Vascular Access Complications and Clinical Outcomes of Vascular Surgical Repairs Following Transcatheter Aortic Valve Implantation (TAVI).

BACKGROUND: Transcatheter aortic valve implantation (TAVI) procedures have revolutionized the treatment of aortic stenosis. However, due to large sheaths, improperly deployed closure devices, and the comorbidities and challenges innate to this population, vascular access complications can be devastating. The objective of this study is to evaluate vascular access complications in one of the largest TAVI sites in North America. METHODS: This was a retrospective single center review between January 2014 and December 2018 of vascular access complications necessitating operative intervention by vascular surgery. Patient demographics and preoperative comorbidities were collected. Type of vascular access complication, types of repair, closure device used, and postoperative outcomes were analyzed. RESULTS: A total of 37 cases out of a total of 985 TAVI procedures were identified. TAVI was carried out in the operating suite (70%) or the catheterization lab (30%). Consults to vascular surgery were requested intraoperatively (60%), immediately postoperative (14%), later in the day of the TAVI (20%), and on postoperative day 1 (6%). The location of injury included common femoral artery (49%), superficial femoral artery (11%) and external iliac artery (41%), with some cases injuring multiple vessels. Closure devices were found in the subcutaneous tissue (26%), anterior wall (37%), posterior wall (11%), intra-arterial (11%), closing the anterior to the posterior wall (16%), and in the inguinal ligament (5%). Injuries included tears (11%), dissections (38%), and vessel rupture (19%). The majority of repairs were done primarily (64%), with patch (28%) and bypass (8%) less frequently. Four patients died perioperatively (11%), 2 from hemorrhage, 1 from cardiac arrest, and 1 from progressive respiratory disease. CONCLUSIONS: Access complications during TAVI procedures predispose complex patients to increased risk of morbidity and mortality. Careful patient selection, proper access techniques, and performing high risk patients in the operating suite with vascular surgery are fundamental in minimizing complications.

Rail height effects on safety performance of Midwest Guardrail System.

OBJECTIVE: Guardrail heights play a crucial role in the way that errant vehicles interact with roadside barriers. Low rail heights increase the propensity of vehicle rollover and override, whereas excessively tall rails promote underride. Further, rail mounting heights and post embedment depths may be altered by variations in roadside terrain. An increased guardrail height may be desirable to accommodate construction tolerances, soil erosion, frost heave, and future roadway overlays. This study aimed to investigate and identify a maximum safe installation height for the Midwest Guardrail System that would be robust and remain crashworthy before and after pavement overlays. METHODS: A research investigation was performed to evaluate the safety performance of increased mounting heights for the standard 787-mm (31-in.)-tall Midwest Guardrail System (MGS) through crash testing and computer simulation. Two full-scale crash tests with small passenger cars were performed on the MGS with top-rail mounting heights of 864 and 914 mm (34 and 36 in.). Test results were then used to calibrate computer simulation models. RESULTS: In the first test, a small car impacted the MGS with 864-mm (34-in.) rail height at 102 km/h (63.6 mph) and 25.0° and was successfully redirected. In the second test, another small car impacted the MGS with a 914-mm (36-in.) rail height at 103 km/h (64.1 mph) and 25.6° and was successful. Both system heights satisfied the Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) evaluation criteria. Test results were then used to calibrate computer simulation models. A mounting height of 36 in. was determined to be the maximum guardrail height that would safely contain and redirect small car vehicles. Simulations confirmed that taller guardrail heights (i.e., 37 in.) would likely result in small car underride. In addition, simulation results indicated that passenger vehicle models were successfully contained by the 34- and 36-in.-tall MGS installed on approach slopes as steep as 6:1. CONCLUSIONS: A mounting height of 914 mm (36 in.) was determined to be the maximum guardrail height that would safely contain and redirect 1100C vehicles and not allow underride or excessive vehicle snag on support posts. Recommendations were also provided regarding the safety performance of the MGS with increased height.

The development of a material model and wheel-tissue interaction for simulating wheeled surgical robot mobility.

In vivo surgical robot wheel and tissue interaction was studied using a nonlinear finite element model. A liver material model, derived from laboratory experiments, was implemented as a viscoelastic material. A finite element simulation of this laboratory test confirmed the accuracy of the liver material model. This material model was then used as the tissue model to study wheel performance. A helical wheel moving on the liver model was used to replicate laboratory experiments that included several different slip ratios and applied loads. The drawbar force produced in this model showed good agreement with the physical tests. These results have provided the baseline for studying how changes in wheel geometry, such as tread height, tread spacing and wheel diameter, affect drawbar force and ultimately wheel performance. These results will be used in future surgical robot wheel designs.

Successful ventricular transapical thoracic endovascular graft deployment in a pig model.

PURPOSE: Aortoiliac occlusive disease may preclude retrograde thoracic endovascular aortic repair. This study evaluated the physiologic and anatomic feasibility of introducing an aortic endograft in an antegrade manner into the descending thoracic aorta of a pig through the left ventricular apex. METHODS: Twelve adult pigs were to undergo antegrade endograft deployment. Under fluoroscopic guidance, a stiff guidewire was introduced past the aortic valve and into the distal abdominal aorta through the left ventricular apex on a beating heart. An 18F introducer sheath containing a 24 x 36-mm aortic endograft was introduced and deployed in the descending thoracic aorta. The accuracy of graft delivery was determined at necropsy by measuring the distance from the trailing edge of the graft to the downstream margin of the ostium of the left subclavian artery. Aortic valve competency was assessed angiographically and at necropsy. Left ventricular function was assessed angiographically. Five hemodynamic and respiratory variables were recorded at 12 stages during the procedure and assessed for significant changes from baseline. RESULTS: One animal died during the sternotomy. All remaining pigs survived the experiment with minimal hemodynamic support. A significant drop in systolic blood pressure (75 +/- 2 to 60 +/- 4 mm Hg, P = .05) was noted when the aortic valve was crossed with an 18F sheath. The systolic blood pressure returned to baseline on endograft deployment and at the end of the procedure. Bradycardia was noted at several stages of the procedure, requiring treatment in two pigs. Eleven endografts were deployed; seven grafts were delivered within 5 mm and three grafts within 10 to 20 mm of the intended landing point. One graft was deployed 10 mm too proximally, covering the left subclavian artery. No aortic valvular insufficiency or left ventricular dysfunction was noted. CONCLUSION: An aortic endograft can be delivered in an antegrade manner transapically into the descending thoracic aorta in a pig model with a reasonable degree of accuracy and minimal hemodynamic compromise.

