Changes In VO2 Research Articles

Switchable terahertz polarization converter based on VO2 metamaterial

A switchable terahertz (THz) polarization converter based on vanadium dioxide (VO2) metamaterial is proposed. It is a 5-layer structure which containing metal split-ring-resonator (SRR), the first polyimide (PI) spacer, VO2 film, the second PI spacer, and metal grating. It is an array structure and the period in x and y directions is 100 μm. The performance is simulated by using finite integration technology. The simulation results show that, when the VO2 is in insulating state, the device is a transmission polarization converter. The cross-linear polarization conversion can be realized in a broadband of 0.70 THz, and the polarization conversion rate (PCR) is higher than 99%. Under thermal stimulus, the VO2 changes from insulating state to metallic state, and the device is a reflective polarization converter. The linear-to-circular polarization conversion can be successfully realized in a broadband of 0.50 THz, and the PCR is higher than 88%.

Meta-analysis addressing the impact of cardiovascular-acting medication on peak oxygen uptake of patients with HFpEF.

As our therapeutic armamentarium for HFpEF is insufficient, research has been focusing on the potential beneficial effect of existing pharmaceutical regimens on this specific patient population. A series of RCTs have recently examined the impact of various pharmaceutical treatments with proven benefit in HFrEF, on the improvement of symptoms of HFpEF patients. This systematic review and meta-analysis comprised studies of adult patients with HFpEF and evaluated the impact of different cardiovascular acting medication on cardiorespiratory fitness, reflected by peak VO2 values measured during CPET. The primary outcome was difference between groups in the change of peak VO2 (ΔpeakVO2). Literature search involved PubMed/MEDLINE, Scopus and Web of Science databases. Our search identified 3634 records and 19 studies were included in qualitative analysis; 12 studies with 1341 patients were finally included in primary outcome analysis. ΔpeakVO2 between baseline and study-end did not significantly change after treatment with spironolactone, ivabradine, sildenafil, or oral inorganic nitrate and neither did difference in 6MWT distance after treatment with spironolactone. Spironolactone led to statistically significant reduction in E/E' ratio study-end values (WMD - 1.64, 95%CI - 2.42 to - 0.86, I2 = 87%, p < 0.0001), as well as to a significant increase in MLHFQ values (WMD 0.75, 95%CI 0.02 to 1.48, I2 = 0%, p = 0.65), indicating deterioration in HRQoL among HFpEF patients. A series of established cardiovascular acting medication in HFrEF seems not to confer significant benefit in peak VO2 and 6MWT distance in HFpEF. Spironolactone is associated with improvements in diastolic function and with a significant deterioration in HRQoL of this population.

Sex-related Differences in Exercise Capacity Trends and Determinants after Cardiac Rehabilitation in Patients with Acute Myocardial Infarction.

This study aimed to investigate whether longitudinal changes in exercise capacity in patients with acute myocardial infarction (AMI) differ by sex and clarified what contributed to these differences. We retrospectively examined the differences in each variable between men and women in 156 patients with AMI (mean age: 65 ± 12 years; 82.0% male) who participated in a 3-month cardiac rehabilitation (CR) program and could be followed-up for exercise capacity 12-months after AMI onset. Sex-related differences in the change in peak oxygen uptake (peak VO2) at baseline, 3-months, and 12-months after AMI were analyzed. Male patients with AMI were younger and had higher body mass index and employment rate than women. The attendance of the CR program was higher in women (men vs. women; 10 [3-15] vs. 14 [11-24] sessions, p = 0.0002). Women showed a significant lower %change in peak VO2 after 12 months (men vs. women; 7.8% [-0.49% to 14.6%] vs. 1.3% [-5.7% to 7.5%], p = 0.013). In multiple linear regression analysis, age (β = -0.76, 95% confidence interval [CI] = -1.0 to -0.50, p <0.0001) and female sex (β = -6.3, 95% CI = -9.1 to -3.5, p <0.0001) were negative independent predictors of change in peak VO2 over 12 months, while CR attendance (β = 0.21, 95% CI = 0.0032-0.42, p = 0.047) and recommended exercise habit after the CR program (β = 2.1, 95% CI = 0.095-4.1, p = 0.040) were positive independent predictors of change in peak VO2 over 12 months. In female patients, exercise capacity improved during the CR program but decreased to AMI onset levels after 12 months.

Exoskeleton Training and Trans-Spinal Stimulation for Physical Activity Enhancement After Spinal Cord Injury (EXTra-SCI): An Exploratory Study.

