John C. Wang

Open surgical or endovascular revascularization for acute limb ischemia

Acute limb ischemia (ALI) is one of the most common vascular emergencies, with high risk for limb loss if it is not treated expediently. Endovascular therapy is less invasive and used increasingly because of patient factors that disfavor open surgery despite limited quality data to support its safety and efficacy. This evidence summary reviews literature from 1990 to 2014, comparing contemporary surgical and endovascular revascularization. Systematic review was performed with emphasis on acuity of presentation, study design, revascularization techniques, limb salvage and mortality rates, and complications. There were 2999 articles identified and 563 abstracts reviewed; 68 articles were reviewed fully and 26 critically appraised. Limb salvage, amputation-free survival, overall survival and mortality, and treatment complications were elucidated, including Medicare outcomes data. Risk factors for amputation and mortality were identified. Surgical or endovascular revascularization for ALI is achievable with acceptable limb salvage and amputation rates, which are not markedly different between the two modalities in the short term. Endovascular therapy and surgery are complementary rather than competing strategies for ALI. Further good-quality clinical trial data are needed to define longer term outcomes.

Endovascular Simulation Leads to Efficiency and Competence in Thoracic Endovascular Aortic Repair Procedures

OBJECTIVEnEndovascular interventions such as thoracic endovascular aortic repair (TEVAR) have largely replaced invasive open procedures, and have been demonstrated to be effective in treating patients. Our study used endovascular simulation to assess the effect of TEVAR rehearsal on surgical trainees at different levels in training.nnnDESIGNnParticipants were oriented on an endovascular simulator and subsequently a simulated TEVAR was performed during 4 separate sessions over a 1-month period. Metrics included total procedure/fluoroscopy time and volume of contrast used. Likert scale qualitative analysis evaluated participant׳s skills involving major procedural steps. Analysis of data across cohorts included 1-way analysis of variance, Kruskal-Wallis, and paired t-tests.nnnSETTINGnAll data were collected at University Hospitals-Case Medical Center, Cleveland, OH.nnnPARTICIPANTSnIn all, 12 trainees in 3 cohorts (student, surgery resident postgraduate year [PGY] 1-3, surgery resident/fellow PGY 4-7, n = 4 each) were recruited.nnnRESULTSnAll trainees reduced total procedure time (mean = 537 ± 148 vs 269 ± 66s, first session vs fourth, P < 0.05, CI: 195-341) and fluoroscopy time (mean = 201 ± 74 vs 110 ± 37s, P < 0.05, CI: 51-132) with TEVAR case progression. The student cohort decreased procedure time from 551 ± 84s to 313 ± 65s (P < 0.05, CI: 189-287) whereas PGYs 1 to 3 decreased procedure time from 591 ± 149s to 264 ± 29s (P < 0.05, CI: 113-541). Use of contrast decreased over time, but the difference was not significant. Participants acquired proficiency after a few runs in most steps of the procedure. The average qualitative score for all groups combined improved significantly (P < 0.03). PGY 4 to 7 trainees had higher technical scores but this was not statistically significant. The initial gap in junior vs senior trainee performance narrowed after a few practice sessions in all aspects evaluated.nnnCONCLUSIONSnTEVAR rehearsal on an endovascular simulator can reduce overall procedure and fluoroscopy time, independent of trainee skill level or experience, as well as improve subjective measures of technical success. Further studies are needed to compare simulator performance to outcomes in live cases.

Principal considerations for the contemporary high-fidelity endovascular simulator design used in training and evaluation

