Control of tissue oxygenation by S-nitrosohemoglobin in human subjects.

S-Nitrosohemoglobin (SNO-Hb) is unique among vasodilators in coupling blood flow to tissue oxygen requirements, thus fulfilling an essential function of the microcirculation. However, this essential physiology has not been tested clinically. Reactive hyperemia following limb ischemia/occlusion is a standard clinical test of microcirculatory function, which has been ascribed to endothelial nitric oxide (NO). However, endothelial NO does not control blood flow governing tissue oxygenation, presenting a major quandary. Here we show in mice and humans that reactive hyperemic responses (i.e., reoxygenation rates following brief ischemia/occlusion) are in fact dependent on SNO-Hb. First, mice deficient in SNO-Hb (i.e., carrying C93A mutant Hb refractory to S-nitrosylation) showed blunted muscle reoxygenation rates and persistent limb ischemia during reactive hyperemia testing. Second, in a diverse group of humans-including healthy subjects and patients with various microcirculatory disorders-strong correlations were found between limb reoxygenation rates following occlusion and both arterial SNO-Hb levels (n = 25; P = 0.042) and SNO-Hb/total HbNO ratios (n = 25; P = 0.009). Secondary analyses showed that patients with peripheral artery disease had significantly reduced SNO-Hb levels and blunted limb reoxygenation rates compared with healthy controls (n = 8 to 11/group; P < 0.05). Low SNO-Hb levels were also observed in sickle cell disease, where occlusive hyperemic testing was deemed contraindicated. Altogether, our findings provide both genetic and clinical support for the role of red blood cells in a standard test of microvascular function. Our results also suggest that SNO-Hb is a biomarker and mediator of blood flow governing tissue oxygenation. Thus, increases in SNO-Hb may improve tissue oxygenation in patients with microcirculatory disorders.

Evaluation of dyspnea of unknown etiology in HIV patients with cardiopulmonary exercise testing and cardiovascular magnetic resonance imaging.

AIM: Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary exercise testing (CPET) coupled with exercise cardiovascular magnetic resonance (CMR) to elucidate etiologies of dyspnea. METHODS AND RESULTS: Thirty-four HIV patients on antiretroviral therapy with dyspnea and exercise limitation (49.7 years, 65% male, mean absolute CD4 count 700) underwent comprehensive evaluation with combined rest and maximal exercise treadmill CMR and CPET. The overall mean oxygen consumption (VO2) peak was reduced at 23.2 ± 6.9 ml/kg/min with 20 patients (58.8% of overall cohort) achieving a respiratory exchange ratio > 1. The ventilatory efficiency (VE)/VCO2 slope was elevated at 36 ± 7.92, while ventilatory reserve (VE: maximal voluntary ventilation (MVV)) was within normal limits. The mean absolute right ventricular (RV) and left ventricular (LV) contractile reserves were preserved at 9.0% ± 11.2 and 9.4% ± 9.4, respectively. The average resting and post-exercise mean average pulmonary artery velocities were 12.2 ± 3.9 cm/s and 18.9 ± 8.3 respectively, which suggested lack of exercise induced pulmonary artery hypertension (PAH). LV but not RV delayed enhancement were identified in five patients. Correlation analysis found no relationship between peak VO2 measures of contractile RV or LV reserve, but LV and RV stroke volume correlated with PET CO2 (p = 0.02, p = 0.03). CONCLUSION: Well treated patients with HIV appear to have conserved RV and LV function, contractile reserve and no evidence of exercise induced PAH. However, we found evidence of impaired ventilation suggesting a non-cardiopulmonary etiology for dyspnea.

The Influence of Exercise on Cardiovascular Health in Sedentary Adults With Human Immunodeficiency Virus.

BACKGROUND: Lifestyle physical activity (ie, moderate physical activity during routine daily activities most days of the week) may benefit human immunodeficiency virus (HIV)-positive adults who are at high risk for cardiovascular disease. OBJECTIVE: The aims of this study were to describe lifestyle physical activity patterns in HIV-positive adults and to examine the influence of lifestyle physical activity on markers of cardiovascular health. Our secondary objective was to compare these relationships between HIV-positive adults and well-matched HIV-uninfected adults. METHODS: A total of 109 HIV-positive adults and 20 control participants wore an ActiGraph accelerometer, completed a maximal graded cardiopulmonary exercise test, completed a coronary computed tomography, completed anthropomorphic measures, and had lipids and measures of insulin resistance measured from peripheral blood. RESULTS: Participants (N = 129) had a mean age of 52 ± 7.3 years, 64% were male (n = 82), and 88% were African American (n = 112). On average, HIV-positive participants engaged in 33 minutes of moderate-to-vigorous physical activity per day (interquartile range, 17-55 minutes) compared with 48 minutes in controls (interquartile range, 30-62 minutes, P = .05). Human immunodeficiency virus-positive adults had poor fitness (peak oxygen uptake [VO2], 16.8 ± 5.2 mL/min per kg; and a ventilatory efficiency, 33.1 [4.6]). A marker of HIV disease (current CD4+ T cell) was associated with reduced peak VO2 (r = -0.20, P < .05) and increased insulin resistance (r = 0.25, P < .01) but not with physical activity or other markers of cardiovascular health (P ≥ 0.05). After controlling for age, gender, body mass index, and HIV status, physical activity was not significantly associated with peak VO2 or ventilatory efficiency. CONCLUSION: Human immunodeficiency virus-positive adults have poor physical activity patterns and diminished cardiovascular health. Future longitudinal studies should examine whether HIV infection blunts the beneficial effects of physical activity on cardiovascular health.

