Arterial stiffness is strongly and negatively associated with the total volume of red blood cells

Acute regulation of erythropoietin via lower body negative pressure: Influence of sex and age

The regulation of erythropoiesis via hemodynamic stimuli such as reduced central blood volume (CBV) remains uncertain in women and elderly individuals. This study assessed the acute effects of lower body negative pressure (LBNP) on key endocrine biomarkers regulating erythropoiesis, that is, erythropoietin (EPO) and copeptin, in young and older women and men (n = 87). Transthoracic echocardiography and hemodynamics were assessed throughout incremental LBNP levels for 1 hour, or until presyncope, with established methods. Venous blood samples were collected at baseline and immediately after termination of the orthostatic tolerance (OT) test for subsequent hormone analyses. The average age of young women and men (33.1 ± 6.0 vs. 29.5 ± 6.9 yr) and older women and men (63.8 ± 8.0 vs. 65.3 ± 8.9 yr) as well as their physical activity levels were matched within each age and sex group. CBV, as determined by right atrial volume, was reduced in all individuals at the end of the OT test (p < 0.001). The average OT time ranged from 50.1 to 58.1 min in all individuals. LBNP increased circulating EPO in young women (p = 0.023) but not in young men or older individuals. Copeptin was increased in all individuals with LBNP but was exclusively associated with EPO in men (r = 0.39, p = 0.013). The present study indicates that the acute hemodynamic regulation of EPO production is both sex- and age-dependent.

Aortic Stiffness: A Major Risk Factor for Multimorbidity in the Elderly

Multimorbidity, the coexistence of multiple health conditions in an individual, has emerged as one of the greatest challenges facing health services, and this crisis is partly driven by the aging population. Aging is associated with increased aortic stiffness (AoStiff), which in turn is linked with several morbidities frequently affecting and having disastrous consequences for the elderly. These include hypertension, ischemic heart disease, heart failure, atrial fibrillation, chronic kidney disease, anemia, ischemic stroke, and dementia. Two or more of these disorders (multimorbidity) often coexist in the same elderly patient and the specific multimorbidity pattern depends on several factors including sex, ethnicity, common morbidity routes, morbidity interactions, and genomics. Regular exercise, salt restriction, statins in patients at high atherosclerotic risk, and stringent blood pressure control are interventions that delay progression of AoStiff and most likely decrease multimorbidity in the elderly.

Differences in Cardiac Output and Aerobic Capacity Between Sexes Are Explained by Blood Volume and Oxygen Carrying Capacity

Whether average sex differences in cardiorespiratory fitness can be mainly explained by blood inequalities in the healthy circulatory system remains unresolved. This study evaluated the contribution of blood volume (BV) and oxygen (O₂) carrying capacity to the sex gap in cardiac and aerobic capacities in healthy young individuals. Healthy young women and men (n = 28, age range = 20–43 years) were matched by age and physical activity. Echocardiography, blood pressures, and O₂ uptake were measured during incremental exercise. Left ventricular end-diastolic volume (LVEDV), stroke volume (SV), cardiac output (Q), peak O₂ uptake (VO_2peak), and BV were assessed with precise methods. The test was repeated in men after blood withdrawal and reduction of O₂ carrying capacity, reaching women’s levels. Before blood normalization, exercise cardiac volumes and output (LVEDV, SV, Q) adjusted by body size and VO_2peak (42 ± 9 vs. 50 ± 11 ml⋅min^–1⋅kg^–1, P < 0.05) were lower in women relative to men. Blood normalization abolished sex differences in cardiac volumes and output during exercise (P ≥ 0.100). Likewise, VO_2peak was similar between women and men after blood normalization (42 ± 9 vs. 40 ± 8 ml⋅min^–1⋅kg^–1, P = 0.416). In conclusion, sex differences in cardiac output and aerobic capacity are not present in experimental conditions matching BV and O₂ carrying capacity between healthy young women and men.

Sex Differences in Orthostatic Tolerance Are Mainly Explained by Blood Volume and Oxygen Carrying Capacity

Supplemental Digital Content is available in the text.

