Invasive Methods of Diagnosing Acute and Chronic Venous Disease

Intravascular Ultrasonography

IVUS catheters are introduced into the venous system over guidewires, requiring either a 5-Fr sheath for imaging a field of view of approximately 24 mm diameter, or an 8-Fr sheath for a field of view of 60 mm. High-quality transcutaneous ultrasound imaging allows safe entry into many nonstandard venous access segments, including upper thigh femoral vein, greater saphenous vein, popliteal vein, posterior tibial vein, and brachial veins, with insertion of a 3-Fr catheter to answer specific but limited anatomic questions, or of a larger-caliber sheath to undertake venous interventions. Cannulation of these veins in many patients can proceed with relative safety even in the setting of international normalized ratios (INRs) in the range of 2.0 to 3.0, with the decision to do so resting on the purpose of the procedure and the ease of postoperative hemostasis. In general, even large-caliber (9-Fr sheath) access into the internal jugular or greater saphenous veins of fully coumadinized patients has been safe in our experience, with due attention to postoperative hemostasis and postural and weight-lifting restrictions.

Intravascular ultrasound is unmatched in its comprehensive and sensitive demonstration of the cross section of a venous lumen. It is a common experience to demonstrate by IVUS a 50% or 75% cross-sectional narrowing in a venous channel that looks marginal or even acceptable by contrast venography. In a protracted venous recanalization, we find that the added expense of intravascular ultrasound is justified by its return of accurate and valuable anatomic information complementing the flow evaluation of contrast venography, leading to more consistent and more confident decisions regarding whether to stent or not stent or whether to add a flow-enhancing procedure such as venous thrombectomy or construction of an arteriovenous fistula to a recanalization procedure.

Finally, IVUS is often necessary to answer specific and limited anatomic questions, such as whether a prophylactic filter contains postprocedural clot burden, whether the contralateral transfemoral guidewire is inside or outside an IVC stent, or to confirm the level of a known anatomic structure. Often IVUS can answer such limited anatomic questions conclusively without the incremental burden of contrast material or irradiation entailed by a contrast venogram.