The impact of preload reduction with head-up tilt testing on longitudinal and transverse left ventricular mechanics.

BACKGROUND: Left ventricular (LV) function is dependent on load, intrinsic contractility and relaxation with a variable impact on specific mechanics. Strain (ε) imaging allows the assessment of cardiac function however the direct relationship between volume and strain is currently unknown. The aim of this study was to establish the impact of preload reduction through head-up tilt (HUT) testing on simultaneous left ventricular (LV) longitudinal and transverse function and their respective contribution to volume change. METHODS: A focused transthoracic echocardiogram was performed on 10 healthy male participants (23 ± 3 years,) in the supine position and following 1 min and 5 min of HUT testing. Raw temporal longitudinal ε (Ls) and transverse ε (Ts) values were exported and divided into 5% increments across the cardiac cycle and corresponding LV volumes were traced at each 5% increment. This provided simultaneous LV longitudinal and transverse ε and volume-loops (deformation-volume analysis - DVA). RESULTS: There was a leftward- shift of the ε -volume loop from supine to 1 min and 5 min of HUT, p<0.001). Moreover, longitudinal shortening was reduced (p<0.001) with a concomitant increase in transverse thickening from supine to 1min, which was further augmented at 5min (p=0.018). CONCLUSIONS: Preload reduction occurs within 1 minute of HUT but does not further reduce at 5 minutes. This decline is associated with a decrease in longitudinal ε and concomitant increase in transverse ε. Consequently, augmented transverse relaxation appears to be an important factor in the maintenance of LV filling in the setting of reduced preload. DVA provides information on the relative contribution of mechanics to a change in LV volume and may have a role in the assessment of clinical populations

Influence of different dynamic sporting disciplines on right ventricular Structure and function in elite male athletes.

Our objective was to assess the influence of different levels of exposure to dynamic training on right ventricular (RV) structure, function and mechanics in elite male athletes. We recruited 492 male elite athletes aged between 18 and 30 years old. Athletes were grouped according to their sporting discipline using the Mitchell Classification as Low Dynamic (LD), Moderate Dynamic (MD) or High Dynamic (HD). All participants underwent 2D, Doppler, tissue Doppler and strain (ε) echocardiography with a focused and comprehensive assessment of the right heart. Athletes involved in MD sports had the largest absolute RV chamber size and when scaled to body size RVOT PLAX, RVOT2, RVD1 and RVD3 were larger in HD compared to MD and LD athletes. There were no between group differences in conventional RV functional indices as well as global RV ε (LD: - 23.4 ± 3.1 vs. MD: - 22.7 ± 2.7 vs. HD: - 23.5 ± 2.6, %) and strain rate (P > 0.01). The base to apex ε gradient in the RV septum was lower in the MD athletes compared to HD and LD due to a lower apical septal ε which significantly correlated with absolute RV chamber size. After scaling for body size there was evidence of larger RV cavities in both MD and HD athletes compared to LD athletes. Global RV function, ε and strain rate were not different between groups. MD athletes had lower apical septal ε that contributed to a smaller base-to-apex ε gradient that is partially associated with larger absolute RV chamber dimensions

An Assessment of the Hydration Status of Recreational Endurance Athletes during Mountain Marathon Events.

Changes in hydration status have been shown to have deleterious effects on physiological functioning, physical performance, mental decision making, and subjective sensation of effort. This exploratory study assessed the hydration status of athletes taking part in mountain marathon events and the implications on performance, cognition and well-being markers. Twenty-nine male recreational athletes from the Original Mountain Marathon (OMM) and nineteen from the Longmynd Hike (LH) provided urine samples before, at mid-point (in the OMM) and after the events. Body mass; reaction time tests; and subjective ratings of well-being and effort were also collected/performed at these time points. Post-urine specific gravity (Usg) values [(OMM: 1.023 