After spinal cord injury (SCI) physical activity levels decrease drastically, leading to numerous secondary health complications. Exoskeleton-assisted walking (EAW) may be one way to improve physical activity for adults with SCI and potentially alleviate secondary health complications. The effects of EAW may be limited, however, since exoskeletons induce passive movement for users who cannot volitionally contribute to walking. Trans-spinal stimulation (TSS) has shown the potential to enable those with even the most severe SCI to actively contribute to movements during EAW. To explore the effects of EAW training on improving secondary health complications in persons with SCI, participants with chronic (n = 8) were enrolled in an EAW program 2–3 times per week for 12 weeks. Anthropometrics (seated and supine waist and abdominal circumferences (WC and AC), body composition assessment (dual exposure x-ray absorptiometry-derived body fat percent, lean mass and total mass for the total body, legs, and trunk), and peak oxygen consumption (VO2 during a 6-minute walk test [6MWT]) were assessed before and after 12 weeks of EAW training. A subset of participants (n = 3) completed EAW training with concurrent TSS, and neuromuscular activity of locomotor muscles was assessed during a 10-m walk test (10MWT) with and without TSS following 12 weeks of EAW training. Upon completion of 12 weeks of training, reductions from baseline (BL) were found in seated WC (−2.2%, P = 0.036), seated AC (−2.9%, P = 0.05), and supine AC (−3.9%, P = 0.017). Percent fat was also reduced from BL for the total body (−1.4%, P = 0.018), leg (−1.3%, P = 0.018), and trunk (−2%, P = 0.036) regions. No effects were found for peak VO2. The addition of TSS for three individuals yielded individualized responses but generally increased knee extensor activity during EAW. Two of three participants who received TSS were also able to initiate more steps without additional assistance from the exoskeleton during a 10MWT. In summary, 12 weeks of EAW training significantly attenuated markers of obesity relevant to cardiometabolic health in eight men with chronic SCI. Changes in VO2 and neuromuscular activity with vs. without TSS were highly individualized and yielded no overall group effects.

Correlation between changes in arterial blood oxygen partial pressure, oxygen uptake and carbon dioxide elimination by the lungs with changes in positive end expiratory pressure: a prospective observational study

INTRODUCTION: Since mechanical ventilation remains the main tool of respiratory support, ventilatory aspect of lung function fixed researchers’ attention during last decades, which is reflected by open lung concept and lung-protective ventilation strategy. However, it seems logical to assess function of the lung — biphasic mass exchanger with limited capacity — measuring its gas exchange performance, depending upon lung perfusion the same extent as ventilation. Recently clinicians have got routine access to metabolographers, providing figures of lungs oxygen absorption (VO2) and carbon dioxide exhalation (VCO2). OBJECTIVE: To evaluate interchangeability of metabolographer data and arterial blood gases analysis as tools for positive end-expiratory pressure (PEEP) titration by comparison of dynamic VO2 and VCO2 changes with PaO2 shifts after standardized PEEP changing. MATERIALS AND METHODS: A single-center prospective observational study included 41 patients underwent mechanical ventilation during general anesthesia for elective non-cardiothoracic surgery. After anesthesia induction and monitored parameters stabilization, PaO2, VCO2 and VO2 were measured before and after PEEP increasing from 2 to 5 mbar. Correlation was evaluated using Spearman coefficient in R-Studio with ggplot2 visualization package. RESULTS: After PEEP level increase, in 14 patients PaO2 changes were &lt; 5 %, in 15 patients PaO2 increase was observed, and in 12 patients PaO2 has decreased. The Spearman correlation coefficient (rh) between VCO2 and PaO2 was 0.77 (р-value = 3.75 × 10−9), between VO2 and PaO2 — rh = 0.92 (p-value = 2.2 × 10−16). CONCLUSIONS: The VCO2 and VO2 dynamic changes obtained using metabolographer demonstrates high correlation with PaO2 shifts followed PEEP changes, which makes the dynamic analysis of the first two indicators a possible non-invasive alternative for repeated arterial blood gases analysis during РЕЕР level titration. Notable fact is that in significant proportion of observations, PEEP level of 5 mbar, often recommended “by default” for lung-protective ventilation, is excessive from gas exchange performance point of view.

