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Background: There is wide variation in stress test utilization before major vascular surgery and adherence to practice guidelines is unclear. We defined rates of stress test compliance at our institution and led a quality improvement initiative to improve compliance with American Heart Association (ACC/AHA) guidelines., Methods: We implemented a stress testing order set in the electronic medical record at one tertiary hospital. We reviewed all patients who underwent elective, major vascular surgery in the 6 months before (Jan 1, 2022 - Jul 1, 2022) and 6 months after (Aug 1, 2022 - Jan 31, 2023) implementation. We studied stress test guideline compliance, changes in medical or surgical management, and major adverse cardiac events (MACE)., Results: Before order set implementation, 37/122 patients (30%) underwent stress testing within the past year (29 specifically ordered preoperatively) with 66% (19/29) guideline compliance. After order set implementation, 50/173 patients (29%) underwent stress testing within the past year (41 specifically ordered preoperatively) with 80% (33/41) guideline compliance. In the pre- and postimplementation cohorts, stress testing led to a cardiovascular medication change or preoperative coronary revascularization in 24% (7/29) and 27% (11/41) of patients, and a staged surgery or less invasive anesthetic strategy in 14% (4/29) and 4.9% (2/41) of patients, respectively. All unindicated stress tests were surgeon-ordered and none led to a change in management. There was no change in MACE after order set implementation., Conclusions: Electronic medical record-based guidance of perioperative stress testing led to a slight decrease in overall stress testing and an increase in guideline-compliant testing. Our study highlights a need for improved preoperative cardiovascular risk assessment prior to major vascular surgery, which may eliminate unnecessary testing and more effectively guide perioperative decision-making., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose: This study aims to characterize the dependence of measured retinal arterial and venous saturation on vessel diameter and central reflex in retinal oximetry, with an ultimate goal of identifying potential causes and suggesting approaches to improve measurement accuracy., Methods: In 10 subjects, oxygen saturation, vessel diameter and optical density are obtained using Oxymap Analyzer software without diameter correction. Diameter dependence of saturation is characterized using linear regression between measured values of saturation and diameter. Occurrences of negative values of vessel optical densities (ODs) associated with central vessel reflex are acquired from Oxymap Analyzer. A conceptual model is used to calculate the ratio of optical densities (ODRs) according to retinal reflectance properties and single and double-pass light transmission across fixed path lengths. Model-predicted values are compared with measured oximetry values at different vessel diameters., Results: Venous saturation shows an inverse relationship with vessel diameter (D) across subjects, with a mean slope of -0.180 (SE = 0.022) %/μm (20 < D < 180 μm) and a more rapid saturation increase at small vessel diameters reaching to over 80%. Arterial saturation yields smaller positive and negative slopes in individual subjects, with an average of -0.007 (SE = 0.021) %/μm (20 < D < 200 μm) across all subjects. Measurements where vessel brightness exceeds that of the retinal background result in negative values of optical density, causing an artifactual increase in saturation. Optimization of model reflectance values produces a good fit of the conceptual model to measured ODRs., Conclusion: Measurement artefacts in retinal oximetry are caused by strong central vessel reflections, and apparent diameter sensitivity may result from single and double-pass transmission in vessels. Improvement in correction for vessel diameter is indicated for arteries however further study is necessary for venous corrections., (© 2023 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.)

Background: Shared decision-making tools have been underused by clinicians in real-world practice. Changes to the National Coverage Determination by Medicare for carotid stenting greatly expand the coverage for patients, but simultaneously require a shared decision-making interaction that involves the use of a validated tool. Accordingly, our objective was to evaluate the currently available decision aids for carotid stenosis., Methods: We conducted a review of the literature for published work on decision aids for the treatment of carotid disease., Results: Four publications met inclusion criteria. We found the format of the decision aid impacted patient comprehension and decision making, although patient characteristics also played a role in the therapeutic decisions made. Notably, none of the available decision aids included the widely adopted transcarotid artery revascularization as an option., Conclusions: Further work is needed in the development of a widespread validated decision aid instrument for patients with carotid stenosis., Competing Interests: Disclosures None., (Copyright © 2023 Society for Vascular Surgery. All rights reserved.)

Introduction: Hospital readmission after lower extremity arterial bypass (LEB) is common. Patients are often discharged to a facility after LEB as a bridge to home. Our objective was to define the association between discharge to a facility and readmission after LEB., Methods: We used the Vascular Quality Initiative to study patients who underwent LEB from 2017 to 2022. The primary exposure was discharge location. The primary outcome was 30-d hospital readmission., Results: We included 6076 patients across 147 centers. The overall 30-d readmission rate was 18%. Readmission occurred among 15% of patients discharged home, 22% of patients discharged to a rehabilitation facility, and 25% of patients discharged to a nursing home. After controlling for patient and procedural factors, there was no significant association between discharge location and 30-d readmission (rehabilitation versus home odds ratio: 1.06, 95% confidence interval: 0.87-1.29; nursing facility versus home odds ratio: 1.21, 95% confidence interval: 0.99-1.47). Female sex, end-stage renal disease, diabetes, heart failure, pulmonary disease, smoking, preoperative functional impairment, tibial bypass target, critical limb threatening or acute ischemia, and postoperative complications including surgical site infection, change in renal function and graft thrombosis were associated with an increased likelihood of readmission., Conclusions: Patients discharged home after LEB experienced a similar likelihood of readmission as those discharged to a facility. While discharge to a facility may aid in care transitions, it did not appear to lead to reduced 30-d readmissions. The recommended discharge location should be predicated on patient care needs and not as a perceived mechanism to reduce readmissions., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: The Centers for Disease Control and Prevention has made the prevention of in-hospital Clostridium difficile infection a priority. However, whether there is a differential impact of Clostridium difficile on surgical patients remains undefined. Therefore, we quantified the procedure-specific association between postoperative Clostridium difficile and surgical outcomes to define opportunities for targeted quality improvement., Methods: We studied patients undergoing major cardiac, vascular, general, or oncologic procedures using the Vizient database from 2015 to 2019. Our primary exposure was postoperative Clostridium difficile infection. Our primary outcomes were postoperative length of stay, hospitalization cost, readmission, and in-hospital mortality. We used linear and logistic regression for risk adjustment., Results: The incidence of Clostridium difficile infection was 1.6% (n = 6,506/397,750). Patients with Clostridium difficile were older, more comorbid, and more frequently underwent urgent surgery. The median postoperative length of stay was 7 days (interquartile range: 5-11 days), and it was 66% longer among those with Clostridium difficile (P < .001). Similarly, the median hospitalization cost was $31,000 (interquartile range: $20,000-$49,000), and it was 51% greater among patients with Clostridium difficile (P < .001). Postoperative Clostridium difficile was associated with more readmissions after coronary artery bypass grafting, small bowel resection, colectomy, gastrectomy, pancreatectomy, and infrainguinal bypass (adjusted odds ratio range: 1.4-1.7), but not after open aneurysm repair, suprainguinal bypass, or esophagectomy. Clostridium difficile was associated with increased mortality after coronary artery bypass grafting, small bowel resection, colectomy, and infrainguinal bypass (adjusted odds ratio range: 1.3-2.7), but not after open aneurysm repair, suprainguinal bypass, esophagectomy, gastrectomy, or pancreatectomy., Conclusion: Postoperative Clostridium difficile infection was differentially associated with increased length of stay, cost, readmissions, and mortality across specific procedures. This was most apparent after infrainguinal bypass, small bowel resection, colectomy, and coronary artery bypass grafting. Accordingly, a targeted Clostridium difficile reduction effort for these procedures may offer a more effective approach toward reducing infection rates., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: The utilization and cost-effectiveness of stress testing before abdominal aortic aneurysm (AAA) repair remains insufficiently studied. We examined the variation and financial implications of stress testing, and their association with major adverse cardiovascular events (MACE)., Methods: We studied patients who underwent elective endovascular (EVAR) or open AAA repair (OAR) at Vascular Quality Initiative centers from 2015 to 2019. We grouped centers into quintiles of preoperative stress testing frequency. We calculated the risk of postoperative MACE, a composite of in-hospital myocardial infarction, heart failure, or death, for each center-quintile. We obtained charges for stress tests locally and applied these to the cohort to estimate charges per 1000 patients., Results: We studied 32,459 patients (EVAR: 27,978; OAR: 4481; 283 centers). Stress test utilization varied across quintiles from 13.0% to 68.6% (median: 36.8%) before EVAR and 15.9% to 85.0% (median: 59.4%) before OAR. The risk of MACE was 1.4% after EVAR and 10.2% after OAR. There was a trend towards more common MACE after EVAR among centers with higher utilization of stress testing: 0.9% among centers in the lowest quintile, versus 1.7% in the highest quintile ( p -trend = 0.068). There was no association between MACE and stress testing frequency for OAR ( p -trend = 0.223). The estimated financial charges for stress testing before EVAR ranged from $125,806 per 1000 patients at 1 st -quintile centers, to $665,975 at 5 th -quintile centers. Charges before OAR ranged from $153,861 at 1 st -quintile centers, to $825,473 at 5 th -quintile centers., Conclusion: Stress test use before AAA repair is highly variable and associated with substantial cost, with an unclear association with postoperative MACE. This highlights the need for improved stress testing paradigms prior to surgery.