Evaluation of left ventricular ejection fraction using through-time radial GRAPPA.

BACKGROUND: The determination of left ventricular ejection fraction using cardiovascular magnetic resonance (CMR) requires a steady cardiac rhythm for electrocardiogram (ECG) gating and multiple breathholds to minimize respiratory motion artifacts, which often leads to scan times of several minutes. The need for gating and breathholding can be eliminated by employing real-time CMR methods such as through-time radial GRAPPA. The aim of this study is to compare left ventricular cardiac functional parameters obtained using current gold-standard breathhold ECG-gated functional scans with non-gated free-breathing real-time imaging using radial GRAPPA, and to determine whether scan time or the occurrence of artifacts are reduced when using this real-time approach. METHODS: 63 patients were scanned on a 1.5T CMR scanner using both the standard cardiac functional examination with gating and breathholding and the real-time method. Total scan durations were noted. Through-time radial GRAPPA was employed to reconstruct images from the highly accelerated real-time data. The blood volume in the left ventricle was assessed to determine the end systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) for both methods, and images were rated for the presence of artifacts and quality of specific image features by two cardiac readers. Linear regression analysis, Bland-Altman plots and two-sided t-tests were performed to compare the quantitative parameters. A two-sample t-test was performed to compare the scan durations, and a two-sample test of proportion was used to analyze the presence of artifacts. For the reviewers´ ratings the Wilcoxon test for the equality of the scores' distributions was employed. RESULTS: The differences in EF, EDV, and ESV between the gold-standard and real-time methods were not statistically significant (p-values of 0.77, 0.82, and 0.97, respectively). Additionally, the scan time was significantly shorter for the real-time data collection (p<0.001) and fewer artifacts were reported in the real-time images (p<0.01). In the qualitative image analysis, reviewers marginally preferred the standard images although some features including cardiac motion were equivalently rated. CONCLUSION: Real-time functional CMR with through-time radial GRAPPA performed without ECG-gating under free-breathing can be considered as an alternative to gold-standard breathhold cine imaging for the evaluation of ejection fraction in patients.

Direct procurement of wound management products.

This article describes a collaborative project between Bedfordshire Community Health Services and Primary Care Trusts/Clinical Commissioning Groups to improve provision of dressings to nurses for the patients they treat. Commissioners have facilitated a transformational approach and encouraged development of efficient systems of increased cost-effectiveness rather than a transactional approach based on opportunistic cost improvement plans. Reconfiguration to direct procurement from GP prescribing has reduced wastage, released nurse time from processes to spend on clinical contact time with patients, increased efficiency, and reduced prescription workload for GPs, all without adverse effects on expenditure. Establishing a wound care products formulary placed control under the nurses treating patients and facilitated decision-making based on cost-effectiveness in clinical use. Nurses now manage 60% of expenditure in the local community health economy, and this is increasing. Relationships with the dressings manufacturing industry have also changed in a positive, constructive direction.

Platelet and Monocyte Activation After Transcatheter Aortic Valve Replacement (POTENT-TAVR): A Mechanistic Randomized Trial of Ticagrelor Versus Clopidogrel.

