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JACC. Cardiovascular Imaging Aug 2019
Topics: Humans; Microcirculation; Percutaneous Coronary Intervention; ST Elevation Myocardial Infarction
PubMed: 31395247
DOI: 10.1016/j.jcmg.2019.06.008 -
Experimental Physiology Sep 2020What is the topic of this review? We describe a range of techniques in the time, frequency and information domains and their application alone and together for the... (Review)
Review
NEW FINDINGS
What is the topic of this review? We describe a range of techniques in the time, frequency and information domains and their application alone and together for the analysis of blood flux signals acquired using laser Doppler fluximetry. What advances does it highlight? This review highlights the idea of using quantitative measures in different domains and scales to gain a better mechanistic understanding of the complex behaviours in the microcirculation.
ABSTRACT
To date, time- and frequency-domain metrics of signals acquired through laser Doppler fluximetry have been unable to provide consistent and robust measures of the changes that occur in the microcirculation in healthy individuals at rest or in response to a provocation, or in patient cohorts. Recent studies have shown that in many disease states, such as metabolic and cardiovascular disease, there appears to be a reduction in the adaptive capabilities of the microvascular network and a consequent reduction in physiological information content. Here, we introduce non-linear measures for assessing the information content of fluximetry signals and demonstrate how they can yield deeper understanding of network behaviour. In addition, we show how these methods may be adapted to accommodate the multiple time scales modulating blood flow and how they can be used in combination with time- and frequency-domain metrics to discriminate more effectively between the different mechanistic influences on network properties.
Topics: Humans; Laser-Doppler Flowmetry; Microcirculation; Microvessels; Regional Blood Flow; Skin
PubMed: 31875329
DOI: 10.1113/EP087874 -
Acta Anaesthesiologica Scandinavica Aug 2020The Revised (or "Extended") Starling principle is based on highly controlled laboratory-based frog and rodent experiments and remains a hypothesis awaiting clinical... (Review)
Review
The Revised (or "Extended") Starling principle is based on highly controlled laboratory-based frog and rodent experiments and remains a hypothesis awaiting clinical validation. A key point is that the endothelial glycocalyx layer moves the oncotic gradient from being between the plasma and the interstitium to between the plasma and a virtually protein-free space between the glycocalyx and the endothelial cell membrane, which dramatically changes the prerequisites for fluid absorption from tissue to plasma. However, many experimental and clinical observations in humans agree poorly with the new microcirculatory proposals. The most troubling aspect of the explanation regarding the role of the glycocalyx in the Revised Starling principle is the effective reabsorption of fluid by skeletal muscle when the capillary filtration pressure is acutely reduced. Other issues include the plasma volume effects of hypertonic saline, iso-oncotic and hyper-oncotic albumin, fluid distribution during cardio-pulmonary bypass, and the virtually identical capillary leakage of plasma and albumin despite marked inflammation found in our fluid therapy studies. The Revised Starling principle deals mainly with steady-state conditions, but the circulatory system is highly dynamic. Second to second vasomotion is always operational and must be considered to understand what we observe in humans.
Topics: Capillary Permeability; Endothelium, Vascular; Fluid Therapy; Glycocalyx; Humans; Microcirculation; Reproducibility of Results
PubMed: 32270471
DOI: 10.1111/aas.13593 -
International Journal of Molecular... Dec 2014The microcirculation is a portion of the vascular circulatory system that consists of resistance arteries, arterioles, capillaries and venules. It is the place where... (Review)
Review
The microcirculation is a portion of the vascular circulatory system that consists of resistance arteries, arterioles, capillaries and venules. It is the place where gases and nutrients are exchanged between blood and tissues. In addition the microcirculation is the major contributor to blood flow resistance and consequently to regulation of blood pressure. Therefore, structural remodeling of this section of the vascular tree has profound implications on cardiovascular pathophysiology. This review is focused on the role that reactive oxygen species (ROS) play on changing the structural characteristics of vessels within the microcirculation. Particular attention is given to the resistance arteries and the functional pathways that are affected by ROS in these vessels and subsequently induce vascular remodeling. The primary sources of ROS in the microcirculation are identified and the effects of ROS on other microcirculatory remodeling phenomena such as rarefaction and collateralization are briefly reviewed.
