CEREBROVASCULAR DYSFUNCTION AND DEPRESSIVE SYMPTOMS IN PRE-CLINICAL MODELS: INSIGHTS FROM A SCOPING REVIEW

While existing literature supports associations between cerebrovascular dysfunction and the emergence of depression and depressive symptoms, relatively little is known about underlying mechanistic pathways that may explain potential relationships. As such, an integrated understanding of these relationships in pre-clinical models could provide insight into the nature of the relationship, basic mechanistic linkages and areas in which additional investment should be targeted. This scoping review was conducted in MEDLINE, EMBASE and Scopus to outline the relationship between depressive symptoms and cerebrovascular dysfunction in pre-clinical animal models with additional focus on the areas above. From 3438 articles initially identified, 15 studies met the inclusion criteria and were included in the review. All studies reported a positive association between the severity of markers for cerebrovascular dysfunction and that for depressive symptoms in rodent models and this spanned all models for either pathology. Specific mechanistic links between the two such as chronic inflammation, elevated vascular oxidant stress, and altered serotonergic signaling were highlighted. Notably, almost all studies addressed outcomes in male animals, with a near complete lack of data from females, and there was little consistency in terms of how cerebrovascular dysfunction was assessed. Across nearly all studies was a lack of clarity for any "cause and effect" relationship between depressive symptoms and cerebrovascular dysfunction. At this time, it is reasonable to conclude that a correlative relationship clearly exists between the two and future investigation will be required to parse out more specific aspects to this relationship.

Application of a novel index for understanding vascular health following pharmacological intervention in a pre-clinical model of metabolic disease

While a thorough understanding of microvascular function in health and how it becomes compromised with progression of disease risk is critical for developing effective therapeutic interventions, our ability to accurately assess the beneficial impact of pharmacological interventions to improve outcomes is vital. Here we introduce a novel Vascular Health Index (VHI) that allows for simultaneous assessment of changes to vascular reactivity/endothelial function, vascular wall mechanics and microvessel density within cerebral and skeletal muscle vascular networks with progression of metabolic disease in obese Zucker rats (OZR); under control conditions and following pharmacological interventions of clinical relevance. Outcomes are compared to "healthy" conditions in lean Zucker rats. We detail the calculation of vascular health index, full assessments of validity, and describe progressive changes to vascular health index over the development of metabolic disease in obese Zucker rats. Further, we detail the improvement to cerebral and skeletal muscle vascular health index following chronic treatment of obese Zucker rats with anti-hypertensive (15%-52% for skeletal muscle vascular health index; 12%-48% for cerebral vascular health index; p < 0.05 for both), anti-dyslipidemic (13%-48% for skeletal muscle vascular health index; p < 0.05), anti-diabetic (12%-32% for cerebral vascular health index; p < 0.05) and anti-oxidant/inflammation (41%-64% for skeletal muscle vascular health index; 29%-42% for cerebral vascular health index; p < 0.05 for both) drugs. The results present the effectiveness of mechanistically diverse interventions to improve cerebral or skeletal muscle vascular health index in obese Zucker rats and provide insight into the superiority of some pharmacological agents despite similar effectiveness in terms of impact on intended targets. In addition, we demonstrate the utility of including a wider, more integrative approach to the study of microvasculopathy under settings of elevated disease risk and following pharmacological intervention. A major benefit of integrating vascular health index is an increased understanding of the development, timing and efficacy of interventions through greater insight into integrated microvascular function in combination with individual, higher resolution metrics.

Assessments of Perfusion, Blood Flow, and Vascular Structure in Ambulatory Subjects: Guidance for Translational Research Scientists

Research involving human subjects in ambulatory settings is a critical link in the chain comprising translational research, spanning preclinical research to human subject and patient cohort studies. There are presently a wide array of techniques and approaches available to investigators wishing to study blood flow, perfusion, and vascular structure and function in human subjects. In this multi-sectioned review, we discuss capillaroscopy, carotid intima-media thickness, flow-mediated dilation, laser Doppler flowmetry, near-infrared spectroscopy, peripheral arterial tonometry, pulse wave velocity, retinal fundus imaging, and vascular plethysmography. Each section contains a general overview and the physical basis of the technique followed by a discussion of the procedures involved and the necessary equipment, with attention paid to specific requirements or limitations. Subsequently, we detail which aspects of vascular function can be studied with a given technique, the analytical approach to the collected data, and the appropriate application and limitation(s) to the interpretation of the data collected. Finally, a modified scoping review provides a summary of how each assessment technique has been applied in previous studies. It is anticipated that this review will provide an efficient source of information and insight for preclinical investigators seeking to add translational aspects to their research programs.

