Purpose: The purpose of this study was the comparison of intravascular ultrasound scanning (IVT-TS) with transfemoral venography in the assessment of chronic iliac vein obstruction. Methods: IVUS and standard, single-plane, transfemoral venography were performed in 304 consecutive limbs during balloon dilation and stenting of an obstructed iliac venous segment. The appearance of the obstruction was described, arid the degree of stenosis (maximal diameter reduction) was estimated with venography and IVUS. The stenotic area was derived with diameter calculations (pir(2)) and also was measured with the built-in software of the IVUS apparatus before and after dilation and stenting in 173 limbs. Preoperative hand/foot differential pressure and preoperative dorsal foot venous and intraoperative transfemoral hyperemia-induced pressure elevations after intra-arterial injection of papaverine hydrochloride were measured. Results: With IVUS, fine intraluminal and mural details were detected (eg, trabeculation, frozen valves, mural thickness, and outside compression) that were not seen with venography. The median stenosis (with diameter reduction) on venographic results was 50% (range, 0 to 100%) and on IVUS results was 80% (range, 25% to 100%). In a comparison with IVUS as the standard, venography had poor sensitivity (45%) and negative predictive value (49%) in the detection of a venous area stenosis of >70%. The actual stenotic area was more severe when measured directly with IVUS (0.31 cm(2); range, 0 to 1.68 cm(2)) versus derived (0.36 cm(2); range, 0 to 3.08 cm(2); p <.001), probably as a result of the non-circular lumen geometry of the stenosis. No correlation was found between any of the preoperative or intraoperative pressure measurements and degree of stenosis with or without collaterals. When collaterals were present, a more severe stenosis (median, 85%; range, 25% to 100%) was observed (versus a 70% stenosis in the absence of collaterals; range, 30% to 99%; P <.001), along with actual stenotic area (with collaterals: median, 0.24 cm(2); range, 0 to 1.18 cm(2); without collaterals: median, 0.45 cm(2); range, 0.02 to 1.68 cm(2); p <.0 1) and a higher rate of hyperemia-induced pressure gradient (2:2 min Hg; with collaterals, 34%; without collaterals, 11 %; P <.0 5). Conclusion: Venous IVUS appears to be superior to single-plane venography for the morphologic diagnosis of iliac venous outflow obstruction and is an invaluable assistance in the accurate placement of venous stents after venoplasty. No preoperative or intraoperative pressure test appears to adequately measure the hemodynamic significance of the stenosis. In lieu of adequate hemodynamic tests, IVUS determination of morphologically significant stenosis appears to be presently the best available method for the diagnosis of clinically important chronic iliac vein obstruction. Collateral formation should perhaps be looked on as an indicator of a more severe stenosis, although significant obstruction may exist with no collateral formation.