The reduced orthostatic tolerance (OT) that is characteristic of the female sex may be explained by multiple phenotypic differences between sexes. This study aimed to elucidate the mechanistic role of blood volume (BV) and oxygen carrying capacity on sex differences in OT.

Sex and age interaction in fundamental circulatory volumetric variables at peak working capacity

Background

Whether the fundamental hematological and cardiac variables determining cardiorespiratory fitness and their intrinsic relationships are modulated by major constitutional factors, such as sex and age remains unresolved.

Methods

Transthoracic echocardiography, central hemodynamics and pulmonary oxygen (O₂) uptake were assessed in controlled conditions during submaximal and peak exercise (cycle ergometry) in 85 healthy young (20–44 year) and older (50–77) women and men matched by age-status and moderate-to-vigorous physical activity (MVPA) levels. Main outcomes such as peak left ventricular end-diastolic volume (LVEDV_peak), stroke volume (SV_peak), cardiac output (Q_peak) and O₂ uptake (VO_2peak), as well as blood volume (BV), BV–LVEDV_peak and LVEDV_peak–SV_peak relationships were determined with established methods.

Results

All individuals were non-smokers and non-obese, and MVPA levels were similar between sex and age groups (P ≥ 0.140). BV per kg of body weight did not differ between sexes (P ≥ 0.118), but was reduced with older age in men (P = 0.018). Key cardiac parameters normalized by body size (LVEDV_peak, SV_peak, Q_peak) were decreased in women compared with men irrespective of age (P ≤ 0.046). Older age per se curtailed Q_peak (P ≤ 0.022) due to lower heart rate (P < 0.001). In parallel, VO_2peak was reduced with older age in both sexes (P < 0.001). The analysis of fundamental circulatory relationships revealed that older women require a higher BV for a given LVEDV_peak than older men (P = 0.024).

Conclusions

Sex and age interact on the crucial circulatory relationship between total circulating BV and peak cardiac filling, with older women necessitating more BV to fill the exercising heart than age- and physical activity-matched men.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-021-00409-9.

Hemoglobin and erythrocyte count are independently and positively associated with arterial stiffness in a community-based study

The association of blood hemoglobin (Hb) concentration and red blood cell (RBC) count with arterial stiffness is not well-defined. Herein, we examined the associations of brachial-ankle pulse wave velocity (baPWV) and augmentation index (AI) with Hb level and RBC count from a population cohort in and around Beijing, China. A total of 3994 participants (57.1 ± 8.8 years old) were included in our analysis. Blood routine examination, baPWV, and possible covariates were examined. The mean Hb, RBC count, AI corrected for a heart rate of 75 bpm (AIP75), and baPWV were 131.4 ± 17.1 g/l, 4.2 ± 0.5 10¹²/l, 80.2 ± 12.0%, and 1665.3 ± 377.1 cm/s, respectively, consistent with previously described cohorts. RBC counts and Hb levels were positively associated with baPWV (β for 10¹²/l RBC: 50.08 cm/s, 95% confidence interval [CI]: 30.54-69.63, p < 0.001; β for 10 g/l Hb: 9.05 cm/s, 95% CI: 3.35-14.76, p = 0.002) and AIP75 (β for 10¹²/l RBC: 1.33%, 95% CI: 0.55-2.12, p < 0.001; β for 10 g/l Hb: 0.34%, 95% CI: 0.12-0.57, p = 0.003), despite adjustment for covariates. The average levels of baPWV in the third-fourth quartile RBC groups were higher than in the first quartile (Q1) group (p < 0.001 for all). The average levels of baPWV in the fourth quartile Hb groups were higher than in the Q1 Hb group (p = 0.038). Mean AIP75 levels in the third-fourth RBC and Hb groups were higher than in the Q1 groups (p < 0.05 for all). In conclusion, circulating blood Hb levels and RBC counts are positively associated with arterial stiffness in our community-based study.

