Allan W. Tulloch

Laparoscopic versus open celiac ganglionectomy in patients with median arcuate ligament syndrome

OBJECTIVE Median arcuate ligament syndrome (MALS) is a rare disorder characterized by abdominal pain and compression of the celiac artery. Traditional management consists of open MAL division, with or without arterial reconstruction. We present our outcomes using a laparoscopic approach and compare them to patients treated with open MAL division during the same period. METHODS A retrospective medical records review of all patients with MALS treated at the University of California-Los Angeles from January 1999 to 2009 was performed. RESULTS Fourteen patients with MALS were treated. All patients underwent an extensive preoperative gastrointestinal (GI) workup with 10 undergoing attempted laparoscopic division of the MAL and celiac ganglion (laparoscopic ganglionectomy [LG]). Two intraoperative conversions were performed for bleeding. Six patients were treated in the open surgery group (open ganglionectomy [OG]). There were no deaths or reoperations in either group. Median time to feeding was 1.0 vs 2.8 days (P≤.05) in the LG and OG groups, respectively, which was statistically significant. Median length of hospitalization was also significantly lower in the LG group compared with the OG group (2.3 vs 7.0 days; P≤.05). Eight patients had LG (100%) and 5 patients had OG (83%) and had immediate symptom resolution (postoperative day 1). Three patients with recurrent symptoms after LG underwent angiography demonstrating persistent celiac stenosis, then an angioplasty was performed. Median follow-up was 14.0 months (2-65 months) for all patients. Three patients who received LG (38%) and 3 patients who received OG (50%) had persistent pain at last follow-up. Six patients in the OG group (100%) and 7 patients in the LG group (88%) had ceased taking chronic oral narcotics at their last follow-up visit. CONCLUSION Both laparoscopic and open MAL division and celiac ganglionectomy can be safely performed with minimal patient morbidity and mortality. Late recurrence is frequently seen; however, this seems to be milder than the presenting symptoms. The laparoscopic approach results in avoidance of laparotomy and was associated with shorter inpatient hospitalization and decreased time to feeding in our study. Optimal patient selection and prediction of clinical response in these patients remains a challenge.

Thin-film nitinol (NiTi): A feasibility study for a novel aortic stent graft material

OBJECTIVE Although technological improvements continue to advance the designs of aortic stent grafts, miniaturization of the required delivery systems would allow their application to be available to a wider range of patients and potentially decrease the access difficulties that are encountered. We performed this feasibility study to determine if thin-film NiTi (Nitinol) could be used as a covering for stent grafts ranging from 16 mm to 40 mm in diameter. Specifically, we wished to determine the profile reduction attainable and improve the flexibility of our design. METHODS Using a novel hot-sputter deposition technique, we created sheets of thin-film NiTi (TFN) with a tensile strength of >500 Megapascal (MPa) and thickness of 5-10 microns. TFN was used to cover stents, which were then deployed in vitro. Patterned thin film was fabricated via a lift-off technique; grafts were constructed with stents ranging from 16-40 mm and deployed in a pulsatile flow system from the smallest diameter polymer tubing into which the stent and TFN would fit. The bending/stiffness ratio vs similar sized expanded polytetrafluoroethylene (ePTFE)-covered stents was also determined. RESULTS TFN was created in both non-patterned and patterned forms, with a tensile strength of >100 MPa for the latter. We created devices that were successfully deployed via delivery systems half the size of fabric-covered stent grafts (ie, the 16 mm stent graft that originally was delivered via a 16French (F) system was reduced to 8F, and the 40 mm stent graft delivered via a 24F system was reduced to 12F). No migration of the devices was observed with deployment in both straight and curved tubing, which was sized so that the stent grafts were oversized by 20%. Both forms of the thin-film were noted to be more flexible than the same sized ePTFE stent graft, and the patterned graft had an additional 15-30% flexibility vs the non-patterned film. CONCLUSION These in vitro results demonstrate the feasibility of TFN for covering stent grafts designed for placement in the aorta. The delivery profile can be significantly reduced across a wide range of sizes, while the material remained more flexible than ePTFE.

