Early arteriovenous fistula after radiofrequency ablation of long saphenous vein

History

A 75-year-old woman presented with symptomatic varicose veins with complaints of ache and itching in her legs. She had previously had left distal calf varicosity treated by liquid sclerotherapy 30 years ago. On examination she had symptomatic moderate-sized varicosities on both legs with no evidence of venous skin changes. Duplex scan showed incompetent left long saphenous vein (LSV) refluxing from a significantly incompetent left saphenofemoral junction (SFJ). In June 2009 the patient underwent radiofrequency ablation (RFA) (VNUS Closure Fast: Covidien^®) of left LSV. Standard procedure for RFA was used with injection of 500 mL of tumescent anaesthesia along the LSV and treatment at 120°C for 20 seconds with double treatment near SFJ and single treatments along the rest of LSV up to knee level.

Postprocedure duplex scan five months later (November 2009) detected high-velocity low-resistance arterial flow into the very proximal thigh LSV ‘stump’ indicative of an arteriovenous fistula (AVF). This appeared to be associated with a small artery in the groin that traced to the common femoral artery (CFA). Arterialized flow was also noted in the common femoral vein (CFV) at the level of SFJ. The thigh LSV was satisfactorily occluded from 2 cm below the SFJ. An angiogram was performed (in March 2010) which revealed communication between a proximal branch of left CFA and left CFV (Fig. 1). Coil embolization of persistent AVF was undertaken in September 2010, by placing two 3 mm × 3 cm coils in the communicating branch of left CFA (Fig. 2). Postcoiling there was no flow in the CFV with the tip of the second coil protruding into the superficial femoral artery (SFA), which remained patent. Although coil embolization appeared to be successful on completion angiography, a follow-up duplex scan in October 2010 showed a patent SFA and persistence of AVF. Although the patient remained asymptomatic, as the AVF was between the major vessels of the limb spontaneous regression was not expected. Also the presence of the embolization coil protruding in SFA remained a cause of concern. Decision was therefore made for operative repair of AVF and removal of coil. This was undertaken successfully in November 2010 (Fig. 3). The patient made an uneventful recovery with a postoperative duplex scan confirming the absence of AVF.

OPEN IN VIEWER

Figure 1

Contrast in common femoral artery (CFA) is seen passing into the common femoral vein via a small branch of CFA (arrow)

OPEN IN VIEWER

Figure 2

Embolization coil (arrow) placed in the branch of common femoral artery leading into the arteriovenous fistula. No contrast in common femoral vein suggesting a successful treatment. Tip of the coil can be seen protruding into superficial femoral artery

OPEN IN VIEWER

Figure 3

Prolene ligation of fistula site on common femoral artery (black arrow) and stub of the ligated saphenofemoral junction (white arrow)

Discussion

AVF occurring after endovenous treatment of varicose veins remains a rare complication with only three cases reported in two publications after RFA.^1,2

Hypotheses regarding the formation of AVF after endovenous ablation include administration of insufficient tumescent anaesthesia leading to increased heat transfer, microperforation and formation of an AVE. ³ Formation of small vessel network due to post-RFA inflammation is another postulated hypothesis of causation. ⁴ The presence of neovascularization after intraluminal thrombosis post-RFA has also been suggested for promoting an AVF post-RFA. ⁵ However, proof for any of these hypotheses is still inconclusive. Also the rapid occurrence of AVF after RFA may suggest direct injury rather than evolution of neovascularization postinflammation and thrombosis.

Poor cutaneous wound healing in older patients ⁶ may reflect in poor vascular healing. Age range of patients (including our case) reported to have an AV fistula post-RFA is between 59 and 75 years. Therefore we speculate that old age of patients may also be a contributing factor in the formation of post-RFA AVF.

Detection of AVF following RFA may be difficult as patients are often not symptomatic and the early postprocedure duplex ultrasound may not pick initial small AVF. In all the previously reported cases of AVFs following RFA the earliest detection was at one year following the procedure. ² In our case we were able to detect the AVF on first postprocedure scan that was performed after four months of RFA, which is in line with our current follow-up policy.

Duplex ultrasound remains the most common modality used for initial detection. Additional imaging tools include computed tomography, magnetic resonance and arteriography.^1,2 In our case difficulty in establishing the communications of a suspected AVF on initial duplex scan lead to the use of arteriography.

Treatment options vary and may include a conservative approach ² or interventions including coil embolization. ¹ Although our patient was asymptomatic and conservative approach could have been persisted with, we did not expect this AVF between CFA and a branch of the CFV to resolve on its own because it was proximal and fed into the major venous outflow of the leg. As it was an early occurrence of AVF post-RFA and the fistula had not occluded spontaneously, after six months of its confirmation on angiogram, we deemed it necessary to intervene. Coil embolization was unsuccessful and surgical intervention was undertaken also due to the fact that one of the embolization coils was protruding into the SFA. Although this was not impeding blood flow in SFA, in our opinion it was unsafe to leave the coil as it would have been a potential nidus for thrombosis. To our knowledge this is the first case of early AVF post-RFA where surgical intervention was required for treatment. Interesting points raised by this case are the occurrence of an early and proximal AVF. Although standard treatment with tumescent anaesthesia and regulated heat intensity was used the occurrence of AVF was away from the site of most proximal treatment and on a deeper plane. Due to this we contemplate there may have been propagated heat injury despite adequate tumescence.

With the increasing use of RFA for treating incompetent LSVs awareness of this uncommon complication, its diagnosis and treatment options is important.