Tag: microcirculation

Red Blood Cell Morphology Is Associated with Altered Hemorheological Properties and Fatigue in Patients with Long COVID

Simple Summary:
SARS-CoV-2 alters the properties of oxygen-carrying red blood cells (RBCs) through a possible deterioration of hemorheological properties, such as aggregation and deformability. However, long-term changes in these properties and a possible association with morphological abnormalities remain unknown. Therefore, this study aims to investigate changes in the above-mentioned RBC properties in Long-COVID (LC). Venous blood was collected from n = 30 diagnosed LC and n = 30 non-Long-COVID controls (non-LC). Hematological parameters were measured, as well as the aggregation, deformability, and morphology of the RBCs and the mechanical sensitivity index (MS), which reflects the functional capacity of RBCs to deform. The results indicate that hematological parameters were not altered in LC. However, LC showed higher overall aggregation parameters. RBC deformability was higher in LC compared to non-LC; however, MS was limited in this group. LC showed a higher percentage of RBCs with abnormal shapes, which was related to MS and to fatigue, which is considered the leading symptom of LC. It is concluded that the symptoms of LC and changes in the blood flow determining the properties of RBCs are related to the morphological changes in RBCs. Future studies should investigate the underlying causes in order to develop appropriate therapies for this relatively new disease.
Abstract:

Background: SARS-CoV-2 infection adversely affects rheological parameters, particularly red blood cell (RBC) aggregation and deformability, but whether these changes persist in patients suffering from Long-COVID (LC) and whether these changes are related to RBC morphology remain unknown.
Methods: Venous blood was collected from n = 30 diagnosed LC patients and n = 30 non-LC controls and RBC deformability, RBC aggregation, and hematological parameters were measured. In addition, RBCs were examined microscopically for morphological abnormalities. The mechanical sensitivity index (MS) was assessed in n = 15 LC and n = 15 non-LC samples.
Results: Hematological parameters did not differ between the groups. However, LC showed higher aggregation-related parameters. Although RBC deformability was higher in LC, MS, reflecting the functional capacity to deform, was limited in this group. RBCs from LC showed significantly more morphological abnormalities. The extent of morphological abnormalities correlated with MS and the FACIT-Fatigue score of the LC patients.
Conclusion: RBCs from LC show a high degree of morphological abnormalities, which might limit the blood flow determining RBC properties and also be related to fatigue symptomatology in LC. Approaches are now needed to understand the underlying cause of these alterations and to ameliorate these permanent changes.
Source: Grau M, Presche A, Krüger A-L, Bloch W, Haiduk B. Red Blood Cell Morphology Is Associated with Altered Hemorheological Properties and Fatigue in Patients with Long COVID. Biology. 2024; 13(11):948. https://doi.org/10.3390/biology13110948 https://www.mdpi.com/2079-7737/13/11/948 (Full text)

Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome

Abstract:

Background: A considerable number of patients who contracted SARS-CoV-2 are affected by persistent multi-systemic symptoms, referred to as Post-COVID Condition (PCC). Post-exertional malaise (PEM) has been recognized as one of the most frequent manifestations of PCC and is a diagnostic criterion of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Yet, its underlying pathomechanisms remain poorly elucidated.

Purpose and methods: In this review, we describe current evidence indicating that key pathophysiological features of PCC and ME/CFS are involved in physical activity-induced PEM.

Results: Upon physical activity, affected patients exhibit a reduced systemic oxygen extraction and oxidative phosphorylation capacity. Accumulating evidence suggests that these are mediated by dysfunctions in mitochondrial capacities and microcirculation that are maintained by latent immune activation, conjointly impairing peripheral bioenergetics. Aggravating deficits in tissue perfusion and oxygen utilization during activities cause exertional intolerance that are frequently accompanied by tachycardia, dyspnea, early cessation of activity and elicit downstream metabolic effects. The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.

Source: Haunhorst S, Dudziak D, Scheibenbogen C, Seifert M, Sotzny F, Finke C, Behrends U, Aden K, Schreiber S, Brockmann D, Burggraf P, Bloch W, Ellert C, Ramoji A, Popp J, Reuken P, Walter M, Stallmach A, Puta C. Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome. Infection. 2024 Sep 6. doi: 10.1007/s15010-024-02386-8. Epub ahead of print. PMID: 39240417. https://link.springer.com/article/10.1007/s15010-024-02386-8 (Full text)

Flow Clotometry: Measuring Amyloid Microclots in ME/CFS, Long COVID, and Healthy Samples with Imaging Flow Cytometry

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has received more attention since the characterization of Long COVID (LC), a condition somewhat similar in symptom presentation and, to some extent, pathophysiological mechanisms. A prominent feature of LC pathology is amyloid, fibrinolysis-resistant fibrin(ogen) fragments, termed microclots. Despite prior identification of microclots in ME/CFS, quantitative analysis has remained challenging due to the reliance on representative micrographs and software processing for estimations.

