Interventional research is one of the three main missions of the Dotter Department.
The Department's faculty members have been active in both laboratory and clinical interventional research. They also participate in projects of researchers from other OHSU departments and from other institutions both in the USA and abroad.
Both laboratory and clinical research has been directed toward improving existing tools and developing and testing new techniques of interventional therapy.
Much of this research has been done in cooperation with several medical device companies, primarily Cook Medical, Bloomington, IN. Participation in national randomized prospective clinical trials has been an important component of the Department's clinical research.
Clinical research: innovations and outcomes
Clinical research has occurred in parallel with research done in the Department's laboratory. In the early 1990s, research areas included evaluation of effectiveness of self-expandable GRZ stents in treatment of obstructions of the venous system, tracheobronchial tree and esophagus. We also carried out detailed investigation of many aspects of the TIPS procedure.
We found GRZ stents to be very effective in long-term treatment of benign stenoses in the venous system. Covered GRZ stents were excellent in palliating malignant esophageal obstructions. In exploring TIPS, the Department's faculty has been working closely with liver transplant and hepatology teams. Based on experience with treatment and close follow-up of treated patients, the benefits and limitations of TIPS have been well defined. The Department's clinical study showed that PTFE stent grafts had significant potential to prevent shunt obstructions, previously, a major limitation of TIPS. Our research demonstrated these stent grafts have been effective, not only in treatment of shunt obstructions, but also for primary TIPS procedures.
Presently, we have done TIPS in more than 1,000 patients. The DIPS procedure, a TIPS modification, developed by Dr. Bryan Petersen with our research laboratory and was successfully performed in more than 150 patients. The DIPS procedure is now performed world-wide.
In the late 1990s, we introduced embolization of uterine fibroids to our clinical practice. Uterine fibroid embolization is effective in treating large, symptomatic uterine fibroids. It is a benign procedure and is usually done on an outpatient basis. As an alternative to surgical hysterectomy, many women have requested it. Outcomes of our more than 200 patients have been excellent, with fibroid volume reductions of 40-60 percent and symptoms either resolved or significantly improved in 80 percent.
We also expanded the number of patients seen for embolization of pulmonary arteriovenous malformations. To treat patients with pulmonary AVMs more effectively, OHSU has become one of 9 HHT centers in North America. We treat patients from the Pacific Northwest and other regions of the western USA.
Since 2000, the Department's clinical research expanded into evaluation of endovascular treatment of aneurysms, venous insufficiency, IVC filters and oncologic interventions, particularly treatment of primary and secondary liver tumors.
Endovascular treatment of aneurysms is performed in cooperation with vascular surgeons. In treating AAA, endografting is very effective with significant decreases in patient length of stay.
The Department's team was also the first in the Northwest to implant an aneurysm pressure sensor for follow-up of patients with endovascular treatment. Successful treatment of venous insufficiency with venous ablation using either laser or radiofrequency is performed on an outpatient basis. Several optional IVC filters were evaluated for their safety and retrievability and occurrence of pulmonary embolism after retrieval.
Evaluation of interventional oncological treatment is being done in close cooperation with hepatologists, surgical oncologists and urologists. Several types of chemo and radio-embolization and radiofrequency and cryoablation are being explored in treatment of liver and kidney tumors.
The Department's faculty has been actively involved with several national studies, some of them supported by NIH. These include:
- Transarterial chemoembolization for hepatic malignancy
- Clinical follow-up after retrieval of IVC filters
- Outcome of TIPS
- Outcome of uterine artery embolization for leiyomyomas
- Evaluation of the access sites after use of arterial closure devices and correlation of portal vein diameter and hepatic vein pressures
Presently, the Department's staff are enrolling patients for several studies that will explore endovascular treatment of thoracic aortic aneurysms, thrombus removal in acute venous thrombosis, new embolization material for treatment of hepatocellular carcinoma and comparison of exercise vs. endovascular treatment for peripheral revascularization.