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Vol. 39. Núm. 1.
Páginas 25-26 (Janeiro 2020)
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Vol. 39. Núm. 1.
Páginas 25-26 (Janeiro 2020)
Editorial comment
DOI: 10.1016/j.repc.2020.02.004
Open Access
Hemorheology, microcirculation and macrocirculation
Hemorreologia, microcirculação e macrocirculação
Carlota Saldanhaa,b
a Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
b Instituto de Medicina Molecular João Lobo Antunes, Cento Académico de Medicina de Lisboa, Lisboa, Portugal
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The article by Cekirdekci and Bugan published in this issue of the Journal1 opens up new prospects for improving our knowledge of microvascular angina (MVA).1 Clinical characterization of MVA and coronary artery disease (CAD) shows them to be examples of endothelial dysfunction at the level of the microcirculation and macrocirculation, respectively. There is now general consensus about both coronary microcirculation and macrocirculation.

The authors selected biomarkers of hemorheology and inflammation and applied clinical methodology to diagnose and classify the patients and the control group. The latter were similar to the MVA and CAD patient groups regarding the presence of other associated diseases. The statistical computation performed confirmed the value of the control group used, which in my opinion is more realistic than other control groups selected without comorbidities.

As is well known, a compromised microcirculation leads to insufficient blood perfusion in arterioles, capillaries and venules, and hence poor oxygenation in tissues and organs. One cause could be a reduced ability of erythrocytes to reversibly deform (erythrocyte deformability) when they move into capillaries with a smaller diameter than the cell. Erythrocyte deformability is a hemorheological parameter which is affected by erythrocyte membrane composition, structure, internal viscosity, and signal transduction mechanisms resulting from exogenous and/or endogenous binding or compounds entering through the erythrocyte membrane.2 A large number of disorders can change this hemorheological property of erythrocytes and hence reduce their ability to deliver oxygen to the tissue microcirculation. If such a situation is accompanied by diminished oxygen diffusion to endothelial cells, this may trigger cell hypoxia, leading to the generation of reactive oxygen species.3 In tissues where the oxygen partial pressure is lower than in the lungs, the efflux of nitric oxide (NO) from the erythrocyte through its membrane protein band4 is concomitant with oxygen delivery from the erythrocyte to cell tissues.3 In situations of abnormal microcirculation, reactive nitrogen species may be formed, leading to decreased concentrations of NO and loss of its physiological vasodilator function.3

It is important to be aware of the possible existence of an inflammatory process in post-capillary venules where decreased rolling velocity and increased leukocyte adhesion retard blood flow. The presence of erythrocyte aggregates in post-capillary venules results in leukocytes remaining near the surface of the endothelium, promoting an acute inflammatory response.5 This effect was observed by us in an animal model of acute inflammation with labeled neutrophils using intravital microscopy.5 Impaired erythrocyte deformability and decreased NO efflux from erythrocytes during the acute phase of inflammation were observed.5 As the in vivo study was performed with mice, the quantity of blood was insufficient for whole blood viscosity (WBV) assessment, but according to other studies, WBV is likely to be increased.

In addition to its function as an acute phase protein in inflammatory diseases, fibrinogen is involved in the mechanism of the coagulation cascade, the ability of erythrocytes to scavenge or donate NO, and erythrocyte aggregation.6,7

Erythrocyte aggregation and deformability are hemorheological parameters that influence WBV as a function of shear rates and hematocrit (HCT).8 In blood samples from healthy humans, when subjected to low shear rates erythrocyte aggregation takes place at higher WBV values in an HCT-dependent fashion, in contrast to erythrocyte deformability, which is increased by high shear rates and lower WBV values, and is little influenced by HCT.8

Cekirdekci and Bugan chose WBV and C-reactive protein (CRP) as hemorheological and inflammatory biomarkers, respectively, of cardiovascular disease, as has been previously demonstrated.9,10 The levels of both parameters were increased in the MVA and CAD groups, confirming the existence of inflammation in patients with CAD and suggesting the presence of a subclinical inflammatory state in patients with MVA. The present study illustrates the need for studies that include microcirculation observations. The microcirculation can be monitored non-invasively, the sublingual region being the area of choice to apply hand-held microscopy.11 In addition, assessment of NO efflux from erythrocytes obtained from patients with MVA and CAD will be helpful for monitoring the effects of drugs on the microcirculation and macrocirculation, respectively. Our team observed that NO efflux from erythrocytes of patients with systemic lupus erythematosus and rheumatoid arthritis is negatively associated with both intima-media thickness (IMT) and the presence of atherosclerosis plaques, and is an independent predictor of carotid IMT.12

Systemic inflammation occurs in both the macrocirculation and the microcirculation, and endothelial dysfunction in resistance coronary vessels contributes to coronary microvascular disease and vice versa.13 Before the achievement of this consensus we found that disturbances in microcirculation in the eye are associated with endothelial dysfunction in patients suffering from macrocirculatory diseases such as the accelerated phase of hypertension.14

The authors of the present article pointed out the need to quantify WBV by specialized equipment rather than through a formula based on a mathematical model.

