Increasing stent system for TIPS : in vitro study

经颈静脉肝内门静脉系统分流术（TIPS）是肝硬化合并门静脉高压性肠胃病、顽固性静脉曲张或大量腹水的有效门静脉减压治疗方法。然而，门系统分流术后常出现肝功能衰竭或肝性脑病等并发症。避免不可逆的过分流在TIPS手术中尤为重要，因为在日本大多数肝硬化患者都有肝脏萎缩过程。我们的研究目的是设计一种新的“增加支架系统”，使其能够在TIPS路线上逐步提升门静脉系统分流流。我们使用丝线制作了两种具有狭窄段的捆绑裸支架（Wallstent RP, 10mm x 49mm, Boston Scientific）和覆盖支架（Niti-STMCom Vi stent, 10mm x 5cm, CMI Century Medical）。狭窄的裸支架或覆盖支架通过使用PTA切割球囊导管切割捆扎缝合线有意地进行扩张（Boston Scientific）。体外磁共振研究的流动动力学使用手工血管幻影然后进行。在二维电影相衬MRI上进行流量测量。MRI参数设置如下；TR/TE/NEX=29/5/1， FA=33度，带宽=31.25kHz， FOV=10 × 10cm, Matrix=128 × 128，切片厚度=4mm， VENC=60cm/s，成像时间=1min20sec。这些研究表明，改良狭窄覆盖支架放置时血流速度和血流体积明显降低，而改良狭窄裸支架放置时血流无明显变化。从这些体外研究中建议制造所谓的“增加支架系统”。在TIPS手术中应用“增加支架系统”之前，建议进行进一步的体内动物研究。

Transjugular intrahepatic portosystemic shunt (TIPS) is an effective portal decompression therapy for the cirrhotic patient with portal hypertensive gastroenteropathy, intractable varix or massive ascites. However, portosystemic overshunting often brought troublesome complication of hepatic failure or hepatic encephalopathy after the TIPS making. To avoid the irreversible overshunting is especially essential in TIPS procedure because most patients with hepatic cirrhosis have atrophic process of the liver in Japan. The aim of our study is to make a newly designed "increasing stent system" which is able to elevate portosystemic shunt flow gradually in the TIPS route. Using a silk suture, we made two kinds of tied bare (Wallstent RP, 10mm x 49mm, Boston Scientific) and covered stent (Niti-STMCom Vi Stent, 10mm x 5cm, CMI Century Medical) having stenotic segment(s). The stenotic bare or covered stent was intentionally able to dilate by means of cutting the tied suture using a PTA cutting balloon catheter (Boston Scientific). In vitro MR studies on flow dynamics using a handmade vascular phantom was then carried out. Flow measurement was made in 2D cine phase contrast MRI. MRI parameters were set as follows ; TR/TE/NEX=29/5/1, FA=33 degrees, Band width=31.25kHz, FOV=10 x 10cm, Matrix=128 x 128, Slice thickness=4mm, VENC=60cm/s, imaging time=1min20sec. These studies demonstrated marked decrease of flow velocity and flow volume at the placement of modified stenotic covered stent, and no remarkable flow change at the deployment of modified stenotic bare stent. Making a so called "increasing stent system"was suggested from these in vitro studies. Further in vivo animal studies would be recommended before the clinical application of the "increasing stent system" in TIPS procedure.