliac lesions are combined with femoro-popliteal lesions the irrigraphie is a little less sensitive (71%). In conclusion I0 index is more reliable for the topographical diagnosis of obstructive disease of the iliac artery than I1 index and we suggest to replace I1 by I0 whenever it is possible.