Hans A. Timmermans

Percutaneous transcatheter aortic disc valve prosthesis implantation: A feasibility study

AbstractPurpose: Over the past 30 years there have been experimental efforts at catheter-based management of aortic valve regurgitation with the idea of extending treatment to nonsurgical candidates. A new catheter-based aortic valve design is described. Methods: The new catheter-delivered valve consists of a stent-based valve cage with locking mechanism and a prosthetic flexible tilting valve disc. The valve cage is delivered first followed by deployment and locking of the disc. In acute experiments, valve implantation was done in four dogs. Results: Valve implantation was successful in all four animals. The implanted valve functioned well for the duration of the experiments (up to 3 hr). Conclusion: The study showed the implantation feasibility and short-term function of the tested catheter-based aortic disc valve. Further experimental studies are warranted.

Stent-Grafts for Revision of TIPS Stenoses and Occlusions: A Clinical Pilot Study

PURPOSE To assess the clinical and technical results of stent-graft placement for revision of transjugular intrahepatic portosystemic shunt (TIPS) stenoses and occlusions. MATERIALS AND METHODS Six patients who developed recurrent TIPS stenosis or occlusion of the parenchymal tract underwent shunt revision with use of polytetrafluoroethylene (PTFE) stent-grafts anchored at both ends by Z stents and centrally supported by Wallstents. RESULTS Before graft placement, mean primary patency was 50 days (range, 9-100 days). Patients underwent one to eight revisions with angioplasty or stent placement (mean, 3.2). Three patients had biliary-TIPS fistulas documented with use of a prototype double occlusion balloon catheter. Stent-grafts were successfully placed within the obstructed shunt, creating an excellent lumen in all cases. The portosystemic gradient was decreased from a mean of 24.3 mm Hg (range, 12-35 mm Hg) to a mean of 10.3 mm Hg (range, 7-16 mm Hg). Five of six patients were asymptomatic and no complications occurred (median clinical follow-up, 331 days). One patient died of pre-existing multi-organ system failure. The duration of primary patency after stent-grafting was improved (mean, 229 days; range, 27-324 days) and the difference approached statistical significance despite the small sample size (P = .056, paired t test). Three patients remained primarily patent at a mean venographic follow-up of 315 days. One shunt occluded at 1 month from residual thrombus in the portal vein, and one stenosis occurred that was secondary to misplacement of the original stent-graft. Patency was re-established in each of these patients. CONCLUSION PTFE covered stent-grafts are effective for shunt revision in patients with tract stenosis or occlusion and appear to improve TIPS patency.

Aortic and venous valve for percutaneous insertion

Summary The purpose of this paper is to present in vitro and in vivo experimental evaluation of a new, artificial, bicuspid, aortic and venous valve. Valves were constructed from square stents with barbs covered by porcine small intestine submucosa (SIS). A valve 15 mm in diameter was tested in a flow model (2.5 l/min) with pressure measurement. A 100-ml rubber bag attached to a side arm of the flow model simulated heart ejection fraction. In acute (n=6) and short-term (n=3) experiments conducted in four swine and four dogs, valves ranging from 16 - 28mm in diameter were placed into the ascending aorta through 10 F sheaths; three were placed subcoronary and six in a supracoronary position. Function and stability of the valves were studied with pressure measurements and aortograms. Three short-term animals were sacrificed for gross and histologic evaluation at one, two and four weeks respectively. In an acute experiment, venous valves with four barbs were placed into the IVC through an 8 F guiding catheter in three dogs. For longer-term testing, valves were placed into the IVCs and iliac veins of three young swine. The animals were followed up after two weeks with venograms, then were sacrificed for gross and histologic evaluation.