Addressing this gap, the present study uses a cell-free imaging flow cytometry approach, optimized for the quantitative analysis of Thioflavin T-stained microclots, to precisely measure microclot concentration and size distribution across ME/CFS, LC, and healthy cohorts. We refer to our cell-free flow cytometry technique for detecting microclots as ‘flow clotometry’.

We demonstrate significant microclot prevalence in ME/CFS and LC, with LC patients exhibiting the highest concentration (18- and 3-fold greater than the healthy and ME/CFS groups, respectively). This finding underscores a common pathology across both conditions, emphasizing a dysregulated coagulation system. Moreover, relating to microclot size distribution, the ME/CFS group exhibited a significantly higher prevalence across all area ranges when compared to the controls, but demonstrated a significant difference for only a single area range when compared to the LC group.

This suggests a partially overlapping microclot profile in ME/CFS relative to LC, despite the overall higher concentration in the latter. The present study paves the way for prospective clinical application that aims to efficiently detect, measure and treat microclots.

Source: Etheresia Pretorius, Massimo Nunes, Jan pretorius et al. Flow Clotometry: Measuring Amyloid Microclots in ME/CFS, Long COVID, and Healthy Samples with Imaging Flow Cytometry, 24 June 2024, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-4507472/v1] https://www.researchsquare.com/article/rs-4507472/v1 (Full text)

Microvascular Capillary and Precapillary Cardiovascular Disturbances Strongly Interact to Severely Affect Tissue Perfusion and Mitochondrial Function in ME/CFS Evolving from the Post COVID-19 Syndrome

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a frequent, debilitating and still enigmatic disease. There is a broad overlap in the symptomatology of ME/CFS and the Post-COVID Syndrome (PCS). A fraction of the PCS patients develops the full clinical picture of ME/CFS.
New observations in microvessels and blood from patients suffering from PCS have appeared and include microclots and malformed pathological blood cells. Capillary blood flow is impaired not only by pathological blood components but also by prothrombotic changes in the vascular wall, endothelial dysfunction, and expression of adhesion molecules in the capillaries. These disturbances can finally cause a low capillary flow and even capillary stasis. A low cardiac stroke volume due to hypovolemia and the inability of the capacitance vessels to adequately constrict to deliver the necessary cardiac preload generate an unfavorable low precapillary perfusion pressure.
Furthermore, a predominance of vasoconstrictor over vasodilator influences exists, in which sympathetic hyperactivity and endothelial dysfunction play a strong role, causing constriction of resistance vessels and of precapillary sphincters which leads to a fall in capillary pressure behind the sphincters. The interaction of these two precapillary cardiovascular mechanisms causing a low capillary perfusion pressure is hemodynamically highly unfavorable in the presence of a primary capillary stasis already caused by the pathological blood components and their interaction with the capillary wall, to severely impair organ perfusion.
The detrimental coincidence of the microcirculatory with the precapillary cardiovascular disturbances may constitute the key disturbance of the Post-COVID-19 syndrome and finally lead to ME/CFS in pre-disposed patients because the interaction causes a particular kind of perfusion disturbance – capillary ischemia-reperfusion – which has a high potential of causing mitochondrial dysfunction by inducing sodium- and calcium-overload in skeletal muscles. The latter in turns worsens the vascular situation by the generation of reactive oxygen species to close a vicious cycle from which the patient can hardly escape.
Source: Wirth, K.J.; Löhn, M. Microvascular Capillary and Precapillary Cardiovascular Disturbances Strongly Interact to Severely Affect Tissue Perfusion and Mitochondrial Function in ME/CFS Evolving from the Post COVID-19 Syndrome. Preprints 2023, 2023120791. https://doi.org/10.20944/preprints202312.0791.v1  https://www.preprints.org/manuscript/202312.0791/v1 (Full text available as PDF file)

Persistent endothelial dysfunction in post-COVID-19 syndrome and its associations with symptom severity and chronic inflammation

Abstract:

Background: Post-COVID-19 syndrome (PCS) is a lingering disease with ongoing symptoms such as fatigue and cognitive impairment resulting in a high impact on the daily life of patients. Understanding the pathophysiology of PCS is a public health priority, as it still poses a diagnostic and treatment challenge for physicians.

