Rapid thrombus removal is the first-line treatment for acute LEDVT19,20, as it can reduce the risk of complications at both the acute and chronic stages including Pes and PTS. Endovascular techniques have emerged as an advantageous approach to acute DVT treatment15, but the selection of an appropriate access route is essential to the success of this procedure. The results of the present study confirmed that the CDVs represent feasible and safe access routes for the endovascular treatment of DVT that can provide patients with a good level of perioperative comfort.
The use of the superficial calf veins as an access route for thrombolysis catheter placement in DVT was first described in 1996 by Cragg et al. 21. The SSV has been frequently used as an access via puncture or incision18, and it has even been used as an access for thrombus suction devices in recent years22. However, the SSV exhibits unique characteristics including an anatomic relationship with the sural nerves 23,24, contributing to potential procedural complications, particularly in patients in whom incision is performed. Numbness of the area innervated by damaged sural nerves is a relatively common complication that affects ~ 10% of patients22. The access route in most patients in the NDCDVP group in this study was the SSV, and about 13% of patients experienced numbness of the calf skin. This rate was significantly lower in the DCVP group, primarily as no incision was performed, thus avoiding damage to the sural nerves. Anatomical variations of the SSV are also common. Over 20% of SSVs do not empty into the PV, instead emptying into the GSV or femoral vein 22,23. The SSV is thus not an effective access if clots have spread to the PV as it can be difficult for the thrombolysis catheter or thrombus suction devices to reach the thrombotic segment. Positional change is also often necessary for incisions made during the operation, and thrombolytic or anticoagulant drugs are administered during the treatment period, increasing rates of complications such as local bleeding, hematoma, and infection. Rates of these complications were low in the DCVP group, potentially owing to the absence of any incision or position change and to the east of care for the selected access sites.
The PV is also frequently used as an access route for the CDT and PMT treatment of DVT cases 25. As this vein is located on the back of the body proximal to the popliteal artery and tibial nerve in the popliteal fossa, which is composed of loose connective tissue, ultrasound guidance is routinely needed to maximize the success of puncture via this route while minimizing complication rates. Even so, patients can experience complications including nerve injuries and pseudo-aneurysm6,26, and many need to turn from the prone to the supine position during this procedure, potentially causing discomfort while increasing the work for medical staff. This procedure can also be difficult for patients affected by fractures, paralysis, or who have just completed other operations. Recent surgery is a risk factor in 15–40% of DVT patients26,27, with 34% of patients in the present study having a history of recent surgery. In the DCVP group, the need for patients to change position was obviated, in line with results of another prior study 28. However, clots situated below the knee can be difficult to treat via this entry route.
Access via the contralateral femoral vein has also been reported6, but this procedure is associated with high failure rates. This may be due to the fact that the procedure is opposed to the valve direction, and left-sided LEDVTs are more common than right-sided ones26. As many LEDVTs co-occur with iliac vein compression syndrome, this can make it challenging to advance devices through this venous region. In the present study, 89% of patients with left-sided LEDVTs also exhibited iliac vein compression syndrome. Access via this route may also injure the valve, increasing the risk of post-thrombotic syndrome 29.
To overcome the above issues, CDVs were adopted as an access route for the endovascular treatment of DVT patients. Armon et al. first reported the use of PVT access for the CDT treatment of iliofemoral DVT in 1996, with further follow-up on this technique the following year 30. More recently, Bendix et al. analyzed outcomes from 27 DVT patients treated via thrombolysis with access via the PTV, comparing this route PPV access and thereby confirming that the PTV is a safe and effective access option for treating cases of iliofemoral and femoropopliteal28. ATV access has also been described by Wang et al. 26,31, who determined that this approach can be feasibly used for the safe and effective treatment of acute extensive LEDVT patients. Our institution began using CDV access as a standard approach when treating DVT patients beginning in 2012, with almost 500 patients having undergone treatment using this approach via the ATV, PTV, and PNV over the last decade. While the success rates in the NDCVP and DCVP groups in this study were similar, the rates of perioperative complications such as local infections and hematomas in the DCVP group were significantly lower, in line with prior results reported by Bendix et al. who observed negligible postprocedural local access site complications in their PTV access group28. There are six calf veins that can be used as an access route, necessitating the selection of the appropriate vein in a given patient. In the DCVP group in the present study, CDV access failed in 9 cases, most often due to a history of CDV thrombosis. The diameter of the CDVs will increase when the proximal region is obstructed by a clot, increasing vascular pressure such that a combination of X-ray and contrast guidance can enable relatively easy access. No ultrasound guidance was used in this study28, with DSA guidance being used in all cases. DSA guidance offers advantages over ultrasound monitoring, allowing for the dynamic monitoring of the puncture route (Video 1). Wang et al. reported several advantages associated with the ATV approach 31, including the lack of any need to change positions during the operation, allowing for the effective lysis of thrombi located in deep veins below the knee while preventing mechanical injury to the vein valve and thereby better preserving valve function. As such, the appropriate selection of the ATV, PTV, or PV is important (Video 2), providing a better means of lysing thrombi located below the knee. However, there are some disadvantages to CDV access. For one, large sheath implantation can injure the CDVs, and the distance is too great to enable the delivery of a stent from the access to the iliac vein if an iliac vein stent is required. In this study, an 8F sheath was not associated with local site complications, and when a larger sheath was required we were able to overcome any issues by additionally utilizing the ipsilateral femoral vein following the dissoluition of the target thrombi. Moreover, 6F is sufficient for the use of stents produced by Bard or Ev3 Company.
Several strategies can help improve the accuracy of CDV puncture, thereby minimizing the risk of multiple punctures or damage to nerves or arterial structures. We found venography to be necessary, with an appropriate contrast agent being injected via the indwelling needle in the dorsal vein of the foot while compressing superficial veins using an elastic bandage on the ankle (Fig. 1), thus allowing the confirmation of the extent of thrombus involvement and the selection of the most optimal CDV for use as an access route. The positioning of DSA guidance can then be modified to be parallel to the target vessel while avoiding the overlap of the target vessel and the bone in projections. A metal puncture needle represents the best choice for this procedure. The puncture direction must remain horizontal and parallel to the target vessel and vertical with the plate of DSA in the vertical direction, with the needle head being in the middle of the target vein in projections (Video 1).
There are some limitations to this study. For one, this was a single-center retrospective analysis, highlighting the need for future large-scale multi-center prospective analyses or controlled trials in order to more rigorously assess the value of CDVs as accesses when treating LEDVT. In addition, this study only assessed perioperative outcomes, while mid- and long-term results were not analyzed.