Topics: Animals; Humans; Microcirculation; Microvessels; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Neovascularization, Pathologic; Neovascularization, Physiologic; Reactive Oxygen Species
PubMed: 25535075
DOI: 10.3390/ijms151223792 -
Medicina (Kaunas, Lithuania) Dec 2023Coronary microvascular dysfunction (CMD) is a clinical entity linked with various risk factors that significantly affect cardiac morbidity and mortality. Hypertension,... (Review)
Review
Coronary microvascular dysfunction (CMD) is a clinical entity linked with various risk factors that significantly affect cardiac morbidity and mortality. Hypertension, one of the most important, causes both functional and structural alterations in the microvasculature, promoting the occurrence and progression of microvascular angina. Endothelial dysfunction and capillary rarefaction play the most significant role in the development of CMD among patients with hypertension. CMD is also related to several hypertension-induced morphological and functional changes in the myocardium in the subclinical and early clinical stages, including left ventricular hypertrophy, interstitial myocardial fibrosis, and diastolic dysfunction. This indicates the fact that CMD, especially if associated with hypertension, is a subclinical marker of end-organ damage and heart failure, particularly that with preserved ejection fraction. This is why it is important to search for microvascular angina in every patient with hypertension and chest pain not associated with obstructive coronary artery disease. Several highly sensitive and specific non-invasive and invasive diagnostic modalities have been developed to evaluate the presence and severity of CMD and also to investigate and guide the treatment of additional complications that can affect further prognosis. This comprehensive review provides insight into the main pathophysiological mechanisms of CMD in hypertensive patients, offering an integrated diagnostic approach as well as an overview of currently available therapeutical modalities.
Topics: Humans; Microvascular Angina; Coronary Circulation; Myocardial Ischemia; Coronary Artery Disease; Hypertension; Cardiomyopathies; Microcirculation; Coronary Vessels
PubMed: 38138252
DOI: 10.3390/medicina59122149 -
The Journal of Heart and Lung... Sep 2023Reduced arterial pulsatility in continuous-flow left ventricular assist devices (CF-LVAD) patients has been implicated in clinical complications. Consequently, recent...
BACKGROUND
Reduced arterial pulsatility in continuous-flow left ventricular assist devices (CF-LVAD) patients has been implicated in clinical complications. Consequently, recent improvements in clinical outcomes have been attributed to the "artificial pulse" technology inherent to the HeartMate3 (HM3) LVAD. However, the effect of the "artificial pulse" on arterial flow, transmission of pulsatility into the microcirculation and its association with LVAD pump parameters is not known.
METHODS
The local flow oscillation (pulsatility index, PI) of common carotid arteries (CCAs), middle cerebral arteries (MCAs) and central retinal arteries (CRAs-representing the microcirculation) were quantified by 2D-aligned, angle-corrected Doppler ultrasound in 148 participants: healthy controls, n = 32; heart failure (HF), n = 43; HeartMate II (HMII), n = 32; HM3, n = 41.
RESULTS
In HM3 patients, 2D-Doppler PI in beats with "artificial pulse" and beats with "continuous-flow" was similar to that of HMII patients across the macro- and microcirculation. Additionally, peak systolic velocity did not differ between HM3 and HMII patients. Transmission of PI into the microcirculation was higher in both HM3 (during the beats with "artificial pulse") and in HMII patients compared with HF patients. LVAD pump speed was inversely associated with microvascular PI in HMII and HM3 (HMII, r = 0.51, p < 0.0001; HM3 "continuous-flow," r = 0.32, p = 0.0009; HM3 "artificial pulse," r = 0.23, p = 0.007), while LVAD pump PI was only associated with microcirculatory PI in HMII patients.