Photoinduced Multistable Resonance Frequency Switching of Phase Change Microstring at Room Temperature

AbstractVanadium dioxide (VO2), a promising phase change material, exhibits insulator to metal transition at 68 °C, manifests a drastic change in multiple physical properties, such as electrical resistance, mechanical modulus, lattice parameters, etc. From technological perspective, the transition temperature can be reduced by precise strain engineering. Here a noncontact, all‐optical, and highly energy efficient platform is demonstrated to study macroscopic dynamics related to the localized structural rearrangements at room temperature. A thin layer (≈25 nm) of polycrystalline VO2 deposited on a platinum coated silicon nitride microstring resonator shows a fast controlled mechanical resonance frequency response upon variations in optical power and wavelength. It is shown multiple stable frequencies of the resonator, designated as different equilibrium states, can be activated at different optical powers (≈200 µW) and wavelength, i.e., 450, 520, and 635 nm. The observed multiple resonance states of the microstring are explained because of the generation of stress due to the interplay between thermal expansion and the temperature‐induced phase change of VO2. It is believed this change in frequency states under the controlled external optical excitation can have potential applications in ultrafast optical switching, intelligent temperature sensors, and neuromorphic devices operated at room temperature.

Short-term results of serial cardiopulmonary exercise testing in adults with repaired coarctation of the aorta

Background Data on the evolution of exercise capacity in adults with repaired coarctation of the aorta (CoA) are scarce. We aimed to investigate the evolution and change of measures of exercise capacity obtained by cardiopulmonary exercise testing (CPET) in adults with repaired CoA. Methods Patients 16 years of age and older with CoA, who performed at least two maximal CPETs in our institution, were included in the study. The first and last available tests were used for comparative statistical analysis of common exercise variables. Results Sixty patients (43 men) performed serial maximal CPET. Mean age at first assessment was 30 ± 10 years (range 17–68). Mean time between first and last assessment was 3.5 years (range 1–7). Mean peak VO2 was 85.6 ± 20.4% of the predicted value at the initial test, and 87.0 ± 20.5% at the final test (p = 0.294). There were no significant differences in the mean values of oxygen pulse, VO2 at anaerobic threshold, systolic and diastolic blood pressures and peak heart rate between the two assessments. There was a slightly higher VE/VCO2 slope at the final test (p = 0.047). Higher age and Borg scale were found to be related with a decline in percent-predicted peak VO2 from initial to final assessment. Conclusion In adults with repaired CoA, we found no significant change in peak VO2 during a mean follow-up of 3.5 years, yet a small increase in VE/VCO2 slope was observed. Higher age was predictive for a decline in percent-predicted peak VO2, starting in the third decade of life.

Changes in carbon dioxide production and oxygen uptake evaluated using indirect calorimetry in mechanically ventilated patients with sepsis

BackgroundSeveral clinical guidelines recommend monitoring blood lactate levels and central venous oxygen saturation for hemodynamic management of patients with sepsis. We hypothesized that carbon dioxide production (VCO2) and oxygen extraction (VO2) evaluated using indirect calorimetry (IC) might provide additional information to understand the dynamic metabolic changes in sepsis.MethodsAdult patients with sepsis who required mechanical ventilation in the intensive care unit (ICU) of our hospital between September 2019 and March 2020 were prospectively enrolled. Sepsis was diagnosed according to Sepsis-3. Continuous measurement of VCO2 and VO2 using IC for 2 h was conducted within 24 h after tracheal intubation, and the changes in VCO2 and VO2 over 2 h were calculated as the slopes by linear regression analysis. Furthermore, temporal lactate changes were evaluated. The primary outcome was 28-day survival.ResultsThirty-four patients with sepsis were enrolled, 26 of whom survived 76%. Significant differences in the slope of VCO2 (− 1.412 vs. − 0.446) (p = 0.012) and VO2 (− 2.098 vs. − 0.851) (p = 0.023) changes were observed between non-survivors and survivors. Of note, all eight non-survivors and 17 of the 26 survivors showed negative slopes of VCO2 and VO2 changes. For these patients, 17 survivors had a median lactate of − 2.4% changes per hour (%/h), whereas non-survivors had a median lactate of 2.6%/hr (p = 0.023).ConclusionsThe non-survivors in this study showed temporal decreases in both VCO2 and VO2 along with lactate elevation. Monitoring the temporal changes in VCO2 and VO2 along with blood lactate levels may be useful in predicting the prognosis of sepsis.

