Increasing stent system for TIPS : in vitro study

经颈静脉肝内门体分流术（TIPS）是治疗门静脉高压性胃肠病、顽固性静脉曲张或大量腹水的有效方法。但TIPS术后门体分流过度常引起肝衰竭或肝性脑病等严重并发症。在日本，由于大多数肝硬化患者的肝脏都有萎缩过程，因此TIPS手术中避免不可逆的过度分流尤为重要。本研究的目的是设计一种新的“递增式支架系统”，能够在TIPS途径中逐渐提高门体分流流量。使用丝线缝合，我们制作了两种具有狭窄段的打结裸支架（Wallstent RP，10 mm x 49 mm，Boston Scientific）和覆膜支架（Niti-STMCom Vi Stent，10 mm x 5 cm，CMI世纪医疗）。使用PTA切割球囊导管（Boston Scientific）切割打结的缝线，使狭窄裸支架或覆膜支架有意扩张。然后，使用手工制作的血管体模进行体外MR流动动力学研究。在2D电影相位对比MRI中进行流量测量。MRI参数设置如下：TR/TE/NEX=29/5/1，FA=33度，带宽=31.25kHz，FOV=10 x 10 cm，矩阵=128 x 128，层厚= 4 mm，VENC= 60 cm/s，成像时间= 1分20秒。这些研究表明，在放置改良狭窄覆膜支架时，流速和流量明显降低，而在展开改良狭窄裸支架时，流量无明显变化。从这些体外研究中提出了制造所谓的“增加支架系统”的建议。在TIPS手术中应用“递增支架系统”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.