Methods: In this prospective observational cohort study, we analyzed the retinal microcirculation using Retinal Vessel Analysis (RVA) in a cohort of patients with PCS and compared it to an age- and gender-matched healthy cohort (n=41, matched out of n = 204).

Measurements and main results: PCS patients exhibit persistent endothelial dysfunction (ED), as indicated by significantly lower venular flicker-induced dilation (vmax; 3.42% ± 1.77% vs. 4.64 % ± 2.59%; p = 0.02), narrower central retinal artery equivalent (CRAE; 178.1 [167.5 – 190.2] vs. 189.1 [179.4 – 197.2], p = 0.01) and lower arteriolar-venular ratio (AVR; (0.84 [0.8 – 0.9] vs. 0.88 [0.8 – 0.9], p = 0.007). When combining AVR and vmax, predicted scores reached good ability to discriminate groups (area under the curve: 0.75). Higher PCS severity scores correlated with lower AVR (R= -0.37 p = 0.017). The association of microvascular changes with PCS severity were amplified in PCS patients exhibiting higher levels of inflammatory parameters.

Conclusion: Our results demonstrate that prolonged endothelial dysfunction is a hallmark of PCS, and impairments of the microcirculation seem to explain ongoing symptoms in patients. As potential therapies for PCS emerge, RVA parameters may become relevant as clinical biomarkers for diagnosis and therapy management.

Source: Timon Kuchler, Roman Günthner, Andrea Ribeiro et al. Persistent endothelial dysfunction in post-COVID-19 syndrome and its associations with symptom severity and chronic inflammation, 22 May 2023, PREPRINT (Version 1) available at Research Square https://doi.org/10.21203/rs.3.rs-2952588/v1 (Full text)

Pulmonary circulation abnormalities in post-acute COVID-19 syndrome: dual-energy CT angiographic findings in 79 patients

Abstract:

Objectives: To evaluate the frequency and pattern of pulmonary vascular abnormalities in the year following COVID-19.

Methods: The study population included 79 patients remaining symptomatic more than 6 months after hospitalization for SARS-CoV-2 pneumonia who had been evaluated with dual-energy CT angiography.

Results: Morphologic images showed CT features of (a) acute (2/79; 2.5%) and focal chronic (4/79; 5%) PE; and (b) residual post COVID-19 lung infiltration (67/79; 85%). Lung perfusion was abnormal in 69 patients (87.4%). Perfusion abnormalities included (a) perfusion defects of 3 types: patchy defects (n = 60; 76%); areas of non-systematized hypoperfusion (n = 27; 34.2%); and/or PE-type defects (n = 14; 17.7%) seen with (2/14) and without (12/14) endoluminal filling defects; and (b) areas of increased perfusion in 59 patients (74.9%), superimposed on ground-glass opacities (58/59) and vascular tree-in-bud (5/59). PFTs were available in 10 patients with normal perfusion and in 55 patients with abnormal perfusion. The mean values of functional variables did not differ between the two subgroups with a trend toward lower DLCO in patients with abnormal perfusion (74.8 ± 16.7% vs 85.0 ± 8.1).

Conclusion: Delayed follow-up showed CT features of acute and chronic PE but also two types of perfusion abnormalities suggestive of persistent hypercoagulability as well as unresolved/sequelae of microangiopathy.

Clinical relevance statement: Despite dramatic resolution of lung abnormalities seen during the acute phase of the disease, acute pulmonary embolism and alterations at the level of lung microcirculation can be identified in patients remaining symptomatic in the year following COVID-19.

Key points: • This study demonstrates newly developed proximal acute PE/thrombosis in the year following SARS-CoV-2 pneumonia. • Dual-energy CT lung perfusion identified perfusion defects and areas of increased iodine uptake abnormalities, suggestive of unresolved damage to lung microcirculation. • This study suggests a complementarity between HRCT and spectral imaging for proper understanding of post COVID-19 lung sequelae.