A novel vascular health index: Using data analytics and population health to facilitate mechanistic modeling of microvascular status

The study of vascular function across conditions has been an intensive area of investigation for many years. While these efforts have revealed many factors contributing to vascular health, challenges remain for integrating results across research groups, animal models, and experimental conditions to understand integrated vascular function. As such, the insights attained in clinical/population research from linking datasets, have not been fully realized in the basic sciences, thus frustrating advanced analytics and complex modeling. To achieve comparable advances, we must address the conceptual challenge of defining/measuring integrated vascular function and the technical challenge of combining data across conditions, models, and groups. Here, we describe an approach to establish and validate a composite metric of vascular function by comparing parameters of vascular function in metabolic disease (the obese Zucker rat) to the same parameters in age-matched, "healthy" conditions, resulting in a common outcome measure which we term the vascular health index (VHI). VHI allows for the integration of datasets, thus expanding sample size and permitting advanced modeling to gain insight into the development of peripheral and cerebral vascular dysfunction. Markers of vascular reactivity, vascular wall mechanics, and microvascular network density are integrated in the VHI. We provide a detailed presentation of the development of the VHI and provide multiple measures to assess face, content, criterion, and discriminant validity of the metric. Our results demonstrate how the VHI captures multiple indices of dysfunction in the skeletal muscle and cerebral vasculature with metabolic disease and provide context for an integrated understanding of vascular health under challenged conditions.

The development of peripheral microvasculopathy with chronic metabolic disease in obese Zucker rats: a retrograde emergence?

The study of peripheral vasculopathy with chronic metabolic disease is challenged by divergent contributions from spatial (the level of resolution or specific tissue being studied) and temporal origins (evolution of the developing impairments in time). Over many years of studying the development of skeletal muscle vasculopathy and its functional implications, we may be at the point of presenting an integrated conceptual model that addresses these challenges within the obese Zucker rat (OZR) model. At the early stages of metabolic disease, where systemic markers of elevated cardiovascular disease risk are present, the only evidence of vascular dysfunction is at postcapillary and collecting venules, where leukocyte adhesion/rolling is elevated with impaired venular endothelial function. As metabolic disease severity and duration increases, reduced microvessel density becomes evident as well as increased variability in microvascular hematocrit. Subsequently, hemodynamic impairments to distal arteriolar networks emerge, manifesting as increasing perfusion heterogeneity and impaired arteriolar reactivity. This retrograde "wave of dysfunction" continues, creating a condition wherein deficiencies to the distal arteriolar, capillary, and venular microcirculation stabilize and impairments to proximal arteriolar reactivity, wall mechanics, and perfusion distribution evolve. This proximal arteriolar dysfunction parallels increasing failure in fatigue resistance, hyperemic responses, and O2 uptake within self-perfused skeletal muscle. Taken together, these results present a conceptual model for the retrograde development of peripheral vasculopathy with chronic metabolic disease and provide insight into the timing and targeting of interventional strategies to improve health outcomes.NEW & NOTEWORTHY Working from an established database spanning multiple scales and times, we studied progression of peripheral microvascular dysfunction in chronic metabolic disease. The data implicate the postcapillary venular endothelium as the initiating site for vasculopathy. Indicators of dysfunction, spanning network structures, hemodynamics, vascular reactivity, and perfusion progress in an insidious retrograde manner to present as functional impairments to muscle blood flow and performance much later. The silent vasculopathy progression may provide insight into clinical treatment challenges.

Acute mesenteric ischaemia

Acute Mesenteric Ischaemia (AMI) is an uncommon vascular emergency where the diagnosis is often difficult and overlooked and delay in diagnosis results in a grave outcome. Although extravascular events like intussusception, volvulus, strangulated hernia and adhesive obstruction in neglected cases can result intestinal gangrene, this contribution will be limited to acute mesenteric ischaemia as a primary event. AMI consists of four pathologic processes (arterial thrombosis, arterial embolism, Non Occlusive Mesenteric Ischaemia (NOMI) and mesenteric venous thrombosis (MVT)) with similar clinical presentation and one potentially fatal pathological endpoint- intestinal gangrene. The clinical setting and the patient's risk profile often give the clue to the etiological process while the presentation is dominated by severe unrelenting abdominal pain out of proportion to the physical findings. The key to the successful management depends on the surgeon's ability to suspect the diagnosis, pursue appropriate investigations and institute aggressive treatment. The mortality remains high due to difficulty and delay in the diagnosis.

The Retrojugular Approach to Carotid Endarterectomy—A Safer Technique?

The conventional technique of carotid endarterectomy involves approaching the carotid sheath, anterior and medial to the internal jugular vein with division of the facial vein. Mobilisation of the ansa cervicalis and identification of the hypoglossal nerve is usually required. We describe our results of retrojugular approach in a consecutive nonrandomised cohort of 50 carotid endarterectomy patients.

Knot in the Cava—An Unusual Complication of Swan–Ganz Catheters

Complications associated with the use of the Swan-Ganz catheters including coiling and knotting of the catheter in the central venous system or in the chambers of the heart, often with disastrous consequences. We report a case of knotting of a Swan-Ganz catheter in the superior vena cava which necessitated surgical removal via the right internal jugular vein.

Bouveret's syndrome: an unusual case of pyloroduodenal obstruction

Intestinal obstruction from gall-stones is relatively infrequent. Even less frequent is the incidence of gastric outlet obstruction from gall-stones. Bouveret in 1896 described the syndrome of gastric outlet obstruction caused by gall-stone incarceration. This article reports a case of Bouveret's syndrome treated surgically by a single stage procedure.