Hormonal Control of Blood Viscosity.

The hemodynamic milieu differs throughout the vascular tree because of varying vascular geometry and blood velocities. Accordingly, the risk of turbulence, which is dictated by the Reynolds and Dean numbers, also varies. Relatively high blood viscosity is needed to prevent turbulence in the left ventricle and aorta, where high-velocity blood changes direction several times. Low blood viscosity is needed in the capillaries, where erythrocytes pass through vessels with a diameter smaller than their own. In addition, higher blood viscosity is necessary when the cardiac output and peak blood velocity increase as a part of a sympathetic response or anemia, which occurs following significant hemorrhage. Blood viscosity, as reflected in systemic vascular resistance and vascular wall shear stress, is sensed, respectively, by cardiomyocyte stretching in the left ventricle and mechanoreceptors for wall shear stress in the carotid sinus. By controlling blood volume and red blood cell mass, the renin-aldosterone-angiotensin system and the systemic vascular resistance response control the hematocrit, the strongest intrinsic determinant of blood viscosity. These responses provide gross control of blood viscosity. Fine-tuning of blood viscosity in transient conditions is provided by hormonal control of erythrocyte deformability. The short half-life of some of these hormones limits their activity to specific vascular beds. Hormones that modulate blood viscosity include erythropoietin, angiotensin II, brain natriuretic factor, epinephrine, prostacyclin E2, antidiuretic hormone, and nitric oxide.

New Onset Anemia, Worsened Plasma Creatinine Concentration, and Hyperviscosity in a Patient With a Monoclonal IgM Paraprotein.

A 76-year-old female followed closely for five years with IgM monoclonal gammopathy of uncertain significance developed anemia, worsened plasma creatinine concentration, and markedly elevated serum viscosity. This case illustrates the scope of pathology that can be caused by elevated blood viscosity. Our patient's anemia was a homeostatic response to normalize systemic vascular resistance and resulted from activation of the systemic vascular resistance response. The elevated plasma creatinine resulted from decreased renal perfusion because of elevated blood viscosity. Recent insights in hemorheology (the study of blood flow) are discussed, namely the recent identification of preferential blood flow patterns and erythrocyte autoregulation of deformability. These insights confirm that blood viscosity is part of the "milieu intérieur."

Defining Insights.

BACKGROUND: Insights, when acted upon, can result in positive changes to the business, for HCPs, and ultimately for patients. Medical Information, as a customer facing function, is one of the groups that generate insights. Data and insights across different functions of an organization need to be compiled to provide a comprehensive view. The purpose of this paper is to develop a shared definition of insights and to provide a working guidance for the insight process. METHODS: Two surveys were conducted of the phactMI membership first to establish a shared definition of insights and then to benchmark current insight process. From this data and the shared experience of the working group a proposed guidance was developed. RESULTS: The developed definition of an insight is "An insight is the deeper understanding of the why behind trends of information that lead us to determine if an action is warranted". For the most robust outcomes, insight identification needs to be a cross functional activity. The proposed structured approach can be leveraged and customized for any organization and include the following five steps: INvestigate, Scrutinize, Identify, Take Action, and Enlighten (INSITE). CONCLUSION: The INSITE process provides a simple framework that should become routine for all Medical Information colleagues who are leading the work around insights. The process should be shared across all functions that participate in the insight generation process. This is another area where Medical Information can demonstrate leadership and highlight their value to the organization.

COVID-19 Demonstrates That Inflammation Is a Hyperviscous State.

Many of the complications of severe coronavirus disease-2019 (COVID-19) are caused by blood hyperviscosity driven by marked hyperfibrinogenemia. This results in a distinctive hyperviscosity syndrome which affects areas of high and low shear. A change in blood viscosity causes a threefold inverse change in blood flow, which increases the risk of thrombosis in both arteries and veins despite prophylactic anticoagulation. Increased blood viscosity decreases perfusion of all tissues, including the lungs, heart, and brain. Decreased perfusion of the lungs causes global ventilation-perfusion mismatch which results in silent hypoxemia and decreased efficacy of positive pressure ventilation in treating pulmonary failure in COVID-19. Increased blood viscosity causes a mismatch in oxygen supply and demand in the heart, resulting in myocarditis and ventricular diastolic dysfunction. Decreased perfusion of the brain causes demyelination because of a sublethal cell injury to oligodendrocytes. Hyperviscosity can cause stasis in capillaries, which can cause endothelial necrosis. This can lead to the rarefaction of capillary beds, which is noted in "long-COVID." The genome of the virus which causes COVID-19, severe acute respiratory syndrome coronavirus 2, contains an extraordinarily high number of the oligonucleotide virulence factor 5'-purine-uridine-uridine-purine-uridine-3', which binds to toll-like receptor 8, hyperactivating innate immunity. This can lead to a marked elevation in fibrinogen levels and an increased prevalence of neutrophil extracellular traps in pulmonary failure, as seen in COVID-19 patients.

PurUUpurU: An Oligonucleotide Virulence Factor in RNA Viruses.