Background: Inflammation and thrombosis are often linked mechanistically and are associated with adverse events after transcatheter aortic valve replacement (TAVR). High residual platelet reactivity (HRPR) is especially common when clopidogrel is used in this setting, but its relevance to immune activation is unknown. We sought to determine whether residual activity at the purinergic receptor P2Y12 (P2Y12) promotes prothrombotic immune activation in the setting of TAVR. Methods: This was a randomized trial of 60 patients (enrolled July 2015 through December 2018) assigned to clopidogrel (300mg load, 75mg daily) or ticagrelor (180mg load, 90 mg twice daily) before and for 30 days following TAVR. Co-primary endpoints were P2Y12-dependent platelet activity (Platelet Reactivity Units; VerifyNow) and the proportion of inflammatory (cluster of differentiation [CD] 14+/CD16+) monocytes 1 day after TAVR. Results: Compared to clopidogrel, those randomized to ticagrelor had greater platelet inhibition (median Platelet Reactivity Unit [interquartile range]: (234 [170.0-282.3] vs. 128.5 [86.5-156.5], p < 0.001), but similar inflammatory monocyte proportions (22.2% [18.0%-30.2%] vs. 25.1% [22.1%-31.0%], p = 0.201) 1 day after TAVR. Circulating monocyte-platelet aggregates, soluble CD14 levels, interleukin 6 and 8 levels, and D-dimers were also similar across treatment groups. HRPR was observed in 63% of the clopidogrel arm and was associated with higher inflammatory monocyte proportions. Major bleeding events, pacemaker placement, and mortality did not differ by treatment assignment. Conclusions: Residual P2Y12 activity after TAVR is common in those treated with clopidogrel but ticagrelor does not significantly alter biomarkers of prothrombotic immune activation. HRPR appears to be an indicator (not a cause) of innate immune activation in this setting.

Endothelin-1 and peak oxygen consumption in patients with heart failure with preserved ejection fraction.

BACKGROUND: Mechanisms of exercise intolerance in patients with heart failure with preserved ejection fraction (HFpEF) are not well understood. Pulmonary hypertension, a common accompaniment in patients with HFpEF, is associated with poor outcomes. While Endothelin -1 (ET-1) plays a mechanistic role in pulmonary hypertension, its role in exercise intolerance in HFpEF is not well established. OBJECTIVE: To explore the association between plasma ET-1 levels and maximal oxygen consumption (pVO2), and their changes over 24 weeks in HFpEF. METHODS: This is a post-hoc analysis of the Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Heart Failure with Preserved Ejection Fraction (RELAX) trial. We performed linear regressions to assess the relationship between plasma ET-1 and pVO2. We also used linear regressions to determine whether ET-1 was associated with change in peak VO2 (ΔpVO2). RESULTS: A total of 210 patients were included. Baseline plasma ET-1 levels were associated with older age, higher NT-proBNP levels, higher serum creatinine levels, and higher prevalence of atrial fibrillation. Patients with higher ET1 levels also had higher plasma galectin-3 and CITP levels. After multiple adjustments, baseline ET1 levels were associated with lower pVO2 (ß -0.927, SE 0.196, p < 0.001). Over 24 weeks, the change in ET1 levels was associated with the change in pVO2 (multivariable adjusted ß -0.415, SE 0.115, p = 0.018). Baseline ET1 levels did not modify the effect of sildenafil on change in peak VO2. CONCLUSIONS: Plasma ET1 levels are significantly associated with lower exercise oxygen consumption both at baseline and longitudinally over 24 weeks. Future studies should explore Endothelin-1 antagonism to improve exercise tolerance in HFpEF.

Relationship of HIV Status and Fatigue, Cardiorespiratory Fitness, Myokines, and Physical Activity.

People living with HIV (PLWH) experience high rates of fatigue, which can be improved with physical activity. We examined relationships between HIV infection, fatigue, cardiorespiratory fitness, physical activity, and myokines. Twenty PLWH and 20 HIV-uninfected adults completed a fatigue assessment, a maximal cardiometabolic exercise test, serum measures of myokines, and wore an accelerometer for 7 days. Measures were completed at baseline, 3 months, and 6 months. At baseline, PLWH had more fatigue (4.7 ± 2.6 vs. 2.8 ± 2.5, p = .01) and higher peak ventilatory efficiency (VE/VCO2; 33 ± 5.5 vs. 30.2 ± 2.5; p = .06). Half of PLWH engaged in at least one 10-minute bout of physical activity in the previous week, compared with control subjects (65%). Over time, HIV infection and fibroblast growth factor 21 were associated with fatigue (p < .05). People living with HIV have more fatigue and a higher ventilatory efficiency; expression of fibroblast growth factor 21 may underpin this relationship.

Cardiorespiratory fitness is associated with inflammation and physical activity in HIV+ adults.

