Young athletes under pressure?

Regular participation in exercise has long been known to result in cardiovascular adaptation. Historically, the ‘athlete’s heart’ hypothesis has encouraged a dichotomised view of the heart’s adaptation to sport, depending on whether the physical activity was either of isotonic activity (runners and swimmers) resulting in ‘cardiomegaly’ or of isometric effort (wrestlers and shot putters, ie, ‘strength’ athletes) with clear peripheral adaptations and an ‘obvious increase in cardiac size’. Today, the classification of sports according to their physiological demands acknowledges a greater diversity of exposure, depending on the physical activity, with an emphasis on a ‘graded transition’ between the main categories: dynamic, static and impact. Still, our understanding of the determinants of structural and functional cardiovascular adaptation to exercise are limited, and the consequences for health remain a matter of debate

CrossTalk proposal: Blood flow pulsatility in left ventricular assist device patients is essential to maintain normal brain physiology

For the first time in history, some humans live without a palpable pulse (Purohit et al. 2018). This remarkable physiology is the consequence of surgical implantation of a continuous‐flow left ventricular assist device (CF‐LVAD) in patients with end‐stage heart failure. Blood flow produced by CF‐LVADs has a low oscillatory profile in the aorta that results in significantly reduced pulsatility in all arterial compartments (Castagna et al. 2017; Fig. 1). Despite remarkable gains in quality of life and longevity, complications that affect not only morbidity, such as gastrointestinal bleeding, but also mortality, such as strokes, are still prevalent in CF‐LVAD patients. Low pulsatility has been proposed as a major culprit in contributing to these adverse events (Mancini & Colombo, 2015; Goldstein et al. 2018). In this CrossTalk proposal, we present the current arguments in favour of maintaining an appropriate amount of arterial pulsatility, in particular in the cerebral circulation, to lower risk in these patients

“Bionic Women and Men”: The Unique Physiology of Left Ventricular Assist Device Patients – Keep your finger on the pulse!

Across many countries in the world, advanced heart failure patients who are eligible for a heart transplant face the same dilemma: there are not enough donor hearts available for all. The current next-best alternative to a heart transplant is the surgical implantation of a left ventricular assist device (LVAD). Although the purpose of the LVAD is to relieve the overloaded left ventricle of heart failure patients and restore a normal cardiac output, patients have presented with high levels of stroke gastrointestinal bleeding and right-heart failure. One potential reason for this increased risk is the continuous flow of the implanted LVAD. As a result, the majority of LVAD patients do not have a palpable pulse (Purohit et al., 2018), creating a unique arterial biology in these humans (Castagna et al., 2017). Perhaps surprising is the superior health outcome of patients supported with continuous-flow (CF) compared with pulsatile-flow LVADs. In addition, the reduced/absent pulsatility in these CF-LVAD patients (see figure 1.) enables the investigation of unique arterial physiology and cardiovascular regulation, which has already revealed some unexpected observations. For example, continuous-flow patients appear to have a higher sympathetic activity (Cornwell et al., 2015), and suffer complications above a low systolic blood pressure of ~100 mmHg, atypical of non-LVAD populations in whom hypertension (>140 mmHg) is a predictor of stroke (Pinsino et al., 2019). Thus, the medical debate whether continuous flow is truly better for the health of advanced heart failure patients also necessitates a more generic, fundamental discussion into ‘normal’ arterial physiology & health. The comprehensive study investigating the detailed cardiovascular response and adaptations to drastically altered haemodynamics in heart failure, with and without LVAD support, at rest, during physical activity and in combination with cardiovascular acting medication, is essential. This unique area of research presents an opportunity to significantly increase our fundamental physiological understanding of the interaction between cardiac dynamics (volume, force, ejection pattern) and arterial regulation (flow, blood pressure, sympathetic activity, endothelial function, pulsatility). Therefore, the symposium entitled “Bionic women and men – Physiology lessons from implantable cardiac devices” held at the 2019 Annual Meeting of The Physiological Society in Aberdeen, UK, brought together clinicians and scientists from a previous CrossTalk debate (Cornwell et al., 2019; Stöhr et al., 2019) to review the current knowledge of LVAD patients and identify outstanding questions in the field. In total, four presentations were given and each of them have been published as symposium reports in this edition of Experimental Physiology