Treatment of Malignant Esophageal Obstructions with Covered Metallic Z Stents: Long-term Results in 52 Patients☆

PURPOSE To prospectively evaluate the clinical efficacy of silicone-covered Gianturco-Rösch self-expandable Z (GRZ) stents in the treatment of malignant esophageal obstruction. PATIENTS AND METHODS GRZ stents were placed in 52 patients (39 men, 13 women) with severe dysphagia due to high-grade malignant esophageal obstruction. RESULTS Stent placement was technically successful, and immediate relief of dysphagia was achieved in 50 of 52 patients (96%), with long-term relief in 47 patients (90%). Fifty-one patients (98%) died during follow-up (range, 1 week to 33 months; mean, 4.3 months). Late complications were most prevalent and included stent migration (n = 5), food impaction (n = 2), chest pain (n = 2), membrane disruption with tumor ingrowth (n = 1), granulomatous reaction above the stent (n = 1), esophageal perforation with mediastinitis (n = 1), and upper gastrointestinal hemorrhage (n = 4). Twelve complications were easily managed with medical, endoscopic, or radiologic intervention. Four deaths may have been related to stent placement (early mortality rate, 7.7%). CONCLUSION GRZ stents provide relatively safe and effective long-term palliation in patients with severe, malignant esophageal obstruction.

Treatment of Malignant Esophagorespiratory Fistulas with Silicone-covered Metallic Z Stents

PURPOSE To prospectively evaluate the clinical efficacy of covered metallic Z stents in the treatment of esophagorespiratory fistulas (ERFs). PATIENTS AND METHODS Twelve patients with severe aspiration symptoms from malignant ERFs were treated with silicone-covered, metallic, self-expanding Gianturco-Rösch Z (GRZ) stents. RESULTS Fluoroscopically guided stent placement was successful and well tolerated in all patients. Immediate postprocedural endoscopy and esophagography showed excellent coverage of the fistulas in all cases. Aspiration symptoms were completely relieved in eight of 12 patients (67%). Four of 12 patients (33%) were improved and able to eat a soft diet. There were no stent-related deaths. Nine patients have died and three patients are alive. Mean follow-up for the entire group was 3.9 months (range, 1 week to 10.5 months). Nonfatal complications occurred in three of 12 patients (25%). Complications included one membrane disruption and one granulomatous reaction with a slight upward stent migration. CONCLUSION GRZ stents are an effective and safe means of palliation in patients with malignant esophagorespiratory fistulas.

Intravascular US-guided direct intrahepatic portacaval shunt with a PTFE-covered stent-graft: feasibility study in swine and initial clinical results.

PURPOSE To determine the feasibility of the creation of a direct intrahepatic inferior vena cava (IVC)-to-portal-vein shunt with puncture guided by a transfemorally placed intravascular ultrasound (IVUS) probe and use of a polytetrafluoroethylene (PTFE)-covered stent-graft. MATERIALS AND METHODS In five swine, transjugular access was used to perform a direct puncture from the IVC to the portal vein with use of a modified Rosch-Uchida Portal Access set directed with real-time IVUS (9 MHz) introduced from a transfemoral venous approach. The direct intrahepatic portocaval shunt (DIPS) was then created with single or overlapping PTFE-covered Palmaz stents placed through a 10-F sheath and dilated to a diameter of 8 mm. Follow-up was performed with transhepatic portography at 2, 4, and 8 weeks. Animals were killed when shunts occluded or at the termination of the study at 8 weeks. Gross and microscopic histologic study was performed on sacrificed animals. A similar technique was used to create DIPS in five patients with intractable ascites, with follow-up by US and venography. RESULTS All experimental DIPS created in swine were created without complications. Portal vein punctures were achieved in four of five swine on the first or second pass of the needle. Follow-up transhepatic portography at 2 weeks demonstrated occlusion of two shunts, both explained by technical reasons at sacrifice. At 4 and 8 weeks, the remaining three shunts were patent on portography. Histology showed a thin neointimal lining with no significant tissue ingrowth or hyperplasia. Clinically, in five patients, successful puncture of the portal vein from the IVC was achieved in one to three passes. Creation of DIPS led to a reduction of mean portosystemic gradient from 18-29 mm Hg (mean, 24 mm Hg) to 9-10 mm Hg (mean, 9 mm Hg). One patient died of liver failure 2 days after creation of DIPS. The other four patients were doing well 2-15 months (mean, 8 months) after the procedure, with patency confirmed by US and venography. CONCLUSION Creation of DIPS is technically feasible, and the direct IVC-to-portal-vein puncture can be done accurately with real-time IVUS guidance. Further studies and longer follow-up are necessary to determine if the short length of the PTFE-covered stent-graft and avoidance of the hepatic vein will increase the long-term patency compared to standard transjugular intrahepatic portosystemic shunt creation.