Objective: Conflicting annual procedure volumes have been endorsed among different watchdog groups and professional societies, obscuring credentialing paradigms. There has been ample focus on surgeon volume to date but less attention on the effect of center volume. Specifically, whether center volume might be a better proxy for high-quality care. In the present study, we aimed to measure the association of center volume on open abdominal aortic aneurysm (AAA) repair (OAR) outcomes and failure to rescue (FTR)., Methods: All elective OARs (2003-2020) in the Society for Vascular Surgery Vascular Quality Initiative were reviewed (n = 9791). FTR was defined as in-hospital death after the occurrence of a complication (ie, cardiac, stroke, pulmonary, renal, colonic ischemia, return to the operating room for bleeding). The annual center volume for 218 hospitals was calculated, and the volume quartiles (quartile 1 [Q1], ≤3 procedures/y; quartile 2 [Q2], 4-6 procedures/y; quartile 3 [Q3], 7-10 procedures/y; quartile 4 [Q4], >10 procedures/y) were derived for comparison. Logistic regression was used to estimate the effect of center volume and determine the predictors of FTR., Results: The center volume quartiles and incidence of FTR varied significantly (Q4, 2.5% vs Q1 and Q2, 4.9%; P < .0001; overall FTR, 3.1% [n = 302]). The patients were demographically similar among the quartiles. High-volume centers had used epidural anesthesia more often (Q4, 53%; vs Q1, 31%; P < .0001) but were less likely to use thrombectomy (Q4, 5%; vs Q1, 10%; P < .0001) or any concomitant procedure (Q4, 19%; vs Q1, 22%; P = .05). High-volume centers had had lower rates of pulmonary, renal, and overall complications (pulmonary: Q4, 7%; vs Q1-Q2, 8%-11%; renal: Q4, 16%; vs Q1-2, 19%-21%; P < .0001; overall mean number of complications: Q4, 0.46; vs Q1, 0.52; P = .0008). The crude 30-day and 1-year mortality rates were reduced at the higher volume centers (30 days: Q4, 3%; vs Q1-Q2, 6%; P < .0001; 1 year: Q4, 7%; vs Q1-Q2, 10%-11%; P < .0001). A strong inverse relationship between center volume and FTR was identified (P < .0001). In the adjusted analysis, OARs performed in high-volume centers (Q4 vs Q1) had a 50% risk reduction in FTR (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.3-0.8; P = .004). Among the complications, a return to the operating room for bleeding was most likely to result in FTR (OR, 11.8; 95% CI, 4.3-33; P < .0001). A 24-fold increased risk of FTR was found for patients experiencing three or more complications vs one complication (OR, 24; 95% CI, 17-35; P < .0001)., Conclusions: A greater center volume was strongly associated with significantly diminished FTR, reduced complications, and need for surgical adjuncts during OAR. These findings highlight the utility of center volume as an effective proxy to ensure high-quality aneurysm care., (Copyright © 2022 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Background: Long-segment stenting of the infrarenal aorta and bilateral iliac arteries, with or without femoral endarterectomy for diffuse disease, has been adopted for treatment of severe aortoiliac occlusive disease (AIOD). The objective of this study was to compare outcomes of this reconstruction, termed aortoiliac stenting with bifurcation reconstruction (AISBR), to aortobifemoral bypass (ABF) in patients with comparable TASC II D lesions., Methods: This is a single-center, retrospective review of patients treated with ABF or AISBR for comparable TASC II D lesions between 2010 and 2018. ABF patients were included only if they were deemed anatomic candidates also for AISBR after review of preoperative imaging. Patients treated for acute limb ischemia and bypass graft infection were excluded. Statistics included Fisher exact test, Kaplan-Meier analysis, and Cox proportional hazards regression., Results: There were 24 ABF and 75 AISBR included in the study. The primary indication for treatment was claudication in 55 (55.6%) patients, rest pain in 28 (28.3%), and tissue loss in 16 (16.2%). Patients undergoing AISBR were more likely to be female. Femoral endarterectomies were performed in 37/75 (49.3%) AISBR and 14/24 (58.3%) ABF (P = 0.44). AISBR were performed percutaneously in 34/75 (45.1%). No AISBR required conversion to ABF. Intraoperative blood loss, procedure time and hospital length of stay (LOS) were significantly less for AISBR compared to ABF. Surgical site infections (SSI) were less common in patients undergoing AISBR (AISBR: 6/75 (8.0%) vs. ABF: 9/24 (37.5%), (P< 0.01). One AISBR and two 2 ABF developed late SSI >30 days postoperatively. The reductions in blood loss, LOS and SSI remained significant after excluding percutaneous AISBR from the analysis. Five-year primary patency was 50.8% (95% CI: 33.3, 68.4%) for AISBR and 88.1% (72.7, 100.0%) for ABF (P= 0.04). Five-year survival was 76.5% (95% CI: 63.6, 89.5) for AISBR and 100% (95% CI: 100.0, 100.0) for ABF (P = 0.07). Five-year primary assisted patency, secondary patency, freedom from reintervention and major adverse limb events did not differ significantly between groups., Conclusions: AISBR is a viable option for management of TASC II D AIOD, with lower morbidity and acceptable durability when compared to traditional ABF., (Copyright © 2021. Published by Elsevier Inc.)

Significance: Advances in imaging technology over the last two decades have produced significant innovations in medical imaging. Hyperspectral imaging (HSI) is one of these innovations, enabling powerful new imaging tools for clinical use and greater understanding of tissue optical properties and mechanisms underlying eye disease.Hyperspectral imaging is an important and rapidly growing area in medical imaging, making possible the concurrent collection of spectroscopic and spatial information that is usually obtained from separate optical recordings. In this review, we describe several mainstream techniques used in HSI, along with noteworthy advances in optical technology that enabled modern HSI techniques. Presented also are recent applications of HSI for basic and applied eye research, which include a novel method for assessing dry eye syndrome, clinical slit-lamp examination of corneal injury, measurement of blood oxygen saturation in retinal disease, molecular changes in macular degeneration, and detection of early stages of Alzheimer disease. The review also highlights work resulting from integration of HSI with other imaging tools such as optical coherence tomography and autofluorescence microscopy and discusses the adaptation of HSI for clinical work where eye motion is present. Here, we present the background and main findings from each of these reports along with specific references for additional details., Competing Interests: Conflict of Interest Disclosure: SSM, JMB, and RV are named inventors on patent applications relating to the utility of hyperspectral imagery for diagnosis of neurodegeneration., (Copyright © 2021 American Academy of Optometry.)

