Evaluation of MR/Fluoroscopy–guided Portosystemic Shunt Creation in a Swine Model

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PURPOSE

To evaluate three different percutaneous portosystemic shunts created with magnetic resonance (MR) imaging and fluoroscopy guidance in a swine model.

MATERIALS AND METHODS

In stage 1 of the experiment, an active MR intravascular needle system was created for needle tracking and extracaval punctures. Twenty inferior vena cava (IVC)/superior mesenteric vein (SMV)/portal vein (PV) punctures were performed in 10 swine (weight, 40–45 kg) in a 1.5-T short-bore interventional MR imager. With use of a real-time MR imaging sequence, the needle was guided through the IVC and into the SMV or PV (N= 20 punctures). After confirmation, a wire was advanced into the portal venous system under MR imaging guidance (N = 20). In stage 2, animals were transferred to the radiographic fluoroscopy suite for deployment of shunts. Three different shunts were evaluated in this study: (i) a commercial stent-graft, (ii) a prototype bridging stent, and (iii) a prototype nitinol vascular anastomotic device. Postprocedural necropsy was performed in all animals.

RESULTS

Successful MR-guided IVC/SMV punctures were performed in all 20 procedures (100%). All three shunts were deployed. Stent-grafts had the poorest mechanism for securing a shunt. The vascular anastomotic device and the bridging stent had more secure anchoring mechanisms but also had higher technical failure rates (50% and 40%, respectively). When deployed successfully, the vascular anastomotic device resulted in no bleeding at the sites of punctures at necropsy.

CONCLUSION

Percutaneous shunts and vascular anastomoses between the portal mesenteric venous system and IVC were successfully created with use of a combination of MR imaging and conventional fluoroscopy for guidance.

Section snippets

Animal Model

The institutional animal care and use committee approved the animal studies. We performed experiments on 10 healthy swine (weight, 40–45 kg). Sedation was achieved with xylazine and ketamine. After endotracheal intubation, inhaled isoflurane (2%) was provided during mechanical ventilation with oxygen (98%). Percutaneous access into the right femoral vein was achieved under ultrasound (US) guidance, followed by placement of a 12-F sheath into the femoral vein. All animals were transferred to the

Stage 1: MR-guided Access to Portal-mesenteric Venous System

Successful MR-guided IVC/SMV/PV punctures were performed in all 13 procedures (100%). All procedures were performed with real-time MR imaging sequences with use of freebreathing techniques and without electrocardiographic gating. Punctures were made with no change in cardiac rhythm or rate and with no sequelae. As a result of the mobility of the SMV and PV, real-time imaging was necessary in all punctures to reorient the needle toward the target vessel. During real-time gradient-recalled echo

DISCUSSION

The creation of a percutaneous extrahepatic portosystemic shunt is contingent on two critical steps: (i) safe and dependable extrahepatic transcaval punctures into the portal circulation and (ii) a reliable conduit that will enable shunting into the systemic circulation. We demonstrated that with the use of multiplanar realtime MR imaging and conventional fluoroscopy, a percutaneous extrahepatic portosystemic shunt and an anastomosis can be constructed in a staged fashion. Under complete MR

CONCLUSIONS

Transcaval punctures to the portalmesenteric venous system are feasible with MR imaging guidance. Using a combination of MR imaging and conventional fluoroscopy for guidance, we were able to successfully create a percutaneous shunt and a vascular anastomosis between the portal mesenteric venous system and the IVC.

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This study was supported in part by National Institutes of Health grant 1 K08 EB004348-01, R01 HL61672. None of the authors have identified a conflict of interest.

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