Super Hydrophilic Thin Film Nitinol Demonstrates Reduced Platelet Adhesion Compared with Commercially Available Endograft Materials

BACKGROUND Thin film nitinol (TFN) is a novel material with which to cover stents for the treatment of a wide range of vascular disease processes. This study aimed to show that TFN, if treated to produce a super hydrophilic surface, significantly reduces platelet adhesion, potentially rendering covered stents more resistant to thrombosis compared to commercially available materials. MATERIALS AND METHODS TFN was fabricated using a sputter deposition process to produce a 5-μ thin film of uniform thickness. TFN then underwent a surface treatment process to create a super hydrophilic layer. Platelet adhesion studies compared surface treated TFN (S-TFN) to untreated TFN, polytetrafluoroethylene, Dacron, and bulk nitinol. In vivo swine studies examined the placement of an S-TFN covered stent in a 3.5 mm diameter external iliac artery. Angiography confirmed placement, and repeat angiography was performed at 2 wk followed by post mortem histopathology. RESULTS S-TFN significantly reduced platelet adhesion without any evidence of aggregation compared with all materials studied (P < 0.05). Furthermore, in vivo swine studies demonstrated complete patency of the S-TFN covered stent at 2 wk. Post mortem histopathology showed rapid endothelialization of the S-TFN without excessive neointimal hyperplasia. CONCLUSIONS These results demonstrate that S-TFN significantly reduces platelet adhesion and aggregation compared with commercially available endograft materials. Furthermore, the hydrophilic surface may confer thromboresistance in vivo, suggesting that S-TFN is a possible superior material for covering stents.

In vitro hemocompatibility of thin film nitinol in stenotic flow conditions.

Because of its low profile and biologically inert behavior, thin film nitinol (TFN) is ideally suited for use in construction of endovascular devices. We have developed a surface treatment for TFN designed to minimize platelet adhesion by creating a superhydrophilic surface. The hemocompatibility of expanded polytetrafluorethylene (ePTFE), untreated thin film nitinol (UTFN), and a surface treated superhydrophilic thin film nitinol (STFN) was compared using an in vitro circulation model with whole blood under flow conditions simulating a moderate arterial stenosis. Scanning electron microscopy analysis showed increased thrombus on ePTFE as compared to UTFN or STFN. Total blood product deposition was 6.3 ± 0.8 mg/cm(2) for ePTFE, 4.5 ± 2.3 mg/cm(2) for UTFN, and 2.9 ± 0.4 mg/cm(2) for STFN (n = 12, p < 0.01). ELISA assay for fibrin showed 326 ± 42 μg/cm(2) for ePTFE, 45.6 ± 7.4 μg/cm(2) for UTFN, and 194 ± 25 μg/cm(2) for STFN (n = 12, p < 0.01). Platelet deposition measured by fluorescent intensity was 79,000 20,000 AU/mm(2) for ePTFE, 810 ± 190 AU/mm(2) for UTFN, and 1600 ± 25 AU/mm(2) for STFN (n = 10, p < 0.01). Mass spectrometry demonstrated a larger number of proteins on ePTFE as compared to either thin film. UTFN and STFN appear to attract significantly less thrombus than ePTFE. Given TFNs low profile and our previously demonstrated ability to place TFN covered stents in vivo, it is an excellent candidate for use in next-generation endovascular stents grafts.

Computational Modeling and Experimental Characterization of Hyperelastic Thin Film NiTi for Neurovascular Microstent Applications

A novel hyperelastic thin film NiTi covered neurovascular microstent was developed for treating wide-neck and fusiform neurovascular aneurysms. This device requires 300–500% recoverable elongation for both collapsing and deployment. Nonlinear buckling and static analysis of Finite Element Modeling (FEM: ANSYS software used) was applied for obtaining critical buckling stress and critical strain values depending on thickness, strut width and pore height. A maximum theoretical critical strain for one geometry as high as 316% while a different experimentally tested film was found to strain 600% elastically without any signs of permanent deformation.Copyright