Stent-graft in the management of superior vena cava syndrome.

We report the use of a Dacron-covered Gianturco-RöschZ (GRZ)-stent to treat malignant obstruction of the superior vena cava (SVC). Initial treatment with an uncovered GRZ-stent was suboptimal due to protrusion of tumor-thrombus through the stent struts into the SVC lumen. Placement of a coaxial Dacron-covered stent graft relieved the residual obstruction due to tumor within the SVC.

Square stent: a new self-expandable endoluminal device and its applications.

The square stent is a new, simply constructed, self-expanding device that has recently been described. Compared with other stents, the square stent has a minimal amount of metal and thus requires a smaller-diameter catheter for introduction. Despite the small amount of metal present, the square stent has adequate expansile force. We have been evaluating the square stent for various interventional applications. In addition to the basic square stent, combinations of square stents and coverings for square stents were developed and evaluated to expand its uses and indications. One of the coverings tested is a new biomaterial: small intestinal submucosa (SIS). This paper will discuss the various applications of the square stent, which include a retrievable inferior vena cava filter, vascular occluder, graft adapter, and venous and aortic valves. In addition, we will review the important properties of SIS as a covering for the square stent.

Treatment of Refractory Benign Biliary Stenoses in Liver Transplant Patients by Placement and Retrieval of a Temporary Stent-Graft: Work in Progress

PURPOSE To evaluate patency of refractory benign biliary strictures in liver transplant patients treated with retrievable stent-grafts. MATERIALS AND METHODS Eight male liver transplant patients who ranged in age from 42 to 52 years developed nine symptomatic biliary strictures (intrahepatic left duct, 1; hilar, 2; anastomotic, 6). These strictures had recurred despite multiple previous attempts of treatment (n = 33), including angioplasty (n = 27), surgery (n = 1), atherectomy (n = 1), metallic stent (n = 1), and prolonged catheter drainage (n = 3). As an alternative method of treatment for these refractory biliary strictures, transhepatic placement of expanded polytetrafluoroethylene stent-grafts across the strictures was performed through 10-F sheaths. In total, 14 stent-grafts were placed to treat the nine lesions, and nine of these stent-grafts were subsequently retrieved through 12-16-F sheaths. RESULTS Stent-grafts were deployed successfully. Delayed migrations in two patients required additional stent-graft placement. One patient died of pneumonia 1 month after stent-graft placement; the remaining seven patients had stent-grafts successfully removed at 3-10 months (mean, 5.6 months). Nine intended stent-graft retrievals were performed successfully, with two requiring use of elongated forceps. Immediately after treatment, all strictures were widely patent. Five to 6 months after stent-graft removal in these seven patients, significant strictures recurred in four of eight lesions (50%). One patient underwent surgical revision. At 6-29 months (mean, 12 months) after stent-graft removal, the remaining six patients were without clinical or laboratory evidence of biliary obstruction, despite three patients with significant recurrent strictures. CONCLUSION Temporary stent-graft placement for treatment of benign biliary strictures in liver transplant patients is technically feasible. Longer follow-up with larger patient series is necessary to assess effectiveness and possible broader applications.

In Vitro Comparison of the Spiral Z Stent and the Gianturco Z Stent

A new spiral Z stent is described, and its characteristics are compared in vitro with those of the modified Gianturco Z stent. The spiral Z stent has a more uniform expansile force throughout its effective length; is more compressible, thus allowing for use of a smaller introductory catheter; and is more stable than the modified Z stent. Flexibility of both stent types is similar. Advantages of the spiral Z stent promise to be beneficial for clinical use.