Abstract
In 2000, when our group published in JEVT the first large report on iliac vein stenting, 1 Dr. John Bergan commented that this technique was a major step forward in the management of chronic venous occlusion. 2 The report by Kölbel et al. 3 in the current issue of JEVT is further evidence that his statement was true and follows later supportive reports from our group 4 and others.5,6 While stenting has replaced bypass surgery for iliac artery stenoses and occlusions, venous stenting has been slow to be widely adopted despite its availability and successful use for more than 10 years. The reasons for this are several. The main obstacle is the general focus on venous reflux and the poor understanding of the importance of venous outflow obstruction in the pathophysiology of primary and secondary chronic venous disease, coupled with the sole reliance on infrainguinal duplex Doppler studies for diagnosis of the lower limb venous system. Increased awareness of the importance of a venous outflow obstruction among the treating physicians is the key. Granted, it is not known at what percentage a venous stenosis becomes critical, and accurate noninvasive or invasive hemodynamic tests are therefore not available. While a positive test supports further investigations, a negative cannot exclude the presence of a significant obstruction. The diagnosis of occlusive or non-occlusive obstruction is, therefore, based on morphological studies (>50% stenosis is considered significant, which has been arbitrarily chosen based on clinical outcome). Since ultrasound scanning of the pelvic outflow is suboptimal in the detection of obstruction, venography (transfemoral, magnetic resonance, or computed tomography), should be performed in patients with severe chronic venous insufficiency (CEAP class C3–6).
The ultimate arbitrator is intravascular ultrasound (IVUS). Iliofemoral IVUS should be generously applied when there is suspicion of obstruction, collaterals are revealed on other morphological tests, or hemodynamic measurements suggest outflow obstruction. Selection of patients for intervention will be based on symptom severity and morphological assessment until a hemodynamically reliable test has been found.
The authors have presented a high immediate success rate and a sustained cumulative patency at least up to 6 years post-stenting. The duration of the occlusion, presence of thrombophilia, or the need to extend the stenting beneath the inguinal ligament into the common femoral vein did not worsen the patency rate, which is in accord with other experiences.4,7 It is an important observation since many interventionists refuse to attempt recanalization in patients with thrombophilia and extensive “old” chronic obstructions. The authors have shown this position to be a mistake.
The authors emphasize the importance of inflow to the stent system, and I agree that this is crucial for long-term stent patency. It is, however, difficult to assess whether or not there is sufficient inflow into the stent system prior to the procedure, and it is easy to be too restrictive in the selection of patients. The patient is rarely worse off clinically compared to pre-intervention even if the procedure fails or the stent later occludes. The extent of disease to be allowed in the femoropopliteal and profunda vein segments to ensure stent patency is not defined. The inflow to the common femoral vein segment is usually greater than visualized. The importance of the profunda vein inflow is usually underestimated; it is crucial to identify the phenomenon of axial profunda transformation and presence of a connection between the profunda and popliteal veins following femoral deep venous thrombosis. 8 When this connection is found, the profunda vein can be accessed from below and the stent placed into the profunda vein in the presence of an occluded femoral vein.
“There are many ways to skin a cat” the saying goes. The techniques of stenting vary. The authors have obviously been very successful using initial jugular vein cannulation, multiple accesses, and snaring techniques in the majority of cases; in over half of these procedures, a second access was performed in the ipsilateral lower limb below the obstruction. Contrary to the authors, we initially access the obstruction from below, usually via an ultrasound-guided cannulation of the femoral or profunda vein in the thigh area, which places the access site close to the obstruction and allows better “pushability.” We rarely need to use any additional access sites. 9 When the common iliac vein is occluded, we have found it exceedingly difficult to recanalize from above. When it is only partially obstructed (allowing access from above), even in the presence of lower iliac segmental occlusion, the recanalization success rate from the ipsilateral caudal access site alone is successful in almost all patients. I would suggest that in order to limit the number of access sites one should initially use ipsilateral thigh cannulation and then, if necessary, proceed with additional sites.
I would also emphasize the use of IVUS to guide stent placement. On average, the venogram underestimates the degree of stenosis by 30%. Using the axial IVUS image, the degree of obstruction can be accurately measured by planimetry and is invariably found to be more extensive than shown by venography. The appropriate diameter and length of the stent can be determined. As pointed out by the authors, it is crucial to cover the entire lesion, in both non-occlusive and occlusive disease, to ensure long-term stent patency. The cephalad and caudal endpoints of stenting can be adequately evaluated only by IVUS, which better visualizes the wall apposition of the stent and any recoil after stent insertion. We believe IVUS to be a vital tool in the diagnosis of morphological stenosis; moreover, stent placement must be guided by IVUS to achieve an optimal long-term result.
The study by Kölbel et al. 3 and the experiences of other investigators should stimulate physicians who treat severe chronic venous insufficiency (C3–6) to combine duplex ultrasound scanning with iliofemoral outflow imaging. When morphological non-occlusive obstruction or occlusion is suggested, they should consider IVUS-guided iliocaval stenting.