Biosecurity on poultry farms from on-farm fluidized bed combustion and energy recovery from poultry litter

peer-reviewedThe spreading of poultry litter in recent years has led to a serious increase in levels of eutrophication, nitrate leaching, high Biological Oxygen Demand (BOD), ammonia toxicity, high chlorine concentrations and pathogen contamination. The review presented here details the optimum standards that should be met when storing litter for On-Farm Fluidized Bed Combustion. Storage conditions are paramount to a fuel combusting to its highest possible potential. Safety measures such as the prevention of leaching and spontaneous combustion must be adhered to, so too should the prevention and containment of possible diseases and pathogens to minimize the effects of contamination

Carotid artery wall mechanics in young males with high cardiorespiratory fitness

The influence of cardiorespiratory fitness (CRF) on arterial stiffness in young adults remains equivocal. Beyond conventional measures of arterial stiffness, 2D strain imaging of the common carotid artery (CCA) provides novel information related to the intrinsic properties of the arterial wall. Therefore, this study aimed to assess the effect of CRF on both conventional indices of CCA stiffness and 2D strain parameters, at rest and following a bout of aerobic exercise in young healthy males. Short‐axis ultrasound images of the CCA were recorded in 34 healthy men [22 years (95%CI, 19–22)] before, and immediately after 5‐minutes of aerobic exercise (40% VO2max). Images were analysed for arterial diameter, peak circumferential strain (PCS), and peak systolic and diastolic strain rates (S‐SR, D‐SR). Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP) were simultaneously assessed and Petersons' elastic modulus (Ep) and Beta stiffness (β1) were calculated. Participants were separated post hoc into moderate and high fitness groups [VO2max: 48.9 ml.kg‐1 min‐1 (95%CI, 44.7–53.2) vs. 65.6 ml.kg‐1 min‐1 (95%CI, 63.1–68.1); P 0.13) but were elevated in the moderate‐fitness group post‐exercise (P 0.05). High‐fit individuals exhibit elevated CCA PCS and S‐SR, which may reflect training‐induced adaptations that help to buffer the rise in pulse‐pressure and stroke volume during exercise

“Bionic Women and Men” Part 1: Cardiovascular Lessons from Heart Failure Patients Implanted with Left Ventricular Assist Devices (LVADs)

Some humans with chronic, advanced heart failure are surgically implanted with a left ventricular assist device (LVAD). Because the LVAD produces a continuous flow, a palpable pulse is often absent in these patients. This allows for a unique investigation of the human circulation and has created a controversy around the ‘need’ for a pulse. The medical debate has also generated a more generic, fundamental discussion into what is ‘normal’ arterial physiology and health. The comprehensive study and understanding of the arterial responses to drastically altered haemodynamics due to continuous‐flow LVADs, at rest and during activity, presents an opportunity to significantly increase our current understanding of the fundamental components of arterial regulation (flow, blood pressure, sympathetic activity, endothelial function, pulsatility) in a way that could never have been studied previously. In a series of four articles, we summarize the talks presented at the symposium entitled ‘Bionic women and men – Physiology lessons from implantable cardiac devices’ presented at the 2019 Annual Meeting of The Physiological Society in Aberdeen, UK. The articles highlight the novel questions generated by physiological phenomena observed in LVAD patients and propose future areas of interest within the field of cardiovascular physiology

“Bionic Women and Men” Part 4: Cardiovascular, Cerebrovascular and Exercise Responses Among Patients Supported with Left Ventricular Assist Devices

Current generation left ventricular assist devices (LVADs) have led to significant improvements in survival compared to medical therapy alone, when used for management of patients with advanced heart failure. However, there are a number of side-effects associated with LVAD use, including hypertension, gastrointestinal bleeding, stroke, as well as persistent and severe limitations in functional capacity despite normalization of a resting cardiac output (Qc). These issues are, in large part, related to chronic exposure to a non-physiologic pulse, which contributes to a hyperadrenergic environment characterized by markedly elevated levels of sympathetic nerve activity through a baroreceptor-mediated pathway. In addition, these machines are unable to participate in, or contribute to, normal cardiovascular/autonomic reflexes that attempt to modulate flow through the body. Efforts to advance device technology and develop biologically sensitive devices may resolve these issues, and lead to further improvements in quality-of-life, functional capacity, and ultimately, survival, for the patients they support