CONCLUSIONS
The "artificial pulse" of the HM3 is detectable in the macro- and microcirculation but without creating a significant alteration in PI compared with HMII patients. Increased transmission of pulsatility and the association between pump speed and PI in the microcirculation indicate that the future clinical care of HM3 patients may involve individualized pump settings according to the microcirculatory PI in specific end-organs.
Topics: Humans; Microcirculation; Heart-Assist Devices; Heart Failure; Heart Rate; Middle Cerebral Artery
PubMed: 37098374
DOI: 10.1016/j.healun.2023.04.002 -
Revista Brasileira de Terapia Intensiva 2017Parameters related to macrocirculation, such as the mean arterial pressure, central venous pressure, cardiac output, mixed venous saturation and central oxygen... (Review)
Review
Parameters related to macrocirculation, such as the mean arterial pressure, central venous pressure, cardiac output, mixed venous saturation and central oxygen saturation, are commonly used in the hemodynamic assessment of critically ill patients. However, several studies have shown that there is a dissociation between these parameters and the state of microcirculation in this group of patients. Techniques that allow direct viewing of the microcirculation are not completely disseminated, nor are they incorporated into the clinical management of patients in shock. The numerous techniques developed for microcirculation assessment include clinical assessment (e.g., peripheral perfusion index and temperature gradient), laser Doppler flowmetry, tissue oxygen assessment electrodes, videomicroscopy (orthogonal polarization spectral imaging, sidestream dark field imaging or incident dark field illumination) and near infrared spectroscopy. In the near future, the monitoring and optimization of tissue perfusion by direct viewing and microcirculation assessment may become a goal to be achieved in the hemodynamic resuscitation of critically ill patients.
Topics: Critical Illness; Hemodynamics; Humans; Microcirculation; Monitoring, Physiologic; Point-of-Care Systems; Resuscitation
PubMed: 28977264
DOI: 10.5935/0103-507X.20170033 -
Pharmacology & Therapeutics Jan 2023Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the... (Review)
Review
Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.
Topics: Humans; Endothelial Progenitor Cells; Microcirculation; Signal Transduction; Cell Differentiation; Sepsis
PubMed: 36436689
DOI: 10.1016/j.pharmthera.2022.108315 -
Microcirculation (New York, N.Y. : 1994) Feb 2016This Special Topic Issue is concerned with the mechanisms that determine the structure of microvascular networks. The vast number of vessels and the highly plastic...
This Special Topic Issue is concerned with the mechanisms that determine the structure of microvascular networks. The vast number of vessels and the highly plastic character of the microcirculation give evidence that microvascular network structures emerge as a result of responses of individual vessels and cells to the local stimuli that they experience, through a combination of angiogenesis, remodeling and pruning. The articles in this issue of Microcirculation address a range of cellular and molecular mechanisms involved in these processes.
Topics: Animals; Humans; Microcirculation; Neovascularization, Physiologic; Vascular Diseases
PubMed: 26639099
DOI: 10.1111/micc.12262 -
Microcirculation (New York, N.Y. : 1994) Jan 2018Arterial tone is tightly regulated by a variety of potassium (K ) permeable ion channels at the sarcolemma of vascular smooth muscle cells. In particular, several types...
Arterial tone is tightly regulated by a variety of potassium (K ) permeable ion channels at the sarcolemma of vascular smooth muscle cells. In particular, several types of K channels provide a significant hyperpolarizing influence and serve to oppose pressure and agonist-induced membrane depolarization to promote smooth muscle relaxation and augmentation of vascular diameter and blood flow. In recent years, a number of studies have underscored previously unknown roles for particular K subunits, new modes of channel regulation, and distinct cellular functions for these channels during physiological and pathological conditions. In this overview, we highlight articles contained in this Special Topics Issue that focus on the latest, most exciting advancements in the field of K channels in the microcirculation. The collection of articles aims to highlight important new discoveries and controversies in the field of vascular K channels as well as to shed light on key questions that require additional investigation.
Topics: Animals; Humans; Microcirculation; Muscle, Smooth, Vascular; Potassium Channels, Voltage-Gated
PubMed: 29239491
DOI: 10.1111/micc.12435