Relationship between plasma volume and essential blood constituents in patients with heart failure and preserved ejection fraction

INTRODUCTION

Notwithstanding recent progress on molecular mechanisms underlying heart failure with preserved ejection fraction (HFpEF), multiple pathophysiological aspects of this condition including the basis of anaemia and other haematological disorders remain unresolved. In this study, we sought to determine the relationship of plasma volume (PV), a plausible confounding factor for the concentration of solutes in blood, with key haematological markers in HFpEF patients.

METHODS

Total circulating PV was determined with high precision, automated carbon monoxide rebreathing in 24 stable HFpEF patients (70 ± 8 years, left ventricular ejection fraction = 55±5%) and 18 healthy age- and sex-matched control (HC) individuals. Linear regression analyses were performed to determine the association of PV with a comprehensive set of haematological variables.

RESULTS

Haematocrit (40·1 ± 4·9 versus 43·6 ± 2·7%, P = 0·004) and haemoglobin concentration (131 ± 16 versus 142 ± 7 g l^-1 , P = 0·003) were reduced in HFpEF patients compared with HC individuals. In regression analyses, PV was negatively associated with haematocrit (r = -0·45, P = 0·029) and haemoglobin concentration (r = -0·44, P = 0·030) in HFpEF patients, whereas these variables were not associated with PV in HC individuals (P≥0·198). Regarding blood electrolytes, PV was negatively associated with K⁺ (r = -0·43, P = 0·036) and Ca²⁺ (r = -0·44, P = 0·032) in HFpEF patients but not in HC individuals (P≥0·734). None of the above associations were detected in HFpEF patients when using ideal instead of measured PV.

CONCLUSION

The blood concentration of routine markers of anaemia and electrolyte balance is specifically and linearly associated with PV in HFpEF patients. Excess or deficit of circulating PV may confound clinical diagnosis in this population.

Effects of hemodialysis on blood volume, macro- and microvascular function

BACKGROUND

Vascular dysfunction is considered to spur the progression of cardiovascular disease in hemodialysis (HD) patients. Whether the HD procedure itself contributes to vascular dysfunction remains incompletely investigated. The present study sought to comprehensively assess the effects of HD on arterial and venous function along with concomitant changes in blood volume (BV).

METHODS AND RESULTS

We determined BV with high-precision, automated carbon monoxide-rebreathing, arterial stiffness using applanation tonometry and intrinsic microvascular function via retinal vessel analysis prior to and after conventional 4-hour HD in fasting-controlled conditions in 10 patients. All HD patients were non-smokers and non-obese (body mass index = 22.8 ± 2.8 m·kg^-2). Hypertension (70%), coronary artery disease (40%) and diabetes mellitus (20%) were the most prevalent comorbidities. Prior to HD, all patients presented with hypervolemia (+2208 ± 1213 ml). HD decreased body weight (-1.72 ± 1.25 kg, P = 0.002) and plasma volume (-689 ± 566 ml, P = 0.004), while hematocrit (Hct) was concomitantly increased (+4.8 ± 4.5%, P = 0.009). HD did not affect large elastic artery stiffness, as determined by carotid-femoral pulse wave velocity (P = 0.448) and carotid distensibility (P = 0.562). In contrast, flicker light-induced retinal venular dilation was reduced by three-fourths after HD (-2.4 ± 1.7%, P = 0.039), in parallel to increased retinal venular diameter (+11.2 ± 4.9 μm, P = 0.002). In regression analyses, a negative association was observed between HD-induced changes in Hct and retinal venular dilation (r ≥ -0.89, P ≤ 0.045).

CONCLUSION

Conventional HD resulting in substantial plasma volume removal do not alter large artery elastic properties, whereas intrinsic microvascular venular dilator function is markedly impaired, an effect directly associated with the increase in hemoconcentration.

