Early microvascular modifications in patients previously hospitalized for COVID-19: comparison with healthy individuals

Background SARS-CoV2 infection has been associated to a wide range of clinical scenarios, named COVID-19, ranging from acute respiratory distress syndrome to blood coagulation abnormalities and vascular manifestations related to hyper-inflammation. Recent focus has been addressed to study of microvascular alterations which may explain COVID-19 pathophysiology. Alterations in microvascular structure, identified as increased wall to lumen ratio (WLR) of retinal arterioles, have been extensively described in patients with cardiovascular diseases, such as hypertension or diabetes mellitus. Both inflammation and immune system dysregulation seem to play a role in the pathogenesis of these morphological changes. Purpose Aim of this study was to evaluate through Adaptive Optics microvascular differences of retinal arterioles between patients experienced COVID-19 and controls. Methods Patients were hospitalized between 28th February and 15th April at a Internal Medicine ward in a tertiary care hospital. All patients tested positive for a SARS-CoV-2 nasopharyngeal swab at admission and showed signs of pneumonia and respiratory insufficiency. Adaptive Optics, which allows a non-invasive evaluation of retinal arteriole structure, and blood chemistry exams were performed as part of follow up visits between 2 to 3 months after hospitalization. Baseline characteristics were collected through medical records. COVID-19 patients were compared to age- and sex-matched healthy subjects referred to our center between 2018 and 2019. Results A total of 80 patients were included in this study (of which 40 were COVID-19 patients). Apart from smoking habit, other baseline characteristics (sex, age, cardiovascular risk factors and main comorbidities) did not differ between the two groups. At follow up visit COVID-19 patients showed lower values for leukocytes (6.2 vs. 7.5x103/μL, p=0.015) and lymphocytes (1.9 vs. 2.8x103/μL, p=0.002). Creatinine values were higher in patients who suffered from COVID-19 (1.0 vs 0.8 mg/dl, p=0.004 – Figure 1, panel A). Adaptive Optics showed no differences in terms of internal lumen, wall thickness and WLR of retinal arterioles. However, the wall cross-sectional area (WCSA) was found to be higher in COVID-19 patients (p=0.039 – Figure 1, panel B). Hypertension significantly affected both WCSA and WLR between COVID-19 and healthy individuals, while diabetes only impacted on WLR (Figure 2). Conclusion Previous studies described the presence of leukopenia and lymphopenia during the acute phase of SARS-CoV2 infection. Our study demonstrates that these alterations persist several weeks after symptoms onset. Adaptive Optics showed microvascular alterations occurring in these patients: in particular, higher wall cross-sectional area of retinal arterioles were observed in patients after COVID-19 hospitalization, reflecting the complex pathogenic mechanisms which may explain the wide range of symptoms and clinical severity. FUNDunding Acknowledgement Type of funding sources: None. Figure 1 Figure 2

PREVALENCE, PATHOGENESIS, CLASSIFICATION, IMAGING, SCREENING AND MANAGE-MENT OF DIABETIC RETINOPATHY- A CRITICAL REVIEW

Diabetic retinopathy is that the leading reason for sightlessness among people between twenty-five and seventyfour years older within the industrialised world. Diabetes mellitus (DM) includes a heterogeneous cluster of disorders of carbohydrate, protein, and metastasis manifesting hyperglycemia. Diabetic retinopathy could be microangiopathy ensuing from the chronic effects of the disease, and shares similarities with the microvascular alterations that occur in different tissues at risk of DM equivalent to the kidneys and also the peripheral nerves. Diabetic retinopathy is assessed into nonproliferative and proliferative stages. Nonproliferative diabetic retinopathy (NPDR) involves progressive intraretinal microvascular alterations that may result in, and a lot of advanced proliferative stages outlined by extraretinal neovascularization. Imaging modalities in common clinical use for the management of NPDR and DME embrace structure photography, fluorescein angiography (FA), and optical coherence tomography (OCT). The suggested schedule for screening and surveillance for NPDR reflects data concerning the epidemiology and natural history of the disease. Diabetic retinopathy could be a leading explanationfor vision loss in working-age Americans and a major cause of sightlessness worldwide. The International Diabetes Federation estimates that as several as 592 million individuals worldwide can have DM in 2035, a rise from or so 387 million people calculable to possess the disease in 2014. Here, we tend to present a review of the presentunderstanding and new insights into biochemical mechanisms within the pathological process in DR, classification, furthermore as clinical treatments for DR patients. Keywords: Diabetic retinopathy, diabetes mellitus, retinal degeneration, fluoresces in angiography, optical coher- ence tomography, VEGF, focal/grid laser photocoagulation.