OBJECTIVE: Our objective was to examine the effect of a lifestyle diet and exercise intervention on cardiorespiratory fitness (CRF) and to examine predictors of change in CRF. DESIGN: People living with HIV (PLHIV) are at increased risk for cardiovascular disease. CRF is a better predictor of cardiovascular disease-related mortality than established risk factors yet very little is known about CRF in PLHIV. METHODS: One-hundred and seven virally suppressed PLHIV were randomized to a group-based intervention to improve lifestyle behaviors or a control condition. All PLHIV maximal cardiorespiratory stress test to determine VO2 peak, VO2 at anaerobic threshold, and ventilatory efficiency/VCO2, at baseline and 6 months later. Participants wore an accelerometer to measure physical activity, completed waist-hip circumference measures, and had a fasting lipid profile, IL-6, and high sensitivity C-reactive protein analyzed. Generalized estimating equations were used to examine the effect of the intervention on CRF and predictors of change in CRF. RESULTS: Participants were approximately 53 years old, 65% male (n = 70), and 86% African-American (n = 93). There was no effect of the intervention on markers of CRF over time (P > 0.05). After controlling for age, sex, waist-hip-ratio, the inflammatory biomarker IL-6 was inversely associated with a decline in both VO2 peak (P = 0.03) and VO2 at anaerobic threshold (P = 0.03). In addition, participants who walked an additional 10 000 steps per day had a 2.69 ml/kg per min higher VO2 peak (P = 0.02). CONCLUSION: Despite HIV viral suppression, PLHIV had remarkably poor CRF and inflammation was associated with a clinically adverse CRF profile. However, increased physical activity was associated with improved CRF.

Pharmacologic Targeting of Red Blood Cells to Improve Tissue Oxygenation.

Disruption of microvascular blood flow is a common cause of tissue hypoxia in disease, yet no therapies are available that directly target the microvasculature to improve tissue oxygenation. Red blood cells (RBCs) autoregulate blood flow through S-nitroso-hemoglobin (SNO-Hb)-mediated export of nitric oxide (NO) bioactivity. We therefore tested the idea that pharmacological enhancement of RBCs using the S-nitrosylating agent ethyl nitrite (ENO) may provide a novel approach to improve tissue oxygenation. Serial ENO dosing was carried out in sheep (1-400 ppm) and humans (1-100 ppm) at normoxia and at reduced fraction of inspired oxygen (FiO2 ). ENO increased RBC SNO-Hb levels, corrected hypoxia-induced deficits in tissue oxygenation, and improved measures of oxygen utilization in both species. No adverse effects or safety concerns were identified. Inasmuch as impaired oxygenation is a major cause of morbidity and mortality, ENO may have widespread therapeutic utility, providing a first-in-class agent targeting the microvasculature.

Design of the exercise MRI evaluation of HIV-pulmonary arterial hypertension longitudinal determinants (EXALTED) trial.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a potentially serious cause of dyspnea and exercise limitation in patients with HIV infection. In this trial, we propose using exercise MRI in conjunction with cardiopulmonary testing to delineate PAH from other causes of cardiovascular dysfunction, identify individuals with exercise-induced PAH who are at high risk of developing resting PAH, and provide longitudinal estimates of progression of PAH and right ventricular function. METHODS: In this prospective observational study, HIV patients with dyspnea and exercise limitation in the absence of identifiable causes and those who meet the inclusion criteria will be enrolled based on resting pulmonary artery pressure (≤ or >40 mmHg) on a screening echocardiogram and exercise limitation on the Modified Medical Research Council dyspnea scale. Patients without evidence of resting PAH will be enrolled into both rest and exercise MRI and cardiopulmonary testing protocol, whereas patients with evidence of PAH on resting echocardiograms will undergo only resting cardiac MRI studies to evaluate right ventricular function and fibrosis. Both patient subgroups will be followed for 24 months to obtain longitudinal progression of the disease. In a sub-study, we will further analyze inflammatory variables that may predict these changes, thus allowing early identification of these patients. IMPLICATIONS AND CONCLUSIONS: This trial will be the first study to provide an understanding of the mechanisms underpinning the functional deterioration of the right ventricle in patients with HIV and will impart insight into the immune mediators of PAH progression and right ventricular functional deterioration in patients with HIV-PAH.

Multimodal imaging of the tricuspid valve: normal appearance and pathological entities.

The tricuspid valve, which is the atrioventricular valve attached to the morphological right ventricle, is affected by a wide range of pathological processes. Tricuspid valve diseases are now increasingly recognized as a significant cause of morbidity and mortality. Echocardiography is the most widely available and, hence, the first-line imaging modality used in the evaluation of tricuspid valve disorders; however, CT and MRI are also increasingly used for further evaluation and characterization of these entities. In this article, we first review the normal anatomy and embryology of the tricuspid valve, followed by a discussion of the role of multiple imaging modalities in the evaluation of tricuspid valve abnormalities. We then review and illustrate the imaging appearance of several congenital and acquired tricuspid valve abnormalities. Main Messages • Tricuspid valve diseases have a significant impact on morbidity and mortality. • CT and MRI are increasingly used in the evaluation of tricuspid disorders. • CT and MRI help in diagnosis, functional evaluation, pre-surgical planning and post-surgical follow-up. • The most common cause of tricuspid regurgitation is functional.