Background Patients hospitalized with COVID-19 have an increased risk of thromboembolic events. Whether sex, race or ethnicity impacts these events is unknown. We studied the association between sex, race, and ethnicity and venous and arterial thromboembolic events among adults hospitalized with COVID-19. Methods and Results We used the American Heart Association Cardiovascular Disease COVID-19 registry. Primary exposures were sex and race and ethnicity, as defined by the registry. Primary outcomes were venous thromboembolic events and arterial thromboembolic events. We used logistic regression for risk adjustment. We studied 21 528 adults hospitalized with COVID-19 across 107 centers (54.1% men; 38.1% non-Hispanic White, 25.4% Hispanic, 25.7% non-Hispanic Black, 0.5% Native American, 4.0% Asian, 0.4% Pacific Islander, and 5.9% other race and ethnicity). The rate of venous thromboembolic events was 3.7% and was more common in men (4.2%) than women (3.2%; P <0.001), and in non-Hispanic Black patients (4.9%) than other races and ethnicities (range, 1.3%-3.8%; P <0.001). The rate of arterial thromboembolic events was 3.9% and was more common in men (4.3%) than women (3.5%; P =0.002), and in non-Hispanic Black patients (5.0%) than other races and ethnicities (range, 2.3%-4.7%; P <0.001). Compared with men, women were less likely to experience venous thromboembolic events (adjusted odds ratio [OR], 0.71; 95% CI, 0.61-0.83) and arterial thromboembolic events (adjusted OR, 0.76; 95% CI, 0.66-0.89). Compared with non-Hispanic White patients, non-Hispanic Black patients had the highest likelihood of venous thromboembolic events (adjusted OR, 1.27; 95% CI, 1.04-1.54) and arterial thromboembolic events (adjusted OR, 1.35; 95% CI, 1.11-1.65). Conclusions Men and non-Hispanic Black adults hospitalized with COVID-19 are more likely to have venous and arterial thromboembolic events. These subgroups may represent at-risk patients more susceptible to thromboembolic COVID-19 complications.

Chronic limb-threatening ischemia requires aggressive risk factor management and a thoughtful approach to the complex decision of best strategy for revascularization. Patients often have multilevel disease amenable to endovascular, open surgical, or hybrid approaches. Limited high-quality evidence is available to support a specific strategy; randomized trials are ongoing. Acute limb ischemia is associated with a high risk of limb loss and mortality. Catheter-directed thrombolysis is mainstay of therapy in patients with marginally threatened limbs, whereas those immediately threatened with motor deficits require more rapid restoration of flow with open or endovascular techniques that can establish flow in single setting., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: Stress testing is often used before abdominal aortic aneurysm (AAA) repair. Whether stress testing leads to a reduction in cardiac events after AAA repair has remained unclear. Our objective was to study the national stress test usage rates and compare the perioperative outcomes between centers with high and low usage of stress testing., Methods: We used the Vascular Quality Initiative to study patients who had undergone elective endovascular AAA repair (EVAR) or open AAA repair (OAR). We measured the usage rates of stress testing across centers and compared the Vascular Study Group of New England cardiac risk index (VSG-CRI) among patients who had and had not undergone preoperative stress testing. We determined the rate of major adverse cardiac events (MACE), a composite of perioperative myocardial infarction, stroke, heart failure exacerbation, and death across the centers. We compared the MACE and 1-year mortality between the centers in the highest quintile of stress test usage and the lowest quintile., Results: We studied 43,396 EVAR patients and 8935 OAR patients across 324 centers. The median proportion of stress test usage across centers before EVAR was 35.9% and varied from 10.2% (5th percentile) to 73.7% (95th percentile), with similar variability for OAR (median, 57.9%; 5th percentile, 13.0%; 95th percentile, 86.0%). The mean VSG-CRI for the EVAR group with preoperative stress testing was 5.6 ± 2.1 compared with 5.4 ± 2.1 (P < .001) for the EVAR group without preoperative stress testing. The findings were similar for OAR, with a VSG-CRI of 5.1 ± 2.0 vs 4.8 ± 2.1 (P < .001) for those with and without preoperative stress testing, respectively. The rate of MACE was 1.8% after EVAR and 11.6% after OAR. The 1-year mortality was 4.6% for EVAR and 6.6% for OAR. The centers in the highest quintile of stress testing had a higher adjusted likelihood of MACE after both EVAR (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.37-2.30) and OAR (OR, 1.99; 95% CI, 1.53-2.59) but similar 1-year mortality (EVAR: OR, 1.18; 95% CI, 1.02-1.37; OAR: OR, 0.87; 95% CI, 0.65-1.17) compared with the centers in the lowest quintile. The VSG-CRI was not different between the high stress test centers (EVAR, 5.5 ± 2.1; OAR: 5.0 ± 2.0), and low stress test centers (EVAR, 5.5 ± 2.1; P = .403; OAR, 4.9 ± 2.0; P = .563)., Conclusions: Stress test usage before AAA repair varied widely across Vascular Quality Initiative centers despite similar patient risk profiles. No reduction was observed in MACE or 1-year mortality among centers with high stress test usage. The value of routine stress testing before AAA repair should be reconsidered, and stress testing should be used more selectively, given these findings and the associated costs of widespread testing., (Copyright © 2021. Published by Elsevier Inc.)

Objective: Data regarding the treatment of tandem carotid artery lesions at the bifurcation and ipsilateral, proximal common carotid artery (CCA) are limited. It has been suggested that concomitant treatment with carotid endarterectomy (CEA) and proximal ipsilateral carotid artery stenting confers a high risk of stroke and death. The objective of this study was to evaluate the technique and outcomes of this hybrid procedure at a single institution., Methods: A retrospective chart review was performed including patients who underwent CEA + ipsilateral carotid artery stenting for treatment of atherosclerotic carotid artery disease between December 2007 and April 2017. Primary endpoints were postoperative myocardial infarction, neurologic event, and perioperative mortality., Results: Twenty-two patients (15 male [68%]) underwent CEA + ipsilateral carotid artery stenting with a mean follow-up of 67 ± 77 months. The mean age was 70.0 ± 6.1 years old, all with a prior smoking history (eight current smokers [64%]). Twelve patients (55%) were treated for symptomatic disease and three had a prior ipsilateral CEA (one also with CAS). Computed tomographic angiography imaging was performed preoperatively in 21 patients (95%). CEA was performed first in 18 patients (82%) followed by ipsilateral carotid artery stenting. CEA was performed with a patch in 20 and eversion endarterectomy in two patients. Ipsilateral CCA was stented in 21 patients (96%) and one innominate was stented in a patient with a right CEA. Additional endovascular interventions were performed in three patients: 1 innominate stent, 1 distal ipsilateral internal carotid artery stent, and 1 right subclavian artery stent. All proximal stents were placed with sheath access through the endarterectomy patch in 12 (55%), CCA in 7 (32%), and through the arteriotomy before patching in 3 (14%). Distal internal carotid artery clamping was performed in 18 (90%, available 20) of patients before ipsilateral carotid artery stenting. All proximal lesions were successfully treated endovascularly with no open conversion. One dissection was created and treated effectively with stenting. One perioperative stroke (4.5%) occurred in a patient treated for symptomatic disease, 1 postoperative myocardial infarction (4.5%), and 2 patients (9.1%) with cranial nerve injuries. There was one patient who expired within 30 days, shortly after discharge for unknown reasons. The mean length of stay was 2.6 ± 2.0 days., Conclusions: In appropriately selected patients, concomitant CEA and ipsilateral carotid artery stenting can be safely performed in high-risk patients with a low risk of myocardial infarction, neurologic events, and perioperative mortality when careful surgical technique is used, using direct carotid access, and distal carotid clamping for cerebral protection before stenting., (Copyright © 2019 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