Effect of self-tailored high-intensity interval training versus moderate-intensity continuous exercise on cardiorespiratory fitness after myocardial infarction: A randomised controlled trial

BackgroundWhether high-intensity interval training (HIIT) is more efficient than moderate-intensity continuous exercise (MICE) to increase cardiorespiratory fitness in patients with acute coronary syndrome at moderate-to-high cardiovascular risk is controversial. The best approach to guide training intensity remains to be determined. ObjectiveWe aimed to assess intensities achieved with self-tailored HIIT and MICE according to perceived exertion and to compare the effect on cardiorespiratory fitness in patients early after ST-elevation myocardial infarction (STEMI). MethodsWe included 69 males starting cardiac rehabilitation within 4 weeks after STEMI. After a 3-week run-in phase with MICE, 35 patients were randomised to 9 weeks of HIIT (2×HIIT and 1×MICE per week) and 34 patients to MICE (3×MICE). Training workload for MICE was initially set at the patients’ first ventilatory threshold (VT). HIIT consisted of 4×4-min intervals with a workload above the second VT in high intervals. Training intensity was adjusted weekly to maintain the perceived exertion (Borg score 13–14 for MICE, ≥15 for HIIT). Session duration was 38min in both groups. Peak oxygen consumption (VO2) was measured by cardiopulmonary exercise testing pre- and post-intervention. ResultsBoth groups improved peak VO2 (ml/kg/min) (HIIT +1.9, P<0.001; MICE +3.2, P<0.001, Cohen's d −0.4), but changes in VO2 were not significantly different between groups (P=0.104). Exercise regimes did not differ between groups in terms of energy expenditure or training time, but perceived exertion was higher with HIIT. ConclusionsSelf-tailored HIIT was feasible in patients early after STEMI. It was more strenuous but not superior nor more time-efficient than MICE in improving peak VO2.The trial was registered at ClinicalTrial.gov (NCT02627586).

Abstract 11388: Multimorbidity Moderates Changes in Peak Oxygen Uptake in Cardiac Rehabilitation Patients

Introduction: Patients undergoing cardiac rehabilitation (CR) exhibit various degrees of illness severity and high prevalence of chronic conditions (CC). Cardiorespiratory fitness (CRF) is a key predictor of outcomes in patients with cardiovascular disease. Participation in CR is associated with increased CRF, reduced future cardiovascular events, and mortality. Peak oxygen uptake (VO 2 ) is the gold-standard method to evaluate CRF; however, the burden of multimorbidity and its impact on CRF improvement has not been extensively studied. Methods: We included 618 patients who were ≥ 18 years old and underwent cardiopulmonary exercise testing prior to and after CR at Mayo Clinic. Using the Rochester Epidemiology Project records- linkage system, we assessed the prevalence of 18 CC defined by the US Department of Health and Human Services. To evaluate changes in peak VO 2 in patients with multimorbidity (categorized as ≥6 CC), we created logistic regression models adjusting for age, sex, and baseline peak VO 2 . Results: Mean age was 61.5 ± 11.0 years and 75.5% were male. Most patients (81.2%) attended ≥18 CR sessions. Half (50.4%) of patients had at least 6 CC (median 6; range 0-13). Overall, peak VO 2 at baseline was 20.7 ± 6.3 mL/kg per min and the percent change in peak VO 2 following CR was 11.4% ± 21.6%, Figure 1A . Multimorbidity was associated with lower improvement in peak VO 2 following CR compared to patients with &lt;6 CC (7.5% vs 11.4%, p=0.0001). Furthermore, across categories of CRF improvement (i.e., 1%, 5%, and 10% percent change in peak VO 2 ) lower multimorbidity was associated with a 1.5-2-fold increase in CRF when compared to those with higher multimorbidity (≥6 CC), Figure 1B . Conclusions: Patients entering CR have a high multimorbidity burden. Our results suggest that multimorbidity in CR patients attenuates improvement in peak VO 2 . Individualized interventions should focus on managing and reducing multimorbidity to minimize the negative impact on CRF improvement.