The role of blood volume in cardiac dysfunction and reduced exercise tolerance in patients with diabetes

Blood volume is an integral component of the cardiovascular system, and fundamental to discerning the pathophysiology of multiple cardiovascular conditions leading to exercise intolerance. Based on a systematic search of controlled studies assessing blood volume, in this Personal View we describe how hypovolaemia is a prevalent characteristic of patients with diabetes, irrespective of sex, age, and physical activity levels. Multiple endocrine and haematological mechanisms contribute to hypovolaemia in diabetes. The regulation of intravascular volumes is altered by sustained hyperglycaemia and hypertension. Chronic activation of endocrine systems controlling fluid homeostasis, such as the renin-angiotensin-aldosterone system and vasopressin axis, has a role in progressive kidney desensitisation and diabetic nephropathy. Furthermore, albumin loss from the intravascular compartment reduces the osmotic potential of plasma to retain water. Hypovolaemia also affects the loading conditions and filling of the heart in diabetes. The elucidation of modifiable volumetric traits will plausibly have major health benefits in the diabetes population.

Age-dependent impairment of the erythropoietin response to reduced central venous pressure in HFpEF patients

Despite growing research interest in the pathophysiology of heart failure with preserved ejection fraction (HFpEF), it remains unknown whether central hemodynamic alterations inherently present in this condition do affect blood pressure and blood volume (BV) regulation. The present study sought to determine hemodynamic and endocrine responses to prolonged orthostatic stress in HFpEF patients. Central venous pressure (CVP) assessed via the internal jugular vein (IJV) aspect ratio with ultrasonography, arterial pressure and heart rate were determined at supine rest and during 2 hours of moderate (25-30°) head-up tilt (HUT) in 18 stable HFpEF patients (71.2 ± 7.3 years), 14 elderly (EC), and 10 young (YC) healthy controls. Parallel endocrine measurements comprised main BV-regulating hormones: pro-atrial natriuretic peptide, copeptin, aldosterone, and erythropoietin (EPO). At supine rest, the IJV aspect ratio was higher (>30%) in HFpEF patients compared with EC and YC, while mean arterial pressure was elevated in HFpEF patients (98.0 ± 13.1 mm Hg) and EC (95.6 ± 8.3 mm Hg) versus YC (87.3 ± 5.0 mm Hg) (P < 0.05). HUT increased heart rate (+10%) and reduced the IJV aspect ratio (-52%), with similar hemodynamic effects in all groups (P for interaction ≥ 0.322). The analysis of endocrine responses to HUT revealed a group×time interaction for circulating EPO, which was increased in YC (+10%) but remained unaltered in HFpEF patients and EC. The EPO response to a given reduction in CVP is similarly impaired in HFpEF patients and elderly controls, suggesting an age-dependent dissociation of EPO production from hemodynamic regulation in the HFpEF condition.

Red blood cell volume is not decreased in ESA-naive anemic chronic kidney disease patients

Anemia is defined according to decreased blood hemoglobin concentration ([Hb]), which is considered a marker of low total red blood cell volume (RBCV). Alterations of plasma volume (PV) may also modify [Hb] without concomitant changes in RBCV. Since anemia and fluid retention are frequent complications of chronic kidney disease (CKD), we hypothesized that anemia during CKD may in part be related to expanded PV without a simultaneous decrease in RBCV. We quantified hemoglobin mass, RBCV, PV, and total blood volume (BV) using an automated carbon monoxide device in 40 consecutive stage 3-5 CKD patients not on dialysis and in seven healthy male controls of the same age range. These were compared within and to predicted volumes according to Nadler's formula. Arterial stiffness and NT-proBNP were measured. RBCV was similar to predicted values range in anemic CKD patients 2073 (1818-2704) versus, 2061 (1725-2473) mL, P > 0.05. In contrast, PV was largely increased in anemic CKD patients (3881 (3212-4352) vs. 2916 (2851-3201)), P = 0.01. Of 26 anemic patients, only six had a >20% decrease in RBCV as the cause for their anemia, whereas 14 had a >20% increase of PV as a cause for their anemia. NT-pro BNP correlated with eGFR but neither with PV nor BV, whereas arterial stiffness was not correlated to blood volumes. Anemia in CKD as diagnosed by low [Hb] is not necessarily associated to low RBCV but may reflect increased PV. This finding has implications for the treatment of CKD patients and may refrain from normalizing [Hb] levels in all CKD patients.

Effect of Exercise on Arterial Stiffness: Is There a Ceiling Effect?