“Bionic Women and Men” Part 2: Arterial Stiffness in Heart Failure Patients Implanted with Left Ventricular Assist Devices (LVADs)

In parallel with the major advances in clinical care, technological advancements and implantation of mechanical circulatory support in patients with severe heart failure have resulted in these patients living longer. However, these patients are still at increased risk of stroke and gastrointestinal bleeding. The unique continuous flow produced by various left ventricular assist devices (LVAD) has been suggested as one potential reason for this increased risk of stroke and GI bleeding. Furthermore, these continuous‐flow (CF) devices challenge our understanding of circulatory blood pressure and flow regulation in relation to organ health. In healthy pulsatile and dynamic systems, arterial stiffness is a major independent risk factor for stroke. However, to date, there are limited data regarding the impact of CF‐LVAD therapy on arterial stiffness. The purpose of this report is to discuss the varied impact of CF‐LVAD therapy on arterial stiffness and attempt to highlight some potential mechanisms linking these associations in this unique population

“Bionic Women and Men” Part 3: Right ventricular dysfunction in patients implanted with left ventricular assist devices

The adaptation of the right ventricular (RV) output to a left ventricular assist device (LVAD) often determines the fate of patients with pulmonary hypertension secondary to left heart failure. Pre‐existing right heart dysfunction in patients with advanced left heart failure is the consequence of increased (arterial) afterload and not simply the consequence of myocardial disease. If unaccounted for, it has the potential of accelerating into clinical right heart failure after LVAD, leading to significant morbidity and mortality. After LVAD implantation, the RV has to face increased flow generated by the LVAD, cardiac arrhythmias and exaggerated functional interactions between both ventricles. Understanding the key physiological mechanisms of RV dysfunction in patients with end‐stage heart failure will allow us to predict and therefore prevent RV failure after LVAD implantation

The age-dependent association between aortic pulse wave velocity and telomere length.

KEY POINTS: Age significantly modifies the relationship between aortic pulse wave velocity and telomere length. The differential relationships observed between aortic pulse wave velocity and telomere length in younger and older individuals suggest that the links between cellular and vascular ageing reflect a complex interaction between genetic and environmental factors acting over the life-course. ABSTRACT: Ageing is associated with marked large artery stiffening. Telomere shortening, a marker of cellular ageing, is linked with arterial stiffening. However, the results of existing studies are inconsistent, possibly because of the confounding influence of variable exposure to cardiovascular risk factors. Therefore, we investigated the relationship between telomere length (TL) and aortic stiffness in well-characterized, younger and older healthy adults, who were pre-selected on the basis of having either low or high aortic pulse wave velocity (aPWV), a robust measure of aortic stiffness. Demographic, haemodynamic and biochemical data were drawn from participants in the Anglo-Cardiff Collaborative Trial. Two age groups with an equal sex ratio were examined: those aged 50 years (older). Separately for each age group and sex, DNA samples representing the highest (n = 125) and lowest (n = 125) extremes of aPWV (adjusted for blood pressure) were selected for analysis of leukocyte TL. Ultimately, this yielded complete phenotypic data on 904 individuals. In younger subjects, TL was significantly shorter in those with high aPWV vs. those with low aPWV (P = 0.017). By contrast, in older subjects, TL was significantly longer in those with high aPWV (P = 0.001). Age significantly modified the relationship between aPWV and TL (P < 0.001). Differential relationships are observed between aPWV and TL, with an inverse association in younger individuals and a positive association in older individuals. The links between cellular and vascular ageing reflect a complex interaction between genetic and environmental factors acting over the life-course.Professor Ian B. Wilkinson is a British Heart Foundation Senior Fellow (FS/12/8/29377). Dr Yasmin is supported by the British Heart Foundation (FS/12/8/29377). This work was also supported by the National Institute for Health Research, Cambridge Biomedical Research Centre Award