The Effect of Voxelotor on Exercise Capacity of Youths with Sickle Cell Anemia

Background/Hypothesis: Children and adults with sickle cell anemia (SCA) exhibit decreased cardiopulmonary fitness. Anemia is directly related to oxygen carrying capacity and is one factor that affects cardiopulmonary fitness. The new sickle cell drug voxelotor raises hemoglobin in patients with SCA treated or untreated with hydroxyurea. We hypothesized that voxelotor improves exercise capacity in youths with SCA.Methods: A single-center, open-label, single-arm longitudinal interventional pilot study was conducted for patients with SCA age > 12. Participants performed baseline Cardiopulmonary Exercise Testing (CPET#1), took 1500mg voxelotor for 2 months, then CPET was repeated (CPET#2). A modified Bruce Protocol using 2-minute stages was performed on a motorized treadmill, for a goal of 8-12 minutes of exercise. Breath by breath gas exchange data were collected and analyzed using a VMax Encore 29C metabolic cart. The metabolic test included standard monitoring of heart rate, EKG ST changes, arrhythmias, and O2 saturation. A respiratory quotient >1.1 was used as evidence of participant effort. Peak oxygen consumption (peak VO2), anaerobic threshold (AT), O2 pulse, VE/VCO2 slope, and time exercised in CPET#1 and CPET#2 were compared for each participant. The primary endpoint was peak VO2.Hemoglobin (Hgb), reticulocyte count, and bilirubin were measured before CPET#1 and CPET#2. Pill count was used to monitor medication adherence and left shift of the P50 oxygen dissociation curve was used to document biochemical effect of voxelotor. Patient Global Impression of Change (PGIC) and Clinician Global Impression of Change (CGIC) surveys were collected at the end of the study.Statistical analysis was performed using Student's paired T-test.Results: Nine SCA patients ages 12-20, including 4 males and 5 females, completed the study. All had Hgb SS and were stably maintained on hydroxyurea, which was continued without dose change during the study. After 2 months of voxelotor, all participants demonstrated expected hematologic changes, including mean rise in Hgb +1.3 g/dL (95% C.I.= 0.8, 1.7), mean decrease in reticulocyte count -2.4% (95% C.I.= -4.1, -0.8), and mean decrease in bilirubin -0.4 mg/dL (95% C.I.= -0.8, -0.1). All participants demonstrated voxelotor adherence and leftward shift of p50 (Table 1).Oxygen consumption, measured as percent predicted peak VO2 (ml/kg/min), ranged from 52% to 80% in CPET#1 and from 55% to 71% in CPET#2. The changes in peak VO2 for individual participants ranged from -10% to +10% of predicted peak VO2, with a mean difference of -2.2% (95% CI = -7.1, 2.7), which is insignificant (p=0.3). Using +/- 6% as variability in peak VO2 measurement, 5 participants exhibited no change, 3 participants had decrease in peak VO2 of -7%, -9%, and -10%, while peak VO2 increased by +10% for a single participant, who started to exercise on his own after starting voxelotor. Changes in individuals' anaerobic threshold, O2 pulse, VE/VCO2 slope, and time exercised were not significant and did not correlate with changes in peak VO2. All participants achieved respiratory quotient >1.1, assuring participant effort during CPET (Table 2).On the 7-point PGIC questionnaire evaluating activity limitations, symptoms, emotions, and overall quality of life, 7 out of 9 participants reported positive change, including “a great deal better,” “definite,” and “moderate” improvements. Two participants reported minimal to no change, and no participants reported worsening. In comparison, clinicians reported “minimal” to “much” improvement on CGIC for all participants. Overall, patient impression of improvement was higher than clinician impression of improvement.Conclusion: This pilot study demonstrated the feasibility of using CPET to evaluate exercise capacity longitudinally in youths with SCA. After addition of voxelotor to hydroxyurea for 2 months, all patients perceived global improvement. Peak VO2 did not change in 8 out of 9 participants and improved for 1 participant who exercised between the 2 CPETs. To increase peak VO2, higher Hgb increase, concurrent regular exercise, and longer exposure to voxelotor may be necessary.This study was funded by Global Blood Therapeutics [Display omitted] DisclosuresLarkin: Forma Therapeutics, Inc.: Research Funding. Dulman: Pfizer: Other: own stock. Kuypers: Forma Therapeutics, Inc.: Research Funding.

Effect of β-Blocker Withdrawal on Functional Capacity in Heart Failure and Preserved Ejection Fraction

BackgroundChronotropic incompetence has shown to be associated with a decrease in exercise capacity in heart failure with preserved ejection fraction (HFpEF), yet β-blockers are commonly used in HFpEF despite the lack of robust evidence. ObjectivesThis study aimed to evaluate the effect of β-blocker withdrawal on peak oxygen consumption (peak Vo2) in patients with HFpEF and chronotropic incompetence. MethodsThis is a multicenter, randomized, investigator-blinded, crossover clinical trial consisting of 2 treatment periods of 2 weeks separated by a washout period of 2 weeks. Patients with stable HFpEF, New York Heart Association functional classes II and III, previous treatment with β-blockers, and chronotropic incompetence were first randomized to withdrawing from (arm A: n = 26) versus continuing (arm B: n = 26) β-blocker treatment and were then crossed over to receive the opposite intervention. Changes in peak Vo2 and percentage of predicted peak Vo2 (peak Vo2%) measured at the end of the trial were the primary outcome measures. To account for the paired-data nature of this crossover trial, linear mixed regression analysis was used. ResultsThe mean age was 72.6 ± 13.1 years, and most of the patients were women (59.6%) in New York Heart Association functional class II (66.7%). The mean peakVo2 and peak Vo2% were 12.4 ± 2.9 mL/kg/min, and 72.4 ± 17.8%, respectively. No significant baseline differences were found across treatment arms. Peak Vo2 and peak Vo2% increased significantly after β-blocker withdrawal (14.3 vs 12.2 mL/kg/min [Δ +2.1 mL/kg/min]; P < 0.001 and 81.1 vs 69.4% [Δ +11.7%]; P < 0.001, respectively). Conclusionsβ-blocker withdrawal improved maximal functional capacity in patients with HFpEF and chronotropic incompetence. β-blocker use in HFpEF deserves profound re-evaluation. (β-blockers Withdrawal in Patients With HFpEF and Chronotropic Incompetence: Effect on Functional Capacity [PRESERVE-HR]; NCT03871803; 2017-005077-39)