WBV is a hemorheological parameter dependent on erythrocyte aggregation and deformability, as well as on plasma viscosity, and not only hematocrit. The intricacies of the vascular network, with variations in vessel length and diameter and number of ramifications, have implications for the differing values of HCT. All hemorheological parameters can be determined in appropriate laboratories with specialized equipment, which will help provide a better understanding of the pathophysiology. Follow-up studies conducted in patients with acute myocardial infarction demonstrated that patients with lower erythrocyte aggregation and CRP values at hospital discharge present higher recurrent event and mortality rates than patients with normal values.15

The development of new hemorheological microfluidic devices to be used at the bedside16 and microcirculatory apparatus means that MVA and CAD patients can be subdivided according to the associated pathology, and as well as WBV and HCT, erythrocyte deformability and aggregation, NO efflux from erythrocytes and microcirculatory parameters can be assessed. In the near future, new questions will be asked that will lead to multiple scientific discoveries.

Conflicts of interest

The author has no conflicts of interest to declare.

I.E. Cekirdekci, B. Bugan.
Whole blood viscosity in microvascular angina and coronary artery disease: significance and feasibility.
Rev Port Cardiol, 39 (2020), pp. 15-21
J.P. Lopes de Almeida, S. de Oliveira, C. Saldanha.
Erythrocyte as a biological sensor.
Clin Hemorheol Microcirc, 51 (2012), pp. 1-20
A.S. Silva-Herdade, G. Andolina, C. Faggi, et al.
Erythrocyte deformability – a partner of the inflammatory response.
Microvasc Res, 107 (2016), pp. 34-38
N.N. Barvitenko, M. Aslam, J. Filosa, et al.
Tissue oxygen demand in regulation of the behavior of the cells in the vasculature.
Microcirculation, 20 (2013), pp. 484-501
C. Saldanha.
Physiological role of erythrocyte nitric oxide.
Clin Hemorheol Microcirc, 64 (2016), pp. 517-520
C. Saldanha, A.S. Silva-Herdade.
Chapter 3. Fibrinogen involvement in hemorheology and inflammation.
pp. 115-146
P. Lane, S. Gross.
Hemoglobin as a chariot for NO bioactivity.
Nat Med, 8 (2002), pp. 657-658
B. Coull, N. Beamer, P. De Garmo, et al.
Chronic blood hyperviscosity in subjects with acute stroke, transient ischemic attack, and risk factors for stroke.
Stroke, 22 (1991), pp. 162-168
O. Baskurt, H.J. Meiselman.
In vivo hemorheology.
Handbook of hemorheology and hemodynamics, pp. 322-338
L. Sargento, C. Saldanha, J. Monteiro, et al.
Evidence of prolonged disturbances in the haemostatic, hemorheologic and inflammatory profiles in transmural myocardial infarction survivors.
Thromb Haemost, 89 (2003), pp. 892-903
E.C. Boerma, K.R. Mathura, P.H. van der Voort, et al.
Quantifying bedside-derived imaging of microcirculatory abnormalities in septic patients: a prospective validation study.
Crit Care, 9 (2005), pp. 601-606
M.J. Santos, L.M. Pedro, H. Canhão, et al.
Hemorheological parameters are related to subclinical atherosclerosis in systemic lupus erythematosus and rheumatoid arthritis patients.
Atherosclerosis, 219 (2011), pp. 821-826
H.A. Struijker Boudier, G.M. Cohuet, M. Baumann, et al.
The heart, macrocirculation and microcirculation in hypertension: a unifying hypothesis.
J Hypertens Suppl, 21 (2003), pp. S19-S23
J.B. Nogueira, A. Freitas, C. Moreira, et al.
Hypertension in an accelerated phase. Cardiologic, ophthalmologic and hemorrheologic study.
Rev Port Cardiol, 7 (1988), pp. 305-318
L. Sargento, C. Saldanha, J. Monteiro, et al.
Long-term prognostic value of protein C activity, erythrocyte aggregation and membrane fluidity in transmural myocardial infarction.
Thromb Haemost, 94 (2005), pp. 380-388
Y.J. Kang.
Microfluidic-based technique for measuring RBC aggregation and blood viscosity in a continuous and simultaneous fashion.
Micromachines (Basel), 9 (2018), pp. E467
Copyright © 2020. Sociedade Portuguesa de Cardiologia
Revista Portuguesa de Cardiologia

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