A noninvasive and cost-effective means to detect preclinical Alzheimer's disease (AD) and monitor disease progression would be invaluable. The retina is a developmental extension of the brain and has been viewed as a window to evaluate AD-related pathology. Cross-sectional studies have shown structural changes in the retina of AD patients that include thinning of the retinal nerve-fiber layer and changes in retinal vasculature. However, such changes do not manifest in early stages of the disease nor are they specific biomarkers for AD. Described herein is the utilization of our retinal hyperspectral imaging (rHSI) technique as a biomarker for identification of AD-related early pathological changes in the retina. Specifically, this account concerns the translation of our rHSI technique from animal models to human AD subjects. The underlying principle is Rayleigh light scattering, which is expected from low-order Aβ aggregates present in early pathology. Recruitment was restricted to AD subjects ( N  = 19) and age-matched controls, with no family history of AD ( N  = 16). To limit the influence of skin pigmentation, subjects were restricted to those with skin pigmentation values of 2-3 on the Fitzpatrick scale. The largest spectral deviation from control subjects, rHSI signature, was obtained at the MCI stage with MMSE scores ⩾22, suggesting higher sensitivity of this technique in early disease stages. The rHSI signature observed is unaffected by eye pathologies such as glaucoma and cataract. Age of the subjects minimally influenced the spectral signatures. The rHSI technique shows promise for detection of preclinical AD; it is conducted in a truly noninvasive manner, without application of an exogenous label, and is thus potentially suitable for population screening.

Objective: Repair options for complex abdominal and thoracoabdominal aortic aneurysms (TAAAs) are evolving with increased experience and availability of less invasive endovascular techniques. Identifying risk factors for mortality after fenestrated and branched endovascular aortic repair (F/B-EVAR) could improve patient selection and facilitate decision making regarding who may benefit from prophylactic F/B-EVAR., Methods: We evaluated 1091 patients in a prospective investigational device exemption trial who underwent F/B-EVAR from August 2001 to June 2015 for complex aortic aneurysms (CAAs). Multivariable analysis of risk factors for death was performed using a nonproportional hazards model and a nonparametric analysis using random survival forest technology., Results: Operative mortality after F/B-EVAR was low (3.7%), with high CAA-related survival at 30 day and 5 years (96.8% and 94.0%, respectively). All-cause 5-year survival, however, was 46.2% and older age, heart failure, chronic obstructive pulmonary disease, renal disease, anemia, and coagulation disorders were risk factors. Risk was highest for those undergoing type I/II TAAA repairs and those with larger aneurysms., Conclusions: Patients with multiple comorbidities and those undergoing type I or II TAAA repair are at greatest risk of mortality; however, in this high-risk population, F/B-EVAR offers greater survival compared with that reported for the natural history of untreated aneurysms. Operative and early mortality is lower than the best-reported open repair outcomes, even in this high-risk population, suggesting a potential benefit in extending the use of F/B-EVAR to low-to-average risk CAA patients., (Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Objective: Long-term data regarding the safety and durability of thoracic endovascular aortic repair (TEVAR) are limited. The study objective was to evaluate the long-term outcomes of TEVAR in high-risk patients with descending thoracic aortic pathology., Methods: High-risk patients were treated with thoracic endografts (2001-2011) under a prospective, physician-sponsored, investigational device exemption trial. Three-dimensional reconstructions and measurements were performed on computed tomography scans acquired before discharge, at 1, 6, and 12 months, and then yearly thereafter., Results: The study included 200 patients, of whom 171 were treated for thoracic aneurysm, 28 for chronic dissection, and 1 for aortobronchial fistula. Patients were monitored for an average of 4.8 ± 3.3 years, and 93 (46.5%) were monitored for >5 years. Operative mortality was 6.5%. Survival at 30 days and at 1, 5, and 9 years was 94.0%, 85.8%, 55.6%, and 31.4%, and freedom from aneurysm-related death was 94.0%, 92.4%, 91.7%, 91.7%, respectively. Sixty-one endoleaks occurred in 54 patients (28%). Sixty-seven reinterventions were performed in 50 patients. Overall freedom from reintervention at 30 days, 1, 5, and 9 years was 87.9%, 82.9%, 75.5%, and 64.0%, respectively. Forty-seven reinterventions (70%) were thoracic aneurysm-related, 35 (74%) of which were endovascular procedures. Thirty of these were to correct endoleaks at a median of 1.4 years (interquartile range, 0.2-5.0 years)., Conclusions: TEVAR is durable and associated with high long-term aneurysm-related survival. Long-term imaging follow-up remains critical to identify endoleaks or rare device durability issues, most of which can be monitored or managed with endovascular therapies., (Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Purpose: To describe a spectral imaging system for small animal studies based on noninvasive endoscopy of the retina, and to present time-resolved spectral changes from live Alzheimer's mice prior to cognitive decline, corroborating our previous in vitro findings., Methods: Topical endoscope fundus imaging was modified to use a machine vision camera and tunable wavelength system for acquiring monochromatic images across the visible to near-infrared spectral range. Alzheimer's APP/PS1 mice and age-matched, wild-type mice were imaged monthly from months 3 through 8 to assess changes in the fundus reflection spectrum. Optical changes were fit to Rayleigh light scatter models as measures of amyloid aggregation., Results: Good quality spectral images of the central retina were obtained. Short-wavelength reflectance from Alzheimer's mice retinae showed significant reduction over time compared to wild-type mice. Optical changes were consistent with an increase in Rayleigh light scattering in neural retina due to soluble Aβ1-42 aggregates. The changes in light scatter showed a monotonic increase in soluble amyloid aggregates over a 6-month period, with significant build up occurring at 7 months., Conclusions: Hyperspectral imaging technique can be brought inexpensively to the study of retinal changes caused by Alzheimer's disease progression in live small animals. A similar previous finding of reduction in the light reflection over a range of wavelengths in isolated Alzheimer's mice retinae, was reproducible in the living Alzheimer's mice. The technique presented here has a potential for development as an early Alzheimer's retinal diagnostic test in humans, which will support the treatment outcome.

A new method of interferometry employing a Fabry-Perot etalon model was used to locate and size microscale features on the surface of the pine bark beetle. Oscillations in the reflected light spectrum, caused by self-interference of light reflecting from surfaces of foreleg setae and spores on the elytrum, were recorded using white light hyperspectral microscopy. By making the assumption that pairs of reflecting surfaces produce an etalon effect, the distance between surfaces could be determined from the oscillation frequency. Low frequencies of less than 0.08 nm(-1) were observed in the spectrum below 700 nm while higher frequencies generally occupied wavelengths from 600 to 850 nm. In many cases, two frequencies appeared separately or in combination across the spectrum. The etalon model gave a mean spore size of 3.04 ± 1.27 μm and a seta diameter of 5.44 ± 2.88 μm. The tapering near the setae tip was detected as a lowering of frequency. Spatial fringes were observed together with spectral oscillations from surfaces on the exoskeleton at higher magnification. These signals were consistent with embedded multi-layer reflecting surfaces. Possible applications for hyperspectral interferometry include medical imaging, detection of spore loads in insects and other fungal carriers, wafer surface and subsurface inspection, nanoscale materials, biological surface analysis, and spectroscopy calibration. This is, to our knowledge, the first report of oscillations directly observed by microscopy in the reflected light spectra from Coleoptera, and the first demonstration of broadband hyperspectral interferometry using microscopy that does not employ an internal interferometer., (© 2015 Wiley Periodicals, Inc.)