Training responsiveness of cardiorespiratory fitness and arterial stiffness following moderate-intensity continuous training and high-intensity interval training in adults with intellectual and developmental disabilities.

Cardiorespiratory fitness (CRF) prompts antiatherogenic adaptations in vascular function and structure. However, there is an extraordinary interindividual variability in response to a standard dose of exercise, wherein a substantial number of adults with intellectual and developmental disabilities (IDD) do not improve CRF. We (1) evaluated the effects of 12-month of moderate-intensity continuous training (MICT) on CRF and arterial stiffness and (2) tested whether an additional 3-month of high-intensity interval training (HIIT) would add to improvements in CRF responsiveness and arterial stiffness. Fifteen adults with mild-to-moderate IDD (male adults=9, 30.1±7.5years old) met 3days per week for 30min MICT for 12months, after which the incidence of CRF responsiveness was calculated (≥5.0% change in absolute peak VO2 ). Thereafter, responders and non-responders started HIIT for 3months with identical daily training load/frequency. Peak VO2 , local and regional indices of arterial stiffness were assessed prior to and after each period. Sixty per cent of the participants were non-responders following MICT, but the incidence dropped to 20% following HIIT (P=0.03). Absolute peak VO2 values reached significant difference from pre-intervention (+0.38±0.08Lmin-1 , P=0.001) only when HIIT was added. Lower limb pulse wave velocity (PWV) decreased following MICT (-0.8±1.1ms-1 , P=0.049), whereas central PWV only decreased following HIIT (-0.8±0.9ms-1 , P=0.013). Cardiorespiratory fitness responsiveness and reductions in PWV to a 12-month MICT period in adults with IDD improved following a period of HIIT programme inducing higher metabolic stress.

Effect of exercise training on vascular function and endothelial repair in heart failure with preserved ejection fraction: results from the OptimEx trial

Abstract Background Exercise training improves peak oxygen uptake (VO2) in heart failure with preserved ejection fraction (HFpEF), but the underlying mechanisms are unknown. In other cardiovascular diseases, exercise training improves vascular function and increases levels of circulating endothelium-repairing cells. We aimed to investigate the effects of moderate continuous training (MCT) and high intensity interval training (HIIT) on vascular function and cellular endothelial repair in HFpEF. Methods This was a prespecified subanalysis of the Optimizing Exercise Training in Prevention and Treatment of Diastolic Heart Failure randomized trial. HFpEF patients (n=180) were randomized to HIIT, MCT or attention control. At baseline and after 12 weeks, we measured peak VO2, fingertip arterial tonometry (n=109), brachial artery flow-mediated dilation (n=59), aortic pulse wave velocity (n=94), and flow cytometry (n=136) for endothelial progenitor cells (CD45dimCD34+VEGFR2+) and angiogenic T cells (CD3+CD31+CD184+). Changes in these parameters were compared between groups using linear mixed models. Parameters were correlated using Spearman's rho. Results At 3 months, we did not observe significant differences between HIIT, MCT and control group regarding changes in vascular function throughout the vascular tree (fingertip arterial tonometry, brachial artery flow-mediated dilation and central arterial stiffness, Table 1) or levels of circulating endothelium-repairing cells (endothelial progenitor cells and angiogenic T cells, Table 1). Results were similar at 12 months and when restricting analysis to patients with at least 70% adherence to training sessions. Patients with higher peak VO2 at baseline had lower numbers of circulating endothelial progenitor cells (rho=−0.22, p=0.011). Conclusions In patients with HFpEF, exercise training did not change vascular function or levels of endothelium-repairing cells. Thus, improved vascular function likely does not contribute to the change in peak VO2 after training. These findings are in contrast with the benefits of exercise on vascular function in heart failure with reduced ejection fraction and coronary artery disease. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): EU Framework Programme 7 Table 1

A randomized clinical trial on the short-term effects of 12-week sacubitril/valsartan vs. enalapril on peak oxygen consumption in patients with heart failure with reduced ejection fraction: results from the ACTIVITY-HF study.