BACKGROUND

Whether arterial stiffness (AS) can be improved by regular exercise in healthy individuals remains equivocal according to cross-sectional and longitudinal studies assessing arterial properties at discrete time points. The purpose of the present study was to pinpoint the time course of training-induced adaptations in central AS.

METHODS

Aorta characteristic impedance (Zc) and carotid distensibility (CD) were determined with ultrasonography prior to (week 0) and across 8 weeks (weeks 2, 4, and 8) of supervised endurance training (ET) (3 × 60 minutes cycle ergometry sessions per week), in 9 previously untrained healthy normotensive adults (27 ± 4 years) with no history of cardiovascular disease. Exercise capacity was assessed by maximal oxygen consumption (VO2max) elicited by incremental ergometry.

RESULTS

VO2max increased throughout the ET intervention (+12% from week 0 to week 8, P < 0.001, P for linear trend <0.001). Systolic blood pressure rose with ET (+7% from week 0 to week 8, P = 0.019, P for linear trend <0.001). Aorta Zc augmented from week 0 to week 8 of ET in all individuals (+38%, P = 0.003, P for linear trend = 0.002). CD did not significantly differ among time points (P = 0.196) although a linear decreasing trend was detected (P = 0.016).

CONCLUSIONS

Central AS augments during a conventional ET intervention that effectively enhances aerobic exercise capacity in young individuals. This suggests that normal, healthy elastic arteries are not amendable to improvement unless impairment is present.

True Anemia―Red Blood Cell Volume Deficit―in Heart Failure

Background—

Anemia in heart failure (HF) is commonly diagnosed according to hemoglobin concentration [Hb], hence may be the result of hemodilution or true red blood cell volume (RBCV) deficit. Whether true (nonhemodilutional) anemia in HF can or cannot be generally inferred by [Hb] measurements and clinical correlates remains unclear. The purpose of this study was to systematically review the literature and investigate the status and correlates of RBCV in patients with HF.

Methods and Results—

MEDLINE, Scopus, and Web of Science were searched since their inceptions until April 2016 for articles directly reporting or allowing the calculation of intravascular volumes (RBCV, plasma volume) in patients with HF according to the International Council for Standardization in Hematology. Eighteen studies were included after systematic review, comprising a total of 368 patients with HF (limits for mean age=49–80 years, sex=0%–92% females, left ventricular ejection fraction=26%–61%). Mean RBCV was reduced (limits=67%–88% of normal) in all studies including HF patients with anemia (low [Hb]) (7 studies, n=127), whereas only 2 of 10 studies in nonanemic patients with HF presented lower than normal mean RBCV (90% and 96%). In metaregression analyses, RBCV was positively associated with [Hb] ( B =6.10, SE=1.44) and negatively associated with age ( B =−1.14, SE=0.23), % females ( B =−0.38, SE=0.04), left ventricular ejection fraction ( B =−0.81, SE=0.20), and body mass index ( B =−3.55, SE=0.46; P <0.001).

Conclusions—

Presence or absence of true anemia in patients with HF as determined by RBCV status mainly concurs with diagnosis based on [Hb] and presents negative relationships with age, female sex, left ventricular ejection fraction, and body mass index.

Arterial stiffness in hematologic malignancies

Malignant and cardiovascular disorders are the top causes of mortality worldwide. This article reviews the main literature data and mechanisms linking hematologic malignancies and arterial stiffness, focusing on recent experimental and clinical results. Several links were found in hematologic malignancies between complete blood count and arterial stiffness. Chemotherapy, especially anthracyclines, cyclophosphamide and tyrosine kinase inhibitors, as well as radiotherapy and hematopoietic stem cell transplantation are the main known causes of arterial stiffness increase in hematologic malignancies. The mechanisms of arterial stiffness elevation in hematologic malignancies include an increased oxidative stress, impaired vascular wall homeostasis, endothelial dysfunction and apoptosis of endothelial cells, overexpression of inflammatory cytokines, accelerated atherosclerosis, increased blood viscosity and unstable platelet aggregates. Guidelines regarding cardiovascular health screening and cardiovascular risk scores are necessary for hematologic cancer survivors in order to improve prognosis and quality of life of the patients.