Background The copy number of the oligonucleotide 5'-purine-uridine-uridine-purine-uridine-3' (purUUpurU) motif in a viral genome was previously shown to correlate with the severity of acute illness. This study aimed to determine whether purUUpurU content correlates with virulence in other single-strand RNA (ssRNA) viruses that vary in clinical severity. Methodology We determined the copy number of purUUpurU in the genomes of two subtypes of human respiratory syncytial virus (RSV), respiratory syncytial virus A (RSV-A), and respiratory syncytial virus B (RSV-B), which vary in clinical severity. In addition, we determined the purUUpurU content of the four ebolaviruses that cause human disease, dengue virus, rabies virus, human rhinovirus-A, poliovirus type 1, astrovirus, rubella, yellow fever virus, and measles virus. Viral nucleotide sequence files were downloaded from the National Center for Biotechnology Information (NCBI)/National Institutes of Health website. In addition, we determined the cumulative case fatality rate of 20 epidemics of the Ebola virus and compared it with that of the other human ebolaviruses. Results The genomic purUUpurU content correlated with the severity of acute illness caused by both subtypes of RSV and human ebolaviruses. The lowest purUUpurU content was in the genome of the rubella virus, which causes mild disease. Conclusions The quantity of genomic purUUpurU is a virulence factor in ssRNA viruses. Blood hyperviscosity is one mechanism by which purUUpurU causes pathology. Comparative quantitative genomic analysis for purUUpurU will be helpful in estimating the risk posed by emergent ssRNA viruses.

From the Oligonucleotide purUUpurU to Cytokine Storm, Elevated Blood Viscosity, and Complications of Coronavirus Disease 2019.

Background Coronavirus disease 2019 (COVID-19) can be associated with pathologic inflammation. The authors hypothesize that a high copy number of a purine-uridine-rich nucleotide motif is present in the genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hyperactivates innate immunity. Methods The number of purine-uridine-uridine-purine-uridine (purUUpurU) motifs was counted in the genomes of SARS-CoV-2 and other single-strand RNA viruses. The nucleotides of SARS-CoV-2 in random order were used as a control. Results PurUUpurU occurred 2.8 times more often in the actual SARS-CoV-2 genome than the randomized genome. The number of purUUpurU motifs correlates with the potential severity of acute illness caused by these viruses, except for influenza A. Conclusion The large number of purUUpurU in SARS-CoV-2 may hyperactivate innate immunity, potentially causing the markedly increased concentrations of cytokines, acute phase reactants, and blood viscosity that can be seen in COVID-19.

The Role of Blood Viscosity in Infectious Diseases.

Blood viscosity is increased by elevated concentrations of acute phase reactants and hypergammaglobulinemia in inflammation. These increase blood viscosity by increasing plasma viscosity and fostering erythrocyte aggregation. Blood viscosity is also increased by decreased erythrocyte deformability, as occurs in malaria. Increased blood viscosity contributes to the association of acute infections with myocardial infarction (MI), venous thrombosis, and venous thromboembolism. It also increases vascular resistance, which decreases tissue perfusion and activates stretch receptors in the left ventricle, thereby initiating the systemic vascular resistance response. This compensates for the increased vascular resistance by vasodilation, lowering hematocrit, and decreasing intravascular volume. This physiological response causes the anemias associated with malaria, chronic inflammation, and other chronic diseases. Since tissue perfusion is inversely proportional to blood viscosity, anemia may be beneficial as it increases tissue perfusion when erythrocyte aggregating factors or erythrocytes with decreased deformability are present in the blood.

Apolipoprotein(a) is the Product of a Pseudogene: Implications for the Pathophysiology of Lipoprotein(a).

Apolipoprotein(a) [apo(a)] is an apolipoprotein unique to lipoprotein(a) [Lp(a)]. Although it has no known function, Lp(a) is a risk factor for accelerated atherothrombosis. We hypothesize that LPA, the gene which encodes apo(a), is a heretofore unrecognized unprocessed pseudogene created by duplication of PLG, the gene which encodes plasminogen. Unprocessed pseudogenes are genes which were created by duplication of functional genes and subsequently lost function after acquiring various mutations. This hypothesis explains many of the unusual features of Lp(a) and apo(a). Also, this hypothesis has implications for the therapy of elevated Lp(a) and atherothrombosis theory. Because apo(a) is functionless, the diseases associated with elevated levels of Lp(a) are due to its impact on blood viscosity.

Flawed Reasoning Allows the Persistence of Mainstream Atherothrombosis Theory.

Deaths due to atherothrombosis are increasing throughout the world except in the lowest socio-demographic stratum. This is despite 60 years of study and expenditure of billions of dollars on lipid theory. Nevertheless, mainstream atherothrombosis theory persists even though it has failed numerous tests. Contrary data are ignored, consistent with the practice of science as envisioned by Thomas Kuhn. This paper examines defects in mainstream atherogenesis theory and the flawed logic which allows its persistence in the face of what should be obvious shortcomings.

Perspective: interesterified triglycerides, the recent increase in deaths from heart disease, and elevated blood viscosity.