BACKGROUNDnThe simulation and rehearsal of virtual endovascular procedures are anticipated to improve the outcomes of actual procedures. Contemporary, high-fidelity simulation is based on feedback systems that combine concepts of mechanical, electrical, computer, and control systems engineering to reproduce an interactive endovascular case. These sophisticated devices also include psychometric instruments for objective surgical skill assessment. The goal of this report is to identify the design characteristics of commercially available simulators for endovascular procedures and to provide a cross-section comparison across all devices to aid in the simulator selection process.nnnMETHODSnData were obtained (1) by a standard questionnaire issued to four simulator companies prompting for relevant design details of each model for the expressed purpose of publication, (2) from each manufacturers respective website including appended sales brochures and specification sheets, and (3) by an evaluation of peer-reviewed literature. Focus topics include haptic technology, vessel segmentation, physiologic feedback, performance feedback, and physical logistics (ie, weight, dimensions, and portability). All data sources were surveyed between January 1, 2012, and June 30, 2013.nnnRESULTSnAll of the commercially available, high-fidelity endovascular simulators use interactive virtual environments with preprogrammed physics and physiology models for accurate reproduction of surgical reality. The principal differences between devices are the number of access sites and haptic devices, the ability to reconstruct patient-specific anatomy for preprocedural rehearsal, and the available peripheral training modalities. Hardware and software options can also vary within the same device in comparing patient-specific with generic cases.nnnCONCLUSIONSnDespite our limited knowledge about the potential of high-fidelity simulation within the endovascular world, todays currently available simulators successfully provide high-fidelity reproductions of the endovascular environment. We have found that all of the commercially available devices incorporate the necessary features for a high-fidelity experience: (1) haptic technology, (2) vessel reconstruction, (3) physiology feedback, and (4) performance feedback. Significant variations in design do exist and may influence differences in skill development, evaluation, or cost. However, further validation of these differences is still needed and would benefit program directors interested in expanding these platforms for vascular training and certification as this technology matures.

Endovascular aneurysm repair simulation can lead to decreased fluoroscopy time and accurately delineate the proximal seal zone

BACKGROUNDnThe use of simulators for endovascular aneurysm repair (EVAR) is not widespread. We examined whether simulation could improve procedural variables, including operative time and optimizing proximal seal. For the latter, we compared suprarenal vs infrarenal fixation endografts, right femoral vs left femoral main body access, and increasing angulation of the proximal aortic neck.nnnMETHODSnComputed tomography angiography was obtained from 18 patients who underwent EVAR at a single institution. Patient cases were uploaded to the ANGIO Mentor endovascular simulator (Simbionix, Cleveland, Ohio) allowing for three-dimensional reconstruction and adapted for simulation with suprarenal fixation (Endurant II; Medtronic Inc, Minneapolis, Minn) and infrarenal fixation (C3; W. L. Gore & Associates Inc, Newark, Del) deployment systems. Three EVAR novices and three experienced surgeons performed 18 cases from each side with each device in randomized order (nxa0= 72 simulations/participant). The cases were stratified into three groups according to the degree of infrarenal angulation: 0° to 20°, 21° to 40°, and 41° to 66°. Statistical analysis used paired t-test and one-way analysis of variance.nnnRESULTSnMean fluoroscopy time for participants decreased by 48.6% (Pxa0< .0001), and total procedure time decreased by 33.8% (Pxa0< .0001) when initial cases were compared with final cases. When stent deployment accuracy was evaluated across all cases, seal zone coverage in highly angulated aortic necks was significantly decreased. The infrarenal device resulted in mean aortic neck zone coverage of 91.9%, 89.4%, and 75.4% (Pxa0< .0001 by one-way analysis of variance), whereas the suprarenal device yielded 92.9%, 88.7%, and 71.5% (Pxa0< .0001) for the 0° to 20°, 21° to 40°, and 41° to 66° cases, respectively. Suprarenal fixation did not increase seal zone coverage. The side of femoral access for the main body did not influence proximal seal zone coverage regardless of infrarenal angulation.nnnCONCLUSIONSnSimulation of EVAR leads to decreased fluoroscopy times for novice and experienced operators. Side of femoral access did not affect precision of proximal endograft landing. The angulated aortic neck leads to decreased proximal seal zone coverage regardless of infrarenal or suprarenal fixation devices.