ACTIVITY-HF was a randomized, double-blind, active-controlled study, which assessed the short-term effect of sacubitril/valsartan compared with the active comparator enalapril on improving maximal exercise capacity in patients with heart failure with reduced ejection fraction (HFrEF). A total of 201 ambulatory patients with HFrEF (left ventricular ejection fraction ≤ 40%, New York Heart Association class III) across 34 centres in Germany were randomized (1:1) to receive sacubitril/valsartan 97/103 mg bid (n=103) or enalapril 10mg bid (n=98). The primary endpoint of the study was the change from baseline in peak oxygen consumption (VO2 ; adjusted to body weight) after 12 weeks, and the key secondary endpoint was change from baseline in peak VO2 after 6 weeks. The study population was predominantly male (81.1%) with a mean age of 66.9 years and a body mass index of 29.4kg/m2 . Change in peak VO2 from baseline to Week 12 was similar between sacubitril/valsartan and enalapril groups [least squares mean difference: 0.32 mL/min/kg; 95% confidence interval (CI) -0.21, 0.85; P=0.2327]. Similarly, no significant differences were observed between the two treatment groups in minute ventilation to carbon dioxide production slope, exercise capacity at first ventilatory threshold or Borg scale at either Week 6 or Week 12. Change in heart rate at first ventilatory threshold was lower in the sacubitril/valsartan group compared with the enalapril group at Week 12 (mean -3.75 bpm; 95% CI -7.03, -0.48; P=0.0248). The safety of sacubitril/valsartan was comparable to enalapril. In patients with HFrEF, short-term treatment with sacubitril/valsartan for 12 weeks did not result in significant benefits on peak VO2 when compared with enalapril.

Tuning of Optical Phonons in α-MoO3-VO2 Multilayers.

Merging the properties of VO2 and van der Waals (vdW) materials has given rise to novel tunable photonic devices. Despite recent studies on the effect of the phase change of VO2 on tuning near-field optical response of phonon polaritons in the infrared range, active tuning of optical phonons (OPhs) using far-field techniques has been scarce. Here, we investigate the tunability of OPhs of α-MoO3 in a multilayer structure with VO2. Our experiments show the frequency and intensity tuning of 2 cm-1 and 11% for OPhs in the [100] direction and 2 cm-1 and 28% for OPhs in the [010] crystal direction of α-MoO3. Using the effective medium theory and dielectric models of each layer, we verify these findings with simulations. We then use loss tangent analysis and remove the effect of the substrate to understand the origin of these spectral characteristics. We expect that these findings will assist in intelligently designing tunable photonic devices for infrared applications, such as tunable camouflage and radiative cooling devices.

Depressive symptoms interfere with the improvement in exercise capacity by cardiac rehabilitation after left ventricular assist device implantation.

Although depressive symptoms are associated with an increased risk of readmission after left ventricular assist device (LVAD) implantation, it is unclear whether they affect the efficacy of exercise-based cardiac rehabilitation (EBCR). This study aimed to investigate the effect of depressive symptoms on EBCR efficacy. We analyzed 48 patients who participated in EBCR after LVAD implantation (mean age 45±12years; 60% male). Patients were classified into two groups using the Zung Self-Rating Depression Scale (SDS): depressive group (SDS ≥40, n=27) and non-depressive group (SDS <40, n=21). We examined changes in peak oxygen uptake (VO2 ), knee extensor muscular strength (KEMS), and quality of life (QOL) during EBCR using analysis of covariance. Although baseline characteristics were similar between the two groups, the non-depressive group was less likely to receive diuretics (22% vs. 52%, p=0.030). Peak VO2 , KEMS, and QOL significantly increased over time in both groups (all p<0.05). The depressive group had a significantly lower change in peak VO2 than the non-depressive group (2.7 vs. 1.6ml/kg/min; mean difference: -1.1ml/kg/min, 95% confidence interval [CI]: -0.045 to -2.17; p=0.041, d=0.59). There was no between-group difference regarding the change in KEMS or QOL. Adjusting for the baseline value, a significant difference between groups was observed only in peak VO2 (p=0.045). Although EBCR significantly improved exercise capacity after LVAD implantation, depressive symptoms interfered with this improvement. Further studies are needed to determine whether psychological interventions for depression, in addition to EBCR, would improve the response to EBCR after LVAD implantation.

