The use of dextran and carbon dioxide for optical coherence tomography in the superficial femoral artery.

The following case report describes using carbon dioxide (CO2) as contrast media for intravascular optical coherence tomography (OCT) imaging in the superficial femoral artery. For initial OCT imaging, 20 mL of iodinated contrast was used during automated pullback. This was followed by 20 mL of hand-injected dextran 40 in normal saline, and finally hand-injected 50 mL of CO2. CO2 gave comparable erythrocyte clearance and imaging quality compared with dextran and iodinated contrast. To our knowledge, this is the first reported case using both dextran and CO2 with OCT imaging of the superficial femoral artery. Using CO2 is a viable option in patients with contraindications to contrast or dextran use.

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

BACKGROUND: The 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. METHODS: Data 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 manufacturer's 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. RESULTS: All 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. CONCLUSIONS: Despite our limited knowledge about the potential of high-fidelity simulation within the endovascular world, today's 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.

Pulse volume recording does not enhance segmental pressure readings for peripheral arterial disease stratification.

BACKGROUND: Noninvasive vascular laboratory determinations for peripheral arterial disease (PAD) often combine pulse volume recordings (PVRs), segmental pressure readings (SPs), and Doppler waveform traces (DWs) into a single diagnostic report. Our objective was to assess the corresponding diagnostic values for each test when subjected to interpretation by 4 vascular specialists. METHODS: A total of 2226 non-invasive diagnostic reports were reviewed through our institutional database between January 2009 and December 2011. Data from noninvasive records with corresponding angiograms performed within 3 months led to a cohort of 76 patients (89 limbs) for analysis. Four vascular specialists, blinded to the angiographic results, stratified the noninvasive studies as representative of normal, <50% "subcritical," or ≥50% "critical" stenosis at the upper thigh, lower thigh, popliteal, and calf segments using 4 randomized noninvasive modalities: (1) PVR alone; (2) SP alone; (3) SP+DW; and (4) SP+DW+PVR. The angiographic records were independently graded by another 3 evaluators and used as a standard to determine the noninvasive diagnostic values and interobserver agreements for each modality. Statistical tests used include the Fleiss-modified kappa analysis, Kruskal-Wallis analysis of variance with Dunn's multiple comparison test, the Kolmogorov-Smirnov test, and the unpaired t-test with Welch's correction. RESULTS: Interobserver variance for all modalities was high, except for SP. When surveying for any stenosis (<50% and ≥50%), sensitivity (range 25-75%) was lower than specificity (range 50-84%) for all modalities. When surveying for critical stenosis only (≥50%), sensitivity (range 27-54%) was also lower than specificity (range 68-92%). Accuracy for detecting any stenosis with SP+DW was significantly higher than with PVR alone (66 ± 7% vs. 56 ± 12%, P = 0.017). There was a significant reduction in accuracy when including incompressible readings within the SP-only analysis compared with exclusion of incompressible vessels (P = 0.0006). However, the effect of vessel incompressibility on accuracy was removed with the addition of DW (P = 0.17) to the protocol. CONCLUSIONS: SP has the greatest interobserver agreement in evaluation of PAD and can be used preferentially for PAD stratification. Given the lower accuracy of PVR for detecting either subcritical or critical disease, PVR tests can be omitted from the noninvasive vascular examination without a significant reduction in overall diagnostic value and can be reserved for patients with incompressible vessels.

Comparison Between Bench-Top and Computational Modelling of Cerebral Thromboembolism in Ventricular Assist Device Circulation.

Despite improvements in ventricular assist devices (VAD) design, VAD-induced stroke rates remain remarkably high at 14-47%. We previously employed computational fluid dynamics (CFD) to propose adjustment of VAD outflow graft (VAD-OG) implantation to reduce stoke. Herein, we present an in-vitro model of cerebral vessel embolization in VAD-assisted circulation, and compare benchtop results to CFD predictions. The benchtop flow-loop consists of a 3D printed aortic bed using Accura 60 polymer driven by a continuous-flow pump. Three hundred spherical particles simulating thrombi of 2, 3.5, and 5 mm diameters were injected at the mock VAD-OG inlet. A water and glycerin mixture (3.8 cP viscosity) synthetically mimicked blood. The flowrate was adjusted to match the CFD Reynolds number. Catch cans were used to capture and count particles reaching cerebral vessels. VAD-OG geometries were evaluated using comparison of means Z-score range of -1.96 ≤ Z ≤ 1.96 to demonstrate overall agreement between computational and in-vitro techniques. Z-scores were: (i) Z = -1.05 for perpendicular (0°), (ii) Z = 0.32 for intermediate (30°), and (iii) Z = -0.52 for shallow (60°) anastomosis and confirmed agreement for all geometries. This study confirmed added benefits of using a left carotid artery bypass-graft with percent embolization reduction: 22.6% for perpendicular, 21.2% for intermediate, and 11.9% for shallow anastomoses. The shallow anastomosis demonstrated lower degrees of aortic arch flow recirculation, consistent with steady-flow computations. Quantitatively and qualitatively, contemporary steady-flow computational models for predicting VAD-induced cerebral embolization can be achieved in-vitro to validate the CFD equivalent.