Duplex velocity characteristics of aortoiliac stenoses.

PURPOSE

It is now possible to grade aortoiliac stenoses in broad categories based on peak systolic velocity (PSV) changes. The goal of this study was to see whether additional simple Doppler parameters would improve the grading of aortoiliac obstructive disease.

METHODS

Duplex parameters were compared in 112 aortoiliac segments with four categories of arteriographic diameter reduction and four categories of common femoral artery pressure measurements. These parameters were PSV, PSV ratio, PSV difference, end diastolic velocity (EDV), the presence or absence of reverse flow, and the presence or absence of spectral broadening.

RESULTS

The discriminative value of the PSV ratio was better than that of either the absolute PSV value or the PSV difference. A PSV ratio < 1.5 combined with reverse flow and a clear systolic window in the Doppler spectrum predicted a diameter reduction < 20% (sensitivity, 100%; specificity, 58%; positive predictive value [PPV], 89%; negative predictive value [NPV], 100%; accuracy, 90%). For the detection of > or = 50% aortoiliac stenoses, a PSV ratio > or = 2.8 provided 86% sensitivity and 84% specificity (PPV, 84%; NPV, 85%, accuracy, 85%). An absolute PSV value of 200 cm/sec has a high sensitivity (95%) but a low specificity (55%) in identifying > or = 50% stenoses (PPV, 68%; NPV, 91%; accuracy 75%). An EDV > 0 cm/sec at the stenosis indicates a femorobrachial pressure index < 0.90 with 51% sensitivity and 89% specificity. An EDV > or = 40 cm/sec indicates a femorobrachial index < 0.80 with 50% sensitivity and 89% specificity, and indicates > or = 75% arteriographic stenoses with 70% sensitivity and 90% specificity (PPV, 64%; NPV, 92%; accuracy, 86%). A stenosis > or = 75% was also identified by a PSV ratio of 5.0 with 65% sensitivity and 91% specificity (PPV, 65%; NPV, 91%; accuracy, 86%).

CONCLUSIONS

The PSV ratio is the most important parameter to grade aortoiliac stenoses into < 20%, 20% to 49%, 50% to 74%, and 75% to 99% categories, but additional parameters such as absolute PSV value, EDV, and the presence or absence of reverse flow and spectral broadening in the Doppler spectrum are helpful in gradation.