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Laboratory Research
   First Decade
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   Dr. Pavcnik
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   Dr. Barnwell
Clinical Research

Dotter Interventional Institute

IR Laboratory Research - First Decade

Laboratory research in the Institute has been focused mainly on developing and testing new tools and techniques for interventional radiology. In the early nineties, we investigated modified self-expandable Gianturco-Rösch Z stents for use in treatment of venous, tracheobronchial, esophageal and biliary obstructions. After the Institute’s successful development of these devices, they became widely used in clinical practice. The Institute also designed a transjugular liver biopsy set. It has become the worldwide standard needle for this procedure. The needle from this set was subsequently modified with a side-cut opening and a blunt-tipped stylet making it more efficient and safe for transjugular renal biopsies. A sheath for introducing large diameter stentgrafts also found wide use in clinical practice.

Experimental TIPS created with home made PTFE graft supported by a Wallstent (1993) A) The device (B) X-ray of the placed device C) Good TIPS patency at 3 months D) Specimen

In the mid-nineties, the Institute’s research team concentrated on developing covered stents and stent grafts for arterial, venous, TIPS and nonvascular uses. A twin tube endograft was initially promising for excluding abdominal aortic aneurysm. Once the cause of TIPS track occlusion was determined to be leakage of thrombogenic bile and mucin into the shunt track created with bare metal stents, we experimented with various types of covered stents to prevent thrombogenic substances from entering the TIPS track. Silicon, polyethelene and polyurethane were not satisfactory for this purpose. However, PTFE covered stents had long-term patency when used for TIPS. Based on this, we developed a PTFE graft supported by a Wallstent with a Z stent at the portal vein end. Once this device was shown to stay patent in experimental studies, we did clinical experiments with both thrombosed and de-novo TIPS in patients.

Direct transjugular portocaval shunt done under intravenous ultrasound and flouroscopic control

Two new techniques for treatment of portal hypertension were also developed and tested. In the first technique-direct intrahepatic portacaval shunt (DIPS), the portal vein is accessed directly from the inferior vena cava with intravenous ultrasound guidance. DIPS became an alternative for conventional TIPS in special situations. The second technique – percutaneous retroperitoneal splenorenal shunt was interesting, but so far has not been applied clinically.

In the late-nineties, Dr. Pavcnik created a new, exciting stent – the square stent. This stent has potential as a platform for other devices such as the venous valves and IVC square stent filter.

Another laboratory study was to determine of the safety of intravascular thrombin for pseudo aneurysm occlusion. The Institute’s research results indicated that minimal thrombin doses can be used without risks of severe complications.

Collaborative work with visiting researchers led to development new tools and techniques. Dr. Stan Cope’s (from the University of Pennsylvania) research resulted in the technique of percutaneous transabdominal thoracic duct catheterization and occlusion. Working with Dr. Michael Conlin, OHSU urologist, we developed new devices for the urinary tract. The Institute has also been collaborating with Dr. Kent Gregory from Oregon Medical Laser Center on several topics including laser treatment of arterial intimal hyperplasia and use of a new collagen biomaterial – elastin stent cover – for prevention of arterial stenoses complicating coronary stenting.