Treatment of severe aortoiliac disease has dramatically evolved from a dependence on open aortobifemoral grafting to hybrid and endovascular only approaches. Open surgery has been the gold standard treatment of severe aortoiliac disease with excellent patency rates, but with increased length of stay and major complications. In contrast, endovascular interventions can successfully treat almost any lesion with decreased risk, compared to open surgery. Although primary patency rates remain inferior, secondary endovascular interventions are often minor procedures resulting in comparable long-term outcomes. The risks of renal insufficiency, embolization and access complications are not insignificant; however, most can be prevented or managed without significant clinical consequence. Endovascular therapies should be considered a first-line treatment option for all patients with aortoiliac disease, especially those with high-risk cardiovascular comorbidities.

Although a number of different antibiotics are used to combat staphylococcal infections, resistance has continued to develop. The use of rifampicin and ciprofloxacin in combination with azithromycin, known for its inhibitory effects on the bacterial ribosome, can create potential synergistic effects on ribosomal subunit synthesis rates. In this work, combination antibiotic treatments gave a significant decrease in cell numbers following growth in the presence of ciprofloxacin or rifampicin with azithromycin compared to those grown with azithromycin or rifampicin alone. DNA, RNA and protein synthesis rates were reduced with single antibiotic treatments and showed further decreases when drug combinations were used. 70S ribosome levels were reduced with every antibiotic treatment. DNA gyrase subunits A and B showed significant decreases for double and triple antibiotic-treated samples. Ribosomal subunit synthesis rates were diminished for each different antibiotic combination. Turnover of 16S and 23S rRNA was also observed in each case and was stimulated by antibiotic combinations. The frequency of spontaneous resistance was reduced in all double selections, and no triply resistant mutants were found.

Objectives: We sought to understand the factors modulating left heart reverse remodeling after aortic valve replacement, the relationship between the preoperative symptoms and modulators of left heart remodeling, and their influence on long-term survival., Methods: From October 1991 to January 2008, 4264 patients underwent primary aortic valve replacement for aortic stenosis. Changes in the time course of left ventricular reverse remodeling were assessed using 5740 postoperative transthoracic echocardiograms from 3841 patients., Results: Left ventricular hypertrophy rapidly declined after surgery, from 137 ± 42 g/m(2) preoperatively to 115 ± 27 by 2 years and remained relatively constant but greater than the upper limit of normal. The most important risk factor for residual left ventricular hypertrophy was greater preoperative left ventricular hypertrophy (P < .0001). Other factors included a greater left atrial diameter (reflecting diastolic dysfunction), a lower ejection fraction, and male gender. An increased postoperative transprosthesis gradient was associated with greater residual left ventricular hypertrophy; however, its effect was minimal. Preoperative severe left ventricular hypertrophy and left atrial dilatation reduced long-term survival, independent of symptom status., Conclusions: Severe left ventricular hypertrophy with left atrial dilatation can develop from severe aortic stenosis, even without symptoms. These changes can persist, are associated with decreased long-term survival even after successful aortic valve replacement, and could be indications for early aortic valve replacement if supported by findings from an appropriate prospective study., (Copyright © 2014 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Although mechanical loading is known to influence trabecular bone adaptation, the role of specific loading parameters requires further investigation. Previous studies demonstrated that the number of loading cycles and loading duration modulate the adaptive response of trabecular bone in a rabbit model of applied loading. In the current study, we investigated the influence of load magnitude on the adaptive response of trabecular bone using the rabbit model. Cyclic compressive loads, producing peak pressures of either 0.5 or 1.0 MPa, were applied daily (5 days/week) at 1 Hz and 50 cycles/day for 4 weeks post-operatively to the trabecular bone on the lateral side of the distal right femur, while the left side served as an nonloaded control. The adaptive response was characterized by microcomputed tomography and histomorphometry. Bone volume fraction, bone mineral content, tissue mineral density, and mineral apposition rate (MAR) increased in loaded limbs compared to the contralateral control limbs. No load magnitude dependent difference was observed, which may reflect the critical role of loading compared to the operated, nonloaded contralateral limb. The increased MAR suggests that loading stimulated new bone formation rather than just maintaining bone volume. The absence of a dose-dependent response of trabecular bone observed in this study suggests that a range of load magnitudes should be examined for biophysical therapies aimed at augmenting current treatments to enhance long-term fixation of orthopedic devices., (Copyright © 2013 Orthopaedic Research Society.)

Objectives: The study sought to contrast risk profiles and compare outcomes of patients with severe aortic stenosis (AS) and coronary artery disease (CAD) who underwent aortic valve replacement (AVR) and coronary artery bypass grafting (AS+CABG) with those of patients with isolated AS who underwent AVR alone., Background: In patients with severe AS, CAD is often an incidental finding with underappreciated survival implications., Methods: From October 1991 to July 2010, 2,286 patients underwent AVR+CABG and 1,637 AVR alone. A propensity score was developed and used for matched comparisons of outcomes (1,082 patient pairs). Analyses of long-term mortality were performed for each group, then combined to identify common and unique risk factors., Results: Patients with AS+CAD versus isolated AS were older, more symptomatic, and more likely to be hypertensive, and had lower ejection fraction and greater arteriosclerotic burden but less severe AS. Hospital morbidity and long-term survival were poorer (43% vs. 59% at 10 years). Both groups shared many mortality risk factors; however, early risk among AS+CAD patients reflected effects of CAD; late risk reflected diastolic left ventricular dysfunction expressed as ventricular hypertrophy and left atrial enlargement. Patients with isolated AS and few comorbidities had the best outcome, those with CAD without myocardial damage had intermediate outcome equivalent to propensity-matched isolated AS patients, and those with CAD, myocardial damage, and advanced comorbidities had the worst outcome., Conclusions: Cardiovascular risk factors and comorbidities must be considered in managing patients with severe AS. Patients with severe AS and CAD risk factors should undergo early diagnostics and AVR+CABG before ischemic myocardial damage occurs., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objective: Granulomatosis with polyangiitis (Wegener's) (GPA) is a necrotizing granulomatous vasculitis affecting the upper and lower respiratory tract, kidneys, and other small vessels throughout multiple organ systems. Recently, classification criteria for childhood GPA have been proposed and include the addition of airway stenosis. Airway inflammation occurs more frequently in children than adults and often proves difficult to diagnose and treat. Our objectives were to 1) determine the frequency of airway involvement in a cohort of children with GPA as defined by the European League Against Rheumatism/Paediatric Rheumatology International Trials Organisation/Pediatric Rheumatology European Society (EULAR/PRINTO/PRES) criteria, 2) document the frequency of specific airway findings, and 3) review our treatment approach to children with GPA-related airway disease., Methods: A retrospective chart review was performed on patients ages <18 years with a diagnosis of vasculitis evaluated at the Cleveland Clinic between 2004 and 2010., Results: Twenty-eight patients fulfilling the EULAR/PRINTO/PRES classification criteria for the diagnosis of childhood GPA were included in the analysis. There was a mean followup time of 3.1 years. The overall prevalence of any airway disease was 86%, with upper airway involvement in 86% and laryngotracheobronchial (LTB) disease in 50% of patients. LTB disease was present at diagnosis in 36%, while in the remaining 14% it developed on immunosuppressive therapy. Ten patients underwent a successful endoscopic intervention., Conclusion: Airway manifestations frequently occur in childhood GPA. Inflammatory changes can occur at any point in the disease course, necessitating diligent surveillance. Endoscopic interventions for LTB stenotic lesions represent a safe and effective therapeutic option., (Copyright © 2012 by the American College of Rheumatology.)