The authors hypothesize that consumption of interesterified fats may be the cause of the continuous increase in cardiovascular deaths in the United States which began in 2011. Interesterification is a method of producing solid fats from vegetable oil and began to supplant partial hydrogenation for this purpose upon recognition of the danger of trans fats to cardiovascular health. Long, straight carbon chains, as are present in saturated and trans fatty acids, decrease the fluidity of the erythrocyte cell membrane, which decreases erythrocyte deformability and increases blood viscosity. This decrease in cell membrane fluidity is caused by increased van der Waals interactions, which also solidify dietary fats. Elevated blood viscosity is favored as the pathogenic mechanism by which trans fats increase cardiovascular mortality because changes in lipoprotein levels do not account for all the mortality attributable to their consumption. The rapid changes in cardiovascular mortality noted with the introduction and withdrawal of trans fats from the food supply are reviewed. The evidence implicating elevated blood viscosity in cardiovascular disease is also reviewed. Data regarding the production and consumption of interesterified fats in the US should be released in order to determine if there is an association with the observed increase in cardiovascular deaths.

Atherothrombosis is a Thrombotic, not Inflammatory Disease.

The authors hypothesize that thrombosis causes both the complications of atherosclerosis as well as the underlying lesion, the atherosclerotic plaque, which develops from the organization of mural thrombi. These form in areas of slow blood flow, which develop because of flow separation created by changing vascular geometry and elevated blood viscosity. Many phenomena typically ascribed to inflammation or "chronic oxidative stress", such as the development of fatty streaks, "endothelial dysfunction," "vulnerable plaques," and the association of mild elevations of C-reactive protein and cytokines with atherothrombosis are better explained by hemorheologic and hemodynamic abnormalities, particularly elevated blood viscosity. Elevated blood viscosity decreases the perfusion of skeletal muscle, leading to myocyte expression of the myokine IL-6, decreased glucose uptake, insulin resistance, hyperglycemia, and metabolic syndrome. The hyperfibrinogenemia and hypergammaglobulinemia present in true inflammatory diseases foster atherothrombosis by increasing blood viscosity.

Uric acid increases erythrocyte aggregation: Implications for cardiovascular disease.

Uric acid may be a risk factor for atherosclerotic cardiovascular disease, although the data conflict and the mechanism by which it may cause cardiovascular disease is uncertain. This study was performed to test the hypothesis that uric acid, an anion at physiologic pH, can cause erythrocyte aggregation, which itself is associated with cardiovascular disease. Normal erythrocytes and erythrocytes with a positive direct antiglobulin test for surface IgG were incubated for 15 minutes in 14.8 mg/dL uric acid. Erythrocytes without added uric acid were used as controls. Erythrocytes were then examined microscopically for aggregation. Aggregates of up to 30 erythrocytes were noted when normal erythrocytes were incubated in uric acid. Larger aggregates were noted when erythrocytes with surface IgG were incubated in uric acid. Aggregation was negligible in controls. These data show that uric acid causes erythrocyte aggregation. The most likely mechanism is decreased erythrocyte zeta potential. Erythrocyte aggregates will increase blood viscosity at low shear rates and increase the risk of atherothrombosis. In this manner, hyperuricemia and decreased zeta potential may be risk factors for atherosclerotic cardiovascular disease.

The systemic vascular resistance response: a cardiovascular response modulating blood viscosity with implications for primary hypertension and certain anemias.

Without an active regulatory feedback loop, increased blood viscosity could lead to a vicious cycle of ischemia, increased erythropoiesis, further increases of blood viscosity, decreased tissue perfusion with worsened ischemia, further increases in red cell mass, etc. We suggest that an increase in blood viscosity is detected by mechanoreceptors in the left ventricle which upregulate expression of cardiac natriuretic peptides and soluble erythropoietin receptor. This response normalizes systemic vascular resistance and blood viscosity at the cost of producing 'anemia of chronic disease or inflammation' or 'hemolytic anemia' both of which are better described as states of compensated hyperviscosity. Besides its role in disease, this response is also active in the physiologic adaptation to chronic exercise. Malfunction of this response may cause primary hypertension.

The role of chronic hyperviscosity in vascular disease.

The pathogenesis of several major cardiovascular diseases, including atherosclerosis, hypertension, and the metabolic syndrome, is not widely understood because the role of blood viscosity is overlooked. Low-density lipoprotein accelerates atherosclerosis by increasing blood viscosity in areas of low flow or shear, predisposing to thrombosis. Atherosclerotic plaques are organized mural thrombi, as proposed by Duguid in the mid-twentieth century. High-density lipoprotein protects against atherosclerosis by decreasing blood viscosity in those areas. Blood viscosity, at the least, contributes to hypertension by increasing systemic vascular resistance. Because flow is inversely proportional to viscosity, hyperviscosity decreases perfusion and glucose utilization by skeletal muscle, contributing to hyperglycemia in the metabolic syndrome. Therapeutic phlebotomy reduces blood pressure and serum glucose levels in the metabolic syndrome by improving blood viscosity.