Reconstruction techniques for energy-absorbing guardrail end terminals.

Steel beam longitudinal barriers protect errant vehicles from roadside hazards; when impacted, they safely redirect the impacting vehicle and minimize the probability of serious injury. Guardrail end terminals are devices placed on the ends of longitudinal barriers and are frequently hit by vehicles that leave the roadway. Crash reconstruction is the effort to determine how a vehicle crash has occurred. Reconstruction is performed by several groups, including designers and testers of roadside safety devices so that they design and test for real-world conditions, and also by departments of transportation in order to determine appropriate warrants, maximizing the benefit-cost ratio for limited resources. This paper focuses on two items: first, the numerous types of energy-absorbing guardrail end terminals are identified and delineated and second, a crash reconstruction technique for determining the initial velocity of a vehicle impacting a guardrail end terminal based upon conservation of momentum and conservation of energy is developed. By understanding the types of guardrail terminals and being able to reconstruct real-world crashes, highway planners, designers and maintenance people will have significant more information than is currently available to aid in the goal of mitigating roadside crashes.

Removing the infected aortofemoral graft using a two-stage procedure with a delay between the stages.

This study describes the results of a procedure for removing the infected aortofemoral graft using a two-stage procedure with a delay between the stages. The objective was to lessen the morbidity and mortality associated with removing an infected graft through a single operation. Eight consecutive patients were treated in this manner over a 6-year span. The indications for surgery were infected groin false aneurysms in three, chronic draining sinuses involving the prosthetic graft in four, and an open groin infection involving graft in one. There were five males and three females, with ages ranging 47-83 years (mean = 63). The mean operative time of the first-stage operation was 5.1 hr (range 3.0-7.7), and the mean blood transfusion requirement was 1.7 units. The mean operative time of the second stage operation was 3.5 hr (range 3.5-7.6), and the mean blood transfusion requirement was 2.5 units. In six patients, the hospital course was uncomplicated, with a mean hospital stay of 8.4 days for the initial stage and 9.2 days for the second stage. Two patients had complicated postoperative courses with hospital stays of >30 days. There was no operative or graft-related late mortality. No patients were lost to follow-up. One patient died of unrelated causes with a patent graft at 22 months postsurgery. All other patients remain well with patent grafts, without requiring revisions at a mean follow-up of 33 months (range 6-73). A two-stage approach with a delay between the stages may reduce the morbidity and mortality associated with the removal of an infected aortobifemoral graft.

Parkin suppresses wild-type alpha-synuclein-induced toxicity in SHSY-5Y cells.

Current hypotheses concerning the mechanism of neuronal cell death in Parkinson's disease (PD) and related synucleopathies propose a functional interaction between parkin and alpha-synuclein (alphaS). Recently parkin was shown to suppress mutant alphaS-induced toxicity in primary neurons, providing a basis for an association between these proteins and neuronal loss [Neuron 36 (2000) 1007-1019]. We have asked if a similar association could be made between wild-type (wt) alphaS and parkin. We examined inducible over-expression of alphaS in SHSY-5Y cells through adenoviral infection under conditions which produce cellular toxicity through a reduction in ATP levels. We demonstrate that parkin suppresses toxicity induced by mutant (A53T) and wt alphaS. Parkin over-expression was also associated with the appearance of higher molecular weight alphaS-immunoreactive bands by Western blot analysis. These data, consistent with a protective role for parkin, extend previous findings to include a functional association between parkin and the wt form of alphaS.

Results of prosthetic-vein composite graft with remote popliteal arteriovenous fistula in infragenicular bypass.

OBJECTIVE: The purpose of this study is to report the results of a novel procedure for femoral-distal bypass grafting using a composite graft with an adjunctive remote popliteal fistula distal to the prosthetic portion of the graft. This reconstruction was developed for use in limb salvage in the absence of satisfactory autogenous vein. METHOD: Data were collected prospectively on all patients undergoing this procedure from January 1, 1993 to December 31, 1999. Graft patency was determined from follow-up duplex scanning. Patient survival was determined by clinic follow-up. RESULTS: A total of 43 procedures were performed in 38 patients. In 34 patients, 72 previous arterial operations had been previously performed on the ipsilateral limbs. There were 20 men and 18 women with a mean age of 72 years. The indication for surgery was limb salvage in all, with rest pain in 30, and tissue loss in 13. The outflow artery was the below-knee popliteal artery in 10 and a tibial artery in the remainder. Operative mortality was 6.8%. Mean follow up was 26.9 months. The primary patency was 54% at 12 months. Six reconstructions were revised for a primary assisted patency of 60% at 16 months. Secondary patency was 69% at 16 months. Patient survival was 62% at 2 years and 26% at 5 years. CONCLUSIONS: The technique of composite grafting with remote popliteal arteriovenous fistula may be a useful alternative in infragenicular bypass when a satisfactory autogenous vein is not available.