Simulation of carotid artery stenting reduces training procedure and fluoroscopy times

Objective: Outcomes from carotid artery stenting (CAS) are related to experience and technical expertise of the operator. Simulation of CAS may enhance clinical proficiency. We interrogated the impact of endovascular simulation of CAS procedures in operators who are at various stages of training. Methods: Twelve trainees (students [n = 4]; junior surgery residents, postgraduate year [PGY] 1‐3 [n = 4]; and senior surgery residents or fellows, PGY 4‐7 [n = 4]) were apprised of characteristics of an endovascular simulator and CAS procedures. This was followed by four independent sessions that were assessed for objective measures including procedure and fluoroscopy times and contrast agent use. A qualitative analysis grading steps of CAS by two observers using a Likert scale was performed. One‐way analysis of variance and paired t‐tests were employed for data analysis. Results: For all participants (n = 12), procedure times (mean, 920 ± 279 seconds for the first session vs 454 ± 156 seconds for the fourth session; P < .01; confidence interval [CI], 315‐621) and fluoroscopy cumulative times (mean, 421 ± 230 seconds for the first session vs 222 ± 102 seconds for the fourth session; P < .01; CI, 78‐285) decreased with progression of cases. Students and PGY 1‐3 residents decreased their procedure times significantly in comparison of initial and final sessions (P < .05 and P < .01, respectively). For all groups, fluoroscopy cumulative times were reduced, and this decrement was significant in the PGY 1‐3 cohort (mean, 444 ± 8 seconds for the first session vs 265 ± 51 seconds for the fourth session; P < .01; CI, 81‐276). Initial CAS procedure times were significantly different between groups (P < .05), but this was observed to resolve by the final case at study completion. Qualitatively, the Likert scores of students and PGY 1‐3 residents significantly improved with case repetition, specifically in the following steps: (1) cannulation of common carotid artery and (2) sizing and deployment of embolic protection device. Senior operators (PGY 4‐7) demonstrated consistently better performance overall with minimal change in scoring with case repetition. Conclusions: Practice leads to improvements in endovascular simulator procedure and fluoroscopy times, especially for more novice trainees. Initial operator performance gaps can be approximated with a few sessions to expected proficiency. Incorporation of endovascular simulators in residency training may assist in shortening the learning curve in rarer endovascular procedures.

Elevated Peak Systolic Velocity and Velocity Ratio from Duplex Ultrasound are Associated with Hemodynamically Significant Lesions in Arteriovenous Access

BACKGROUNDnDuplex ultrasound (DUS) is reliably used to detect lesions in the peripheral andxa0carotid arterial beds and venous system. Although commonly used in clinical practice, duplex criteria to define lesions in arteriovenous access are not well characterized. This studyxa0will define the optimal Doppler-derived peak systolic velocity (PSV) and velocity ratioxa0(VR) to identify >50% lesions in arteriovenous fistulas (AVF) and arteriovenous grafts (AVG).nnnMETHODSnThis retrospective analysis includes patients with both DUS and fistulogram within 30xa0days. DUS-derived PSV and VR were recorded for 3 segments of each access and compared with fistulograms of the same 3 segments of each AV access. Receiver operating characteristic (ROC) was used to determine the optimal DUS criteria for diagnosis of >50% stenosis.nnnRESULTSnFifty pairs of imaging in 40 patients were available for analysis. Mean PSV and VR for segments with greater than 50% stenosis were significantly greater than those without; mean PSV of 480xa0cm/sec vs. 297xa0cm/sec (Pxa0<xa00.001) and mean VR of 3.81 vs. 2.09 (Pxa0<xa00.001). The ROC analysis demonstrated an optimal PSV of 404 and VR of 2.2 to diagnose >50% stenosis with area under the curve of 0.825 and 0.821 for PSV and VR, respectively. PSV of 500 had sensitivity (Se) of 0.60, specificity (Sp) of 0.86, positive predictive value (PPV) of 0.72, and negative predictive value (NPV) of 0.78. VR of 3.0 had Se of 0.52, Sp of 0.91, PPV of 0.77, and NPV of 0.75.nnnCONCLUSIONSnDUS-derived PSV of 400xa0cm/sec and VR of 2.25 have good discrimination to predict greater than 50% stenosis in AVFs and AVGs. Given the broad range of velocities in AV accesses, a threshold of PSV greater than 500xa0cm/sec and VR greater than 3.0, will reliably identify graft-threatening lesions. Se and Sp of PSV 500 are 0.596 and 0.854, respectively. Se and Sp for VR 3.0 are 0.519 and 0.894, respectively.