Source: Mohamed I, de Broucker V, Duhamel A, Giordano J, Ego A, Fonne N, Chenivesse C, Remy J, Remy-Jardin M. Pulmonary circulation abnormalities in post-acute COVID-19 syndrome: dual-energy CT angiographic findings in 79 patients. Eur Radiol. 2023 Apr 25:1–13. doi: 10.1007/s00330-023-09618-9. Epub ahead of print. PMID: 37145145; PMCID: PMC10129318. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10129318/ (Full text)

Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect?

Abstract:

Following COVID-19 infection, a substantial proportion of patients suffer from persistent symptoms known as Long COVID. Among the main symptoms are fatigue, cognitive dysfunction, muscle weakness and orthostatic intolerance (OI). These symptoms also occur in myalgic encephalomyelitis/chronic fatigue (ME/CFS).
OI is highly prevalent in ME/CFS and develops early during or after acute COVID-19 infection. The causes for OI are unknown and autonomic dysfunction is hypothetically assumed to be the primary cause, presumably as a consequence of neuroinflammation. Here, we propose an alternative, primary vascular mechanism as the underlying cause of OI in Long COVID.
We assume that the capacitance vessel system, which plays a key role in physiologic orthostatic regulation, becomes dysfunctional due to a disturbance of the microvessels and the vasa vasorum, which supply large parts of the wall of those large vessels. We assume that the known microcirculatory disturbance found after COVID-19 infection, resulting from endothelial dysfunction, microthrombus formation and rheological disturbances of blood cells (altered deformability ), also affects the vasa vasorum to impair the function of the capacitance vessels.
In an attempt to compensate for the vascular deficit, sympathetic activity overshoots to further worsen OI, resulting in a vicious circle that maintains OI. The resulting orthostatic stress, in turn, plays a key role in autonomic dysfunction and the pathophysiology of ME/CFS.
Source: Wirth KJ, Löhn M. Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect? Medicina. 2022; 58(12):1807. https://doi.org/10.3390/medicina58121807 https://www.mdpi.com/1648-9144/58/12/1807 (Full text)

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Post-COVID Syndrome: A Common Neuroimmune Ground?

Abstract:

A Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic disease of unknown aetiology under growing interest now in view of the increasingly recognized post-COVID syndrome as a new entity with similar clinical presentation.

We performed the first cross-sectional study of ME/CFS in community population in Russia and then described and compared some clinical and pathophysiological characteristics of ME/CFS and post-COVID syndrome as neuroimmune disorders.

Of the cohort of 76 individuals who suggested themselves suffering from ME/CFS 56 subsequently were confirmed as having CFS/ME according to ≥1 of the 4 most commonly used case definition.

Of the cohort of 14 individuals with post-COVID-19 syndrome 14 met diagnostic criteria for ME/CFS. The prevalence of clinically expressed and subclinical anxiety and depression in ME / CFS and post-COVID ME/CFS did not differ significantly from that in healthy individuals.

Severity of anxiety / depressive symptoms did not correlate with the severity of fatigue neigther in ME / CFS nor in post-COVID ME/CFS, but the positive correlation was found between the severity of fatigue and 20 other symptoms of ME / CFS related to the domains of “post-exertional exhaustion”, “immune dysfunction”, “sleep disturbances”, “dysfunction of the autonomic nervous system”, “neurological sensory / motor disorders” and “pain syndromes”.

Immunological abnormalities were identified in 12/12 patients with ME / CFS according to the results of laboratory testing.

The prevalence of postural orthostatic tachycardia assessed by the active standing test was 37.5% in ME / CFS and 75.0% in post-COVID ME/CFS (the latter was higher than in healthy controls, p = 0.02).  There was a more pronounced increase in heart rate starting from the 6th minute of the test in post-COVID ME/CFS compared with the control group.

Assessment of the functional characteristics of microcirculation by laser doppler flowmetry revealed obvious and very similar changes in ME/CFS and post-COVID ME/CFS compared to the healthy controls.  The identified pattern corresponded to the hyperemic form of microcirculation disorders, usually observed in acute inflammatory processes or in deficiency of systemic vasoconstriction influences.

Source: Ryabkova, V.A.; Gavrilova, N.Y.; Fedotkina, T.V.; Churilov, L.P.; Shoenfeld, Y. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Post-COVID Syndrome: A Common Neuroimmune Ground?. Preprints 2022, 2022090289 (doi: 10.20944/preprints202209.0289.v1) https://www.preprints.org/manuscript/202209.0289/v1 (Full study available as PDF file)

Post-COVID-19 syndrome: retinal microcirculation as a potential marker for chronic fatigue

Abstract:

Post-COVID-19 syndrome (PCS) summarizes persisting sequelae after infection with the severe-acute-respiratory-syndrome-Coronavirus-2 (SARS-CoV-2). PCS can affect patients of all covid-19 disease severities. As previous studies revealed impaired blood flow as a provoking factor for triggering PCS, it was the aim of the present study to investigate a potential association of self-reported chronic fatigue and retinal microcirculation in patients with PCS, potentially indicating an objective biomarker.