Increased Hepatic Microvascular Density, Oxygenation, and VEGF in the Hypertrophic Lobe following Portal Vein Embolization in Rabbits

<b><i>Introduction:</i></b> The microvascular events following portal vein embolization (PVE) are poorly understood despite the pivotal role of the microcirculation in liver regeneration and tumor progression. We aimed to assess the changes in hepatic microvascular perfusion and neo-angiogenesis after experimental PVE. <b><i>Methods:</i></b> PVE of the cranial liver lobes was performed in 12 New Zealand White rabbits divided into 2 groups of permanent (P-PVE) and reversible PVE (R-PVE), respectively. Hepatobiliary scintigraphy and CT were used to evaluate hepatic function and volume. Hepatic microcirculation was assessed using a handheld vital microscope (Cytocam) to measure microvascular density (total vessel density; TVD) before PVE, right after PVE, and 20 min after PVE, as well as at 14 days (D14 post-PVE) and 35 days (D35 post-PVE). Additionally, on D35, microvascular PO₂ and liver parenchymal VEGF were assessed. <b><i>Results:</i></b> Eleven rabbits were included after PVE (R-PVE, <i>n</i> = 5; P-PVE, <i>n</i> = 6). TVD in the nonembo­lized (hypertrophic) lobes was higher than in the embolized (atrophic) lobes of the P-PVE group at D35 post-PVE (36.7 ± 7.2 vs. 23.4 ± 4.9 mm/mm²; <i>p</i> &#x3c; 0.05). In the R-PVE group, TVD in the nonembolized lobes was not increased at D35. Function and volume were increased in the nonembolized lobes of the P-PVE group compared to the embolized lobes, but not in the R-PVE group. Likewise, the mmicrovascular PO₂ and VEGF staining rate were higher in the nonembolized lobes of the P-PVE group at D35 post-PVE. <b><i>Discussion/Conclusion:</i></b> Successful volumetric and functional hypertrophy of the nonembolized lobe was accompanied by microvascular alterations featuring increased neo-angiogenesis, microvascular density, and microvascular oxygen pressure following P-PVE.

Foveal Remodeling of Retinal Microvasculature in Parkinson’s Disease

BackgroundRetinal microvascular alterations have been previously described in Parkinson’s disease (PD) patients using optical coherence tomography angiography (OCT-A). However, an extensive description of retinal vascular morphological features, their association with PD-related clinical variables and their potential use as diagnostic biomarkers has not been explored.MethodsWe performed a cross-sectional study including 49 PD patients (87 eyes) and 40 controls (73 eyes). Retinal microvasculature was evaluated with Spectralis OCT-A and cognitive status with Montreal Cognitive Assessment. Unified PD Rating Scale and disease duration were recorded in patients. We extracted microvascular parameters from superficial and deep vascular plexuses of the macula, including the area and circularity of foveal avascular zone (FAZ), skeleton density, perfusion density, vessel perimeter index, vessel mean diameter, fractal dimension (FD) and lacunarity using Python and MATLAB. We compared the microvascular parameters between groups and explored their association with thickness of macular layers and clinical outcomes. Data were analyzed with General Estimating Equations (GEE) and adjusted for age, sex, and hypertension. Logistic regression GEE models were fitted to predict diagnosis of PD versus controls from microvascular, demographic, and clinical data. The discrimination ability of models was tested with receiver operating characteristic curves.ResultsFAZ area was significantly smaller in patients compared to controls in superficial and deep plexuses, whereas perfusion density, skeleton density, FD and lacunarity of capillaries were increased in the foveal zone of PD. In the parafovea, microvascular parameters of superficial plexus were associated with ganglion cell-inner plexiform layer thickness, but this was mainly driven by PD with mild cognitive impairment. No such associations were observed in controls. FAZ area was negatively associated with cognition in PD (non-adjusted models). Foveal lacunarity, combined with demographic and clinical confounding factors, yielded an outstanding diagnostic accuracy for discriminating PD patients from controls.ConclusionParkinson’s disease patients displayed foveal microvascular alterations causing an enlargement of the vascular bed surrounding FAZ. Parafoveal microvascular alterations were less pronounced but were related to inner retinal layer thinning. Retinal microvascular abnormalities helped discriminating PD from controls. All this supports OCT-A as a potential non-invasive biomarker to reveal vascular pathophysiology and improve diagnostic accuracy in PD.