Aerobic Threshold Identification in a Cardiac Disease Population Based on Correlation Properties of Heart Rate Variability.

An index of heart rate (HR) variability correlation properties, the short-term scaling exponent alpha1 of detrended fluctuation analysis (DFA a1) has shown potential to delineate the first ventilatory threshold (VT1). This study aims to extend this concept to a group of participants with cardiac disease. Sixteen volunteers with stable coronary disease or heart failure performed an incremental cycling ramp to exhaustion PRE and POST a 3-week training intervention. Oxygen uptake (VO2) and HR at VT1 were obtained from a metabolic cart. An ECG was processed for DFA a1 and HR. The HR variability threshold (HRVT) was defined as the VO2, HR or power where DFA a1 reached a value of 0.75. Mean VT1 was reached at 16.82 ± 5.72 mL/kg/min, HR of 91.3 ± 11.9 bpm and power of 67.8 ± 17.9 watts compared to HRVT at 18.02 ± 7.74 mL/kg/min, HR of 94.7 ± 14.2 bpm and power of 73.2 ± 25.0 watts. Linear relationships were seen between modalities, with Pearson’s r of 0.95 (VO2), 0.86 (HR) and 0.87 (power). Bland–Altman assessment showed mean differences of 1.20 mL/kg/min, 3.4 bpm and 5.4 watts. Mean peak VO2 and VT1 did not change after training intervention. However, the correlation between PRE to POST change in VO2 at VT1 with the change in VO2 at HRVT was significant (r = 0.84, p < 0.001). Reaching a DFA a1 of 0.75 was associated with the VT1 in a population with cardiac disease. VT1 change after training intervention followed that of the HRVT, confirming the relationship between these parameters.

Terahertz bandstop-to-bandpass converter based on VO2 hybrid metasurface

We experimentally demonstrated a terahertz (THz) bandstop-to-bandpass converter based on vanadium dioxide (VO2) hybrid metasurface. The unit cell consists of gold and VO2 hybrid structures standing on a high resistance silicon substrate. Simulation and experimental results show that for y-polarized waves, the device’s function converts from bandstop filtering to bandpass filtering when VO2 transits from insulating state to metallic state induced by the Joule heat produced by the heating wire on the surface. The operation principle is explained by combining the surface current distribution and the LC equivalent circuit model. For x-polarized waves, when VO2 changes from insulating state to metallic state, the response of the device to THz wave changes from single resonant state to double resonant state. This phenomenon originates from the conductance coupling effect in plasma optics. The proposed device realizes active control of THz waves and is expected to be used in the fields of THz communication, imaging and electromagnetic switching.

Predictors for one-year outcomes of cardiorespiratory fitness and cardiovascular risk factor control after cardiac rehabilitation in elderly patients: The EU-CaRE study.

Studies on effectiveness of cardiac rehabilitation (CR) in elderly cardiovascular disease patients are rare, and it is unknown, which patients benefit most. We aimed to identify predictors for 1-year outcomes of cardiorespiratory fitness and CV risk factor (CVRF) control in patients after completing CR programs offered across seven European countries. Cardiovascular disease patients with minimal age 65 years who participated in comprehensive CR were included in this observational study. Peak oxygen uptake (VO2), body mass index (BMI), resting systolic blood pressure (BPsys), and low-density lipoprotein-cholesterol (LDL-C) were assessed before CR (T0), at termination of CR (T1), and 12 months after start of CR (T2). Predictors for changes were identified by multivariate regression models. Data was available from 1241 out of 1633 EU-CaRE patients. The strongest predictor for improvement in peak VO2 was open chest surgery, with a nearly four-fold increase in surgery compared to non-surgery patients. In patients after surgery, age, female sex, physical inactivity and time from index event to T0 were negative predictors for improvement in peak VO2. In patients without surgery, previous acute coronary syndrome and higher exercise capacity at T0 were the only negative predictors. Neither number of attended training sessions nor duration of CR were significantly associated with change in peak VO2. Non-surgery patients were more likely to achieve risk factor targets (BPsys, LDL-C, BMI) than surgery patients. In a previously understudied population of elderly CR patients, time between index event and start of CR in surgery and disease severity in non-surgery patients were the most important predictors for long-term improvement of peak VO2. Non-surgery patients had better CVRF control.