A prospective study was performed, including 201 subjects: 173 patients with PCS and 28 controls. Retinal microcirculation was visualized by OCT-Angiography (OCT-A) and quantified by the Erlangen-Angio-Tool as macula and peripapillary vessel density (VD). Chronic Fatigue (CF) was assessed with the variables ‘Bell score’, age and gender. The VD in the superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP) were analyzed considering the repetitions (12 times). Taking in account of such repetitions a mixed model was performed to detect possible differences in the least square means between different groups of analysis.

An age effect on VD was observed between patients and controls (p<0.0001). Gender analysis yielded that women with PCS showed lower VD levels in SVP compared to male patients (p=0.0015). The PCS patients showed significantly lower VD of ICP as compared to the controls (p=0.0001, [CI: 0.32; 1]). Moreover, considering PCS patients, the mixed model reveals a significant difference between chronic fatigue (CF) and without CF in VD of SVP (p=0.0033, [CI: -4.5; -0.92]). The model included age, gender and the variable ‘Bell score’, representing a subjective marker for CF. Consequently, the retinal microcirculation might be an objective biomarker in subjective-reported chronic fatigue of patients with PCS.

Source: Sarah Schlick, Marianna Lucio, Alexander Bartsch, Adam Skornia, Jakob Hoffmanns, Charlotte Szewczykowski, Thora Schröder, Franziska Raith, Lennart Rogge, Felix Heltmann, Michael Moritz, Lorenz Beitlich, Julia Schottenhamml, Martin Herrmann, Thomas Harrer, Marion Ganslmayer, Friedrich E. Kruse, Robert Lämmer, Christian Mardin, Bettina Hohberger. Post-COVID-19 syndrome: retinal microcirculation as a potential marker for chronic fatigue. medRxiv 2022.09.23.22280264; doi: https://doi.org/10.1101/2022.09.23.22280264 https://www.medrxiv.org/content/10.1101/2022.09.23.22280264v1.full-text (Full text)

Chronic Fatigue Associated with Post-COVID Syndrome versus Transient Fatigue Caused by High-Intensity Exercise: Are They Comparable in Terms of Vascular Effects?

Abstract:

Purpose: The pathophysiology of chronic fatigue associated with post-COVID syndrome is not well recognized. It is assumed that this condition is partly due to vascular dysfunction developed during an acute phase of infection. There is great demand for a diagnostic tool that is able to clinically assess post-COVID syndrome and monitor the rehabilitation process.

Patients and methods: The Flow Mediated Skin Fluorescence (FMSF) technique appears uniquely suitable for the analysis of basal microcirculatory oscillations and reactive hyperemia induced by transient ischemia. The FMSF was used to measure vascular circulation in 45 patients with post-COVID syndrome. The results were compared with those for a group of 26 amateur runners before and after high-intensity exercise as well as for a control group of 32 healthy age-matched individuals.

Results: Based on the observed changes in the NOI (Normoxia Oscillatory Index) and RHR (Reactive Hyperemia Response) parameters measured with the FMSF technique, it was found that chronic fatigue associated with post-COVID syndrome is comparable with transient fatigue caused by high-intensity exercise in terms of vascular effects, which are associated with vascular stress in the macrocirculation and microcirculation. Acute and chronic fatigue symptomatology shared similarly altered changes in the NOI and RHR parameters and both can be linked to calcium homeostasis modification.

Conclusion: The NOI and RHR parameters measured with the FMSF technique can be used for non-invasive clinical assessment of post-COVID syndrome as well as for monitoring the rehabilitation process.

Source: Chudzik M, Cender A, Mordaka R, Zielinski J, Katarzynska J, Marcinek A, Gebicki J. Chronic Fatigue Associated with Post-COVID Syndrome versus Transient Fatigue Caused by High-Intensity Exercise: Are They Comparable in Terms of Vascular Effects? Vasc Health Risk Manag. 2022 Sep 6;18:711-719. doi: 10.2147/VHRM.S371468. PMID: 36097586; PMCID: PMC9464031.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9464031/ (Full text)