The patient was taken to the operating room, and he layed in a prone position. The left popliteal vein was accessed percutaneously by 7F sheath via Seldinger technique under local anesthesia. An ultrasound was used to facilitate the percutaneous access. A 0.035-inch hydrophilic guide wire (Terumo Corporation, Shibuya-ku, Tokyo, Japan) was progressed to the inferior vena cava through the thrombotic segment. The infusion delivery catheter was advanced over the wire until the tip of the catheter passed through the thrombotic section. The guide wire was removed and the microsonic ultrasound core containing multiple ultrasound transducers was inserted into the delivery catheter. The infusion of the lytic drug (Actilyze) started in the ultrasonic core. The whole process was overseen using the C-armed fluoroscopy.

After the implantation of the ultrasound-enhanced catheter, he was taken to the in-patient ward where he spent the next 24 hours in the EKOS EndoWave System operation. However, after 10 hours of the ultrasoundenhanced catheter-directed thrombolysis process, he started to feel a burning and piercing pain in his left lower abdominal wall. On anamnesis, he described a sudden involuntary movement of hyperflexion of the left thigh while asleep during the night. On physical examination, his lower left abdomen was tender, and he was feeling increased pain during external compression. The ultrasonic catheter was immediately stopped, and a computed tomography (CT) scan was performed to visualize the course and the tip of the catheter. The course of the catheter was normal until the external iliac vein (Figure 1). However, the anteroposterior plain X-ray and CT views revealed that the catheter had ripped during its route perforating the iliac vein and had advanced into the rectus abdominalis muscle (Figure 2). The transverse slices of the CT showed that the extravasation point was somewhere at the external iliac vein level (Figure 3). The EKOS EndoWave catheter system was entirely withdrawn and removed. The patient's abdominal pain instantly faded away.

Figure 1: Computed tomography angiography scans showing the upward course of the EKOS EndoWave catheter from the popliteal vein to the common femoral vein. Note the subcutaneous changes of the left leg caused by the edema.

Figure 2: Plain anteroposterior roentgenogram showing the course of the EKOS EndoWave catheter. (a) Note the upper arrow that points to the extravasated tip of the catheter. (b) The computed tomography is showing a segment of the EKOS EndoWave catheter inside the iliac vein.

Figure 3: Consecutive slices of the computed tomography angiography showing the course of the EKOS EndoWave catheter during the extravasation from the iliac vein. Note the arrows are pointing at the iliac vein. The circles are showing the route the catheter tip took while passing out of the iliac vein into the abdominal wall.

The abdominal examination was repeated with frequent intervals so as not to miss an intraabdominal bleed. The patient's total blood count was monitored for the detection of blood loss through the perforated iliac vein wall. Fortunately, no physical or hemodynamic changes implicating an active hemorrhage were observed. The patient was mobilized 12 hours later with no tenderness or hematoma on his abdominal wall.

Since the ultrasonic treatment was left undone, an intravenous (unfractionated heparin 15 IU/kg/h) and oral (calcium dobesilate and warfarin) medication was continued for 10 days until a regression of the symptoms was observed. After the recession of symptoms, the patient was discharged with a scheduled future follow-up. Oral warfarin (5 mg/day) was prescribed to keep the international normalized ratio (INR) between 2.0 to 2.5.

Different treatment modalities have been used in patients with massive DVT or PE, including the systemic anticoagulation, surgical embolectomy, catheter directed thrombolysis, and percutaneous mechanical thrombectomy.[6] Prior to the invention of catheter-based interventional techniques, anticoagulation was the only therapeutic modality used in massive DVT. However, anticoagulation has no direct thrombolytic effect.[7] As a result, anticoagulation-based DVT treatments often do not restore the venous patency, causing permanent damage to the venous valves.[5] In addition, eventual venous stenoses are predisposed to recurrent thrombosis and may cause May-Thurner syndrome if left untreated.[4] The combination of venous obstruction and venous reflux significantly increases the risk of PTS. However, catheter-directed mechanical thrombolysis can remove the thrombus and restore the venous patency and may prevent a recurrent thrombosis, PE or PTS.[6]

The EKOS EndoWave Infusion Catheter System (EKOS Corporation, Bothell, WA) is a catheter directed thrombolysis in which the fibrinolytic process acceleration is done via ultrasound waves. The EndoWave System, produced by EKOS Corporation, consists of a 5.2 F, 106-cm-long infusion catheter, an ultrasound treatment core catheter, and a control unit with the interface cables. A series of laser-cut microinfusion pores are located along the external infusion catheter for the delivery of the thrombolytic drug. The core catheter consists of microsonic transducer elements (2 MHz, 0.45 W) that were distributed evenly 1.0 cm apart from each other along its leading tip. They deliver the ultrasound energy radially along the coaxial infusion zone. The microinfusion pores are positioned to optimize the interaction with the corresponding ultrasound transducers. This improves the efficiency of the thrombolytic process and it decreases the treatment time and the administered lytic dose. Moreover, the overall expense and the risk of associated complications such as bleeding are reduced.[8]

This extravasation of the catheter by perforating the iliac vein was the first such complication of the EKOS EndoWave system encountered thus far and no similar case was found in the recent literature. The probable mechanism is thought to be mechanical. A sudden flexor movement of the thigh might have conducted a direct force to the catheter. This axial force might have caused a forward displacement of the whole catheter. As a result, the bare tip of the catheter displaced and ripped the iliac vein and went outside through the abdominal muscles.

As a conclusion, EKOS EndoWave catheters should always be secured to avoid sudden movements of the implanted limb. Elevation of the leg or the body should be restricted to a particular angle that does not disturb the alignment of the catheter inside the vein. If movement of the patient becomes inevitable, the system should be temporarily shut down. If an iliac vein injury occurs during the catheter-based thrombolysis, the catheter should be withdrawn immediately, and the administration of anticoagulant or thrombolytic agents should be stopped as soon as possible. The patient's blood count should be monitored, and an abdominal examination should be repeated at short intervals during the first 24 hours.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

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