Effect of contralateral severe stenosis or carotid occlusion on duplex criteria of ipsilateral stenoses: Comparative study of various duplex parameters

Purpose: This study compares the accuracy of various duplex parameters in grading ipsilateral carotid stenoses in patients with contralateral severe stenoses or occlusion. Methods: Four duplex criteria were correlated to arteriography in 356 carotid arteries in blind fashion: (1) standard criteria: a peak systolic frequency (PSE) of the internal carotid artery (ICA) of greater than or equal to 4 KHz was used to diagnose greater than or equal to 50% stenosis; (2) new criteria: a PSF of the ICA of greater than or equal to 4.5 kHz was used; (3) Fujitani criteria: a PSF of the ICA of >4.5 kHz and an end-diastolic frequency of <5.0 kHz was used; (4) internal carotid/common carotid artery (ICA/CCA) PSF ratio of greater than or equal to 1.5 was used. Results: The standard method overestimated 56 (16%) of 356 stenoses in contrast to 3% for the new method (p < 0.001), and this effect was most evident in the 50% to < 80% stenosis category (30%). The Fujitani method underestimated 97 (27%) of 356 stenoses, and the ICA/CCA ratio overestimated stenoses in 77 (22%) of 356. The overall exact correlation was 94%, 82%, 70%, and 75% for the new, standard, Fujitani, and ICA/CCA ratio, respectively. The kappa statistic and corresponding confidence intervals for the new method (kappa = 0.923, +/- 0.016) are significantly higher (p < 0.001) than those for the standard method (kappa = 0.760, +/- 0.027), the Fujitani method (kappa = 0.608, +/- 0.031), and the ICA/CCA ratio method (kappa = 0.642, +/- 0.051). The overall accuracy in diagnosing greater than or equal to 50% ipsilateral stenosis in the whole series was 85% for the standard method, 97% for the new method, 95% for the Fujitani method, and 81% for the ICA/CCA ratio. The new method was superior to the standard and ICA/CCA ratio methods (p < 0.001) and the Fujitani method (p = 0.024). Conclusions: The presence of significant contralateral stenosis (greater than or equal to 50%) can lead to overestimation of ipsilateral stenosis if the standard criteria are used; however, this problem can be avoided by using a PSF of the ICA of greater than or equal to 4.5 kHz for the diagnosis of greater than or equal to 50% stenosis.