Background: Rodent lumbar and caudal (tail) spine segments provide useful in vivo and in vitro models for human disc research. In vivo caudal models allow characterization of the effect of static and dynamic loads on disc mechanics of individual animals with time, but the lumbar models have required sacrifice of the animals for in vitro mechanical testing., Questions/purposes: We therefore developed a novel displacement controlled in vivo lumbar spine noninvasive induced angular displacement (NIAD) test; data obtained with NIAD were used to compare angular displacement between segmental levels (L4/L5, L5/L6 and L6/S1), interobserver radiograph measurement agreement, and intraobserver radiograph measurement repeatability. Measurements from NIAD were compared with angular displacement, bending stiffness, and moment to failure measured by an in vitro test., Methods: Anesthetized Lewis rats were xrayed in a 90° angled fixture, and NIAD was measured at lumbar levels L4 to S1 by two independent and blinded observers. After euthanasia, in vitro angular displacement (IVAD), stiffness, and failure moment were measured for the combined L4-L6 segment in four-point bending., Results: NIAD was greater at L4/L5 and L5/L6 than at L6/S1. Combined coronal NIAD for L4-L6 was 42.8° ± 5.3° and for IVAD was 61.5° ± 3.8°. Reliability assessed by intraclass correlation coefficient (ICC) was 0.905 and 0.937 for intraobserver radiograph measurements, and interobserver ICCs ranged from 0.387 to 0.653 for individual levels. The interobserver ICC was 0.911 for combined data from all levels. Reliability for test-retest NIAD measurements had an ICC of 0.932. In vitro failure moment correlated with NIAD left bending., Conclusions: The NIAD method yielded reproducible and reliable rat lumbar spine angular displacement measurements without required euthanasia, and allows repetitive monitoring of animals with time. For lumbar spine research studies performed during a course of time, the NIAD method may reduce animal numbers required by providing serial angular displacement measurements without euthanasia., Clinical Relevance: Improved methods to assess comparative models for disease or aging may permit enhanced clinical treatments and improved patient care.

Purpose: Glaucoma may involve disturbances in retinal oxygenation and blood flow. The purpose of this study was to measure the effect of glaucoma filtration surgery on retinal vessel oxygen saturation., Methods: A noninvasive spectrophotometric retinal oximeter was used to measure hemoglobin oxygen saturation in retinal arterioles and venules before and after glaucoma filtration surgery. Twenty-five consecutive patients were recruited, and 19 had adequate image quality. Fourteen underwent trabeculectomy and five glaucoma tube surgery. Twelve had primary open-angle glaucoma and seven had exfoliative glaucoma. IOP decreased from 23 +/- 7 to 10 +/- 4 mm Hg (mean +/- SD, P = 0.0001)., Results: Oxygen saturation increased in retinal arterioles from 97% +/- 4% to 99% +/- 6% (n = 19; P = 0.046) after surgery and was unchanged in venules (63% +/- 5% before surgery and 64% +/- 6% after, P = 0.76). There were no significant changes in saturation in the fellow eyes (P > 0.60). The arteriovenous difference was 34% before and 36% after surgery (P = 0.35)., Conclusions: Glaucoma filtration surgery had almost no effect on retinal vessel oxygen saturation.

Purpose: Animal studies have indicated that retinal oxygen consumption is greater in dark than light. In this study, oxygen saturation is measured in retinal vessels of healthy humans during dark and light., Methods: The oximeter consists of a fundus camera, a beam splitter, a digital camera and software, which calculates hemoglobin oxygen saturation in the retinal vessels. In the first experiment, 18 healthy individuals underwent oximetry measurements after 30 minutes in the dark, followed by alternating 5-minute periods of white light (80 cd/m(2)) and dark. In the second experiment, 23 volunteers underwent oximetry measurements after 30 minutes in the dark, followed by light at 1, 10, and 100 cd/m(2). Three subjects were excluded from analysis in the first experiment and four in the second experiment because of poor image quality., Results: In the first experiment, the arteriolar saturation decreased from 92% +/- 4% (n = 15; mean +/- SD) after 30 minutes in the dark to 89% +/- 5% after 5 minutes in the light (P = 0.008). Corresponding numbers for venules are 60% +/- 5% in the dark and 55% +/- 10% (P = 0.020) in the light. In the second experiment, the arteriolar saturation was 92% +/- 4% in the dark and 88% +/- 7% in 100 cd/m(2) light (n = 19, P = 0.012). The corresponding values for venules were 59% +/- 9% in the dark and 55% +/- 10% in 100 cd/m(2) light (P = 0.065)., Conclusions: Oxygen saturation in retinal blood vessels is higher in dark than in 80 or 100 cd/m(2) light in human retinal arterioles and venules. The authors propose that this is a consequence of increased oxygen demand in the outer retina in the dark.

This updates an earlier publication by the authors describing a robust framework for detecting vasculature in noisy retinal fundus images. We improved the handling of the "central reflex" phenomenon in which a vessel has a "hollow" appearance. This is particularly pronounced in dual-wavelength images acquired at 570 and 600 nm for retinal oximetry. It is prominent in the 600 nm images that are sensitive to the blood oxygen content. Improved segmentation of these vessels is needed to improve oximetry. We show that the use of a generalized dual-Gaussian model for the vessel intensity profile instead of the Gaussian yields a significant improvement. Our method can account for variations in the strength of the central reflex, the relative contrast, width, orientation, scale, and imaging noise. It also enables the classification of regular and central reflex vessels. The proposed method yielded a sensitivity of 72% compared to 38% by the algorithm of Can et al., and 60% by the robust detection based on a single-Gaussian model. The specificity for the methods were 95%, 97%, and 98%, respectively.

This paper presents an automated method to identify arteries and veins in dual-wavelength retinal fundus images recorded at 570 and 600 nm. Dual-wavelength imaging provides both structural and functional features that can be exploited for identification. The processing begins with automated tracing of the vessels from the 570-nm image. The 600-nm image is registered to this image, and structural and functional features are computed for each vessel segment. We use the relative strength of the vessel central reflex as the structural feature. The central reflex phenomenon, caused by light reflection from vessel surfaces that are parallel to the incident light, is especially pronounced at longer wavelengths for arteries compared to veins. We use a dual-Gaussian to model the cross-sectional intensity profile of vessels. The model parameters are estimated using a robust M-estimator, and the relative strength of the central reflex is computed from these parameters. The functional feature exploits the fact that arterial blood is more oxygenated relative to that in veins. This motivates use of the ratio of the vessel optical densities (ODs) from images at oxygen-sensitive and oxygen-insensitive wavelengths (ODR = OD600/OD570) as a functional indicator. Finally, the structural and functional features are combined in a classifier to identify the type of the vessel. We experimented with four different classifiers and the best result was given by a support vector machine (SVM) classifier. With the SVM classifier, the proposed algorithm achieved true positive rates of 97% for the arteries and 90% for the veins, when applied to a set of 251 vessel segments obtained from 25 dual wavelength images. The ability to identify the vessel type is useful in applications such as automated retinal vessel oximetry and automated analysis of vascular changes without manual intervention.

The cytotoxic response of cells in culture is dependant on the degree of functionalization of the single-walled carbon nanotube (SWNT). After characterizing a set of water-dispersible SWNTs, we performed in vitro cytotoxicity screens on cultured human dermal fibroblasts (HDF). The SWNT samples used in this exposure include SWNT-phenyl-SO(3)H and SWNT-phenyl-SO(3)Na (six samples with carbon/-phenyl-SO(3)X ratios of 18, 41, and 80), SWNT-phenyl-(COOH)(2) (one sample with carbon/-phenyl-(COOH)(2) ratio of 23), and underivatized SWNT stabilized in 1% Pluronic F108. We have found that as the degree of sidewall functionalization increases, the SWNT sample becomes less cytotoxic. Further, sidewall functionalized SWNT samples are substantially less cytotoxic than surfactant stabilized SWNTs. Even though cell death did not exceed 50% for cells dosed with sidewall functionalized SWNTs, optical and atomic force microscopies show direct contact between cellular membranes and water-dispersible SWNTs; i.e. the SWNTs in aqueous suspension precipitate out and selectively deposit on the membrane.

Alkylation of nanotube salts prepared using either lithium, sodium, or potassium in liquid ammonia yields sidewall-functionalized nanotubes that are soluble in organic solvents. Atomic force microscopy and transmission electron microscopy studies of dodecylated SWNTs prepared from HiPco nanotubes and 1-iodododecane show that extensive debundling results from intercalation of the alkali metal into the SWNT ropes. TGA-FTIR analyses of samples prepared from the different metals revealed radically different thermal behavior during detachment of the dodecyl groups. The SWNTs prepared using lithium can be converted into the pristine SWNTs at 180-330 degrees C, whereas the dodecylated SWNTs prepared using sodium require a much higher temperature (380-530 degrees C) for dealkylation. SWNTs prepared using potassium behave differently, leading to detachment of the alkyl groups over the temperature range 180-500 degrees C. These differences can be observed by analysis of the solid-state 13C NMR spectra of the dodecylated SWNTs that have been prepared using the different alkali metals and may indicate differences in the relative amounts of 1,2- and 1,4-addition of the alkyl groups.

[reaction: see text] Carbon nanotube salts prepared by treating single-wall carbon nanotubes (SWNTs) with lithium in liquid ammonia react readily with aryl iodides to give SWNTs functionalized by aryl groups.

We present an automated method to perform accurate, rapid, and objective measurement of the blood oxygen saturation over each segment of the retinal vascular hierarchy from dual-wavelength fundus images. Its speed and automation (2 s per entire image versus 20 s per segment for manual methods) enables detailed level-by-level measurements over wider areas. An automated tracing algorithm is used to estimate vessel centerlines, thickness, directions, and locations of landmarks such as bifurcations and crossover points. The hierarchical structure of the vascular network is recovered from the trace fragments and landmarks by a novel algorithm. Optical densities (OD) are measured from vascular segments using the minimum reflected intensities inside and outside the vessel. The OD ratio (ODR=OD600/OD570) bears an inverse relationship to systemic HbO2 saturation (SO2). The sensitivity for detecting saturation change when breathing air versus pure oxygen was calculated from the measurements made on six subjects and was found to be 0.0226 ODR units, which is in good agreement with previous manual measurements by the dual-wavelength technique, indicating the validity of the automation. A fully automated system for retinal vessel oximetry would prove useful to achieve early assessments of risk for progression of disease conditions associated with oxygen utilization.

Purpose: To evaluate a hyperspectral imaging technique for monitoring relative spatial changes in retinal oxygen saturation., Methods: The optic nerve head (ONH) and overlying vessels in cynomolgus monkey eyes were imaged with a fundus camera attached to a hyperspectral imaging system. Images were acquired with inspiration of room air and pure oxygen and at controlled intraocular pressures (IOP) of 15 mm Hg (normal) and 60 mm Hg (sustained for up to 5 minutes). Changes in relative blood oxygen saturation in the vessels and ONH were assessed from reflectance spectra. Saturation maps were derived from contributions of oxygenated and deoxygenated hemoglobin spectral signatures extracted from hyperspectral images. The results obtained with hyperspectral imaging were compared with known experimental outcomes., Results: Pure oxygen markedly increased oxygen saturation in veins. Increases in arteries and the ONH were smaller. The results obtained with hyperspectral image analysis agreed with known changes in oxygen saturation from breathing experiments. Raising IOP reduced saturation in all structures and resulted in profound desaturation of arteries. During sustained high IOP, a rebound in saturation was observed in the ONH. Spatial maps clearly showed the saturation changes in arteries, veins, and surrounding tissues., Conclusions: Hyperspectral imaging can be adapted to measure and map relative oxygen saturation in retinal structures and the ONH in nonhuman primate eyes.

Previous measurements of transmembrane potential using the electrochromic probe di-8-ANEPPS have used the excitation spectral shift response by alternating excitation between two wavelengths centered at voltage-sensitive portions of the excitation spectrum and recording at a single wavelength near the peak of the emission spectrum. Recently, the emission spectral shift associated with the change in transmembrane potential has been used for continuous membrane potential monitoring. To characterize this form of the electrochromic response from di-8-ANEPPS, we have obtained fluorescence signals from single cells in response to step changes in transmembrane potentials set with a patch electrode, using single wavelength excitation near the peak of the dye absorption spectrum. Fluorescence changes at two wavelengths near voltage-sensitive portions of the emission spectrum and shifts in the complete emission spectrum were determined for emission from plasma membrane and internal membrane. We found that the fluorescence ratio from either dual-wavelength recordings, or from opposite sides of the emission spectrum, varied linearly with the amplitude of the transmembrane potential step between -80 and +60 mV. Voltage dependence of difference spectra exhibit a crossover point near the peak of the emission spectra with approximately equal gain and loss of fluorescence intensity on each side of the spectrum and equal response amplitude for depolarization and hyperpolarization. These results are consistent with an electrochromic mechanism of action and demonstrate how the emission spectral shift response can be used to measure the transmembrane potential in single cells.

Introduction: We hypothesized that intracellular calcium overload may play an important role in heat-induced myocardial injury. This postulate was investigated using a model of isolated guinea pig papillary muscle in which resting tension was measured as an indirect indicator of cytosolic free-calcium concentration and the fluorescence changes of Fluo-3 AM dye was measured as a direct indicator of cytosolic free-calcium concentration., Methods and Results: Excised guinea pig right ventricular papillary muscles were attached to a force transducer in a high-flow tissue bath and superfused with Tyrode's solution at 37 degrees +/- 0.5 degrees C. The temperature was rapidly changed to between 38.0 degrees and 56.0 degrees C for 60 seconds and then returned to 37.0 degrees C. Hyperthermia caused a reversible increase in resting tension at temperatures between 45 degrees and 50 degrees C and irreversible contracture at > or =50 degrees C. Rapid cooling contracture experiments and experiments measuring fluorescence of myocytes loaded with 5 microM Fluo-3 AM dye demonstrated that the hyperthermia-induced rise in resting tension was likely due to an increase in intracellular calcium content. Inhibition of the sarcoplasmic reticulum calcium pump with 20 microM thapsigargin resulted in irreversible contracture of the papillary muscles at temperatures between 45 degrees and 50 degrees C and significant increases in Fluo-3 fluorescence at 48 degrees C. Blockade of sarcolemmal calcium channels with 0.5 mM cadmium or 40 microM verapamil did not attenuate the heat-induced increase in resting tension and Fluo-3 fluorescence., Conclusion: Hyperthermia causes an increase in resting tension of cardiac muscle that most likely is mediated by a calcium channel-independent increase in calcium permeability of the sarcolemmal membrane and/or release of stored intracellular calcium.

A method for noninvasive measurement of Hb O2 saturation (SO2) in retinal blood vessels by digital imaging was developed and tested. Images of vessels were recorded at O2-sensitive and O2-insensitive wavelengths (600 and 569 nm, respectively) by using a modified fundus camera with an image splitter coupled to an 18-bit digital camera. Retinal arterial SO2 was varied experimentally by having subjects breathe mixtures of O2 and N2 while systemic arterial SO2 was monitored with a pulse oximeter. Optical densities (ODs) of vascular segments were determined using a computer algorithm to track the path of reflected light intensity along vessels. During graded hypoxia the OD ratio (ODR = OD600/OD569) bore an inverse linear relationship to systemic SO2. Compensation for the influence of choroidal pigmentation significantly reduced variation in the arterial SO2 measurements among subjects. An O2 sensitivity of 0.00504 +/- 0.00029 (SE) ODR units/%SO2 was determined. Retinal venous SO2 at normoxia was 55 +/- 3.38% (SE). Breathing 100% O2 increased venous SO2 by 19.2 +/- 2.9%. This technique, when combined with blood flow studies in human subjects, will enable the study of retinal O2 utilization under experimental and various disease conditions.

In this report we demonstrate electrical communication in the microcirculation between arterioles and capillary networks in situ. Microvessel networks in the hamster cheek pouch, which included capillaries and their feeding arterioles, were labeled with the voltage-sensitive dye di-8-ANEPPS by intraluminal perfusion through a micropipette. Pulses of 140 mM potassium solution were applied by pressure ejection from micropipettes positioned on arterioles several hundred micrometers upstream from capillaries. Potassium caused membrane potential changes of 3-11 mV in capillary segments up to 1,200 micrometers distal to the stimulation site, with time delays of <1 s. Capillary membrane potential changes were biphasic, with initial depolarizations followed by hyperpolarizations. The size of the response decreased exponentially with the distance between the arteriole and capillary, with a 1/e distance of 590 micrometers. The time to peak depolarization of both arteriolar and capillary segments was similar. The time to peak response was significantly faster than that for responses from direct stimulation of capillaries. Capillary responses were also obtained when blood flow was either blocked or directed toward sites of stimulation. Acetylcholine (10(-4) M) and phenylephrine (10(-5) M) applied to the arterioles by iontophoresis produced monophasic hyperpolarizing and depolarizing responses, respectively, in capillaries with <1-s delay between stimulus and onset of the membrane potential change. These results provide evidence in situ of a pathway for electrical communication between arteriolar and capillary levels of the microcirculation.

Objective: This study aimed to determine whether retinal oxygen consumption in patients with diabetes without retinopathy is affected by acute changes in blood glucose., Design: The study design was a nonrandomized, interventional clinical study., Participants: The study consisted of 12 patients with diabetes without ophthalmoscopically visible diabetic retinopathy whose ages were 20 to 59 years (mean, 33.7 years)., Intervention: Retinal vessel oximetry was performed on subjects during normoglycemia and during acutely induced hyperglycemia. Hyperglycemia was achieved with the ingestion of an oral glucose load., Main Outcome Measures: Changes in retinal arterial and venous blood oxygen saturation resulting from systemic blood glucose changes were measured. Measurements were made using a noninvasive, two-wavelength digital imaging retinal vessel oximeter., Results: In each subject, the measured retinal venous blood oxygen saturation decreased significantly during hyperglycemia. The amount of decrease in venous oxygen saturation associated with hyperglycemia was positively correlated with the duration of diabetes. The measured retinal arterial oxygen saturation did not change significantly during hyperglycemia., Conclusions: These results, taken with the observations of numerous other investigators that show increased blood flow during acute hyperglycemia, provide evidence of substantially increased retinal oxygen consumption during hyperglycemia. The results also complement previous observations of the effect of diabetes on retinal autoregulation.

It has been proposed that capillaries can detect changes in tissue metabolites and generate signals that are communicated upstream to resistance vessels. The mechanism for this communication may involve changes in capillary endothelial cell membrane potentials which are then conducted to upstream arterioles. We have tested the capacity of capillary endothelial cells in vivo to respond to pharmacological stimuli. In a hamster cheek pouch preparation, capillary endothelial cells were labeled with the voltage-sensitive dye di-8-ANEPPS. Fluorescence from capillary segments (75-150 microns long) was excited at 475 nm and recorded at 560 and 620 nm with a dual-wavelength photomultiplier system. KCl was applied using pressure injection, and acetylcholine (ACh) and phenylephrine (PE) were applied iontophoretically to these capillaries. Changes in the ratio of the fluorescence emission at two emission wavelengths were used to estimate changes in the capillary endothelial membrane potential. Application of KCl resulted in depolarization, whereas application of the vehicle did not. Application of ACh and PE resulted in hyperpolarization and depolarization, respectively. The capillary responses could be blocked by including a receptor antagonist (atropine or prazosin, respectively) in the superfusate. We conclude that the capillary membrane potential is capable of responding to pharmacological stimuli. We hypothesize that capillaries can respond to changes in the milieu of surrounding tissue via changes in endothelial membrane potential.

An LED light source for dual-wavelength calibration of light microscope recording systems is described. A 1 mm2 circular field of bi-chromatic illumination is formed by passing the crossed beams of two light emitting diodes (LEDS) through an optical diffuser and circular mask. The source is constructed using LEDs which emit light at wavelengths overlapping those of many of the dual-emission molecular probes used for measurement of calcium, pH and membrane potential. The light output can be independently varied to set the ratio of light intensities recorded at two wavelengths. Internally sampled voltages which are proportional to LED light output intensity provide an internal reference for comparison with optical recordings. The LED source is useful for obtaining the optical response of dual emission recording equipment for specific recording conditions defined by the filtering and light detection components of the system.

A fluorescence ratio technique based on the voltage-sensitive dye 1-(3-sulfonatopropyl)-8-[beta-[2-di-n-butylamino)-6-naphythyl++ +]vinyl] pyridinium betaine (di-8-ANEPPS)has been developed for recording membrane potential changes during vascular responses of arterioles. Perfusion of hamster cheek pouch arterioles with the dye labeled the endothelial cell layer. voltage responses from the endothelium of intact arterioles were determined by analysis of voltage-induced shifts in fluorescence emission wavelengths from dye spectra imaged from the vessel wall. Membrane depolarization caused the dye spectrum to shift toward blue wavelengths, with maximal fluorescence changes near 560 and 620 nm. In isolated nonperfused arterioles, comparison of continuous dual-wavelength recordings with simultaneous microelectrode recordings showed that the ratio of fluorescence intensities (fluorescence at 620 nm to fluorescence at 560 nm) accurately followed changes in membrane potential (6-21 mV) during vasoconstriction. The dye response was linear with respect to potential changes from -56 to -6 mV, with a voltage sensitivity of 9.7% change in the ratio per 100 mV. Membrane potential responses from in vitro and in vivo arterioles after potassium stimulation consisted of rapid ( < 0.5 -s) depolarization followed by slow repolarization over several seconds. Potassium-induced depolarizations were conducted along arterioles, and the values of the electrical length constant for conducted depolarization determined by optical and microelectrode methods were in agreement. We conclude that ratio analysis of di-8-ANEPPS fluorescence emission can be used to accurately record membrane potential changes on the time scale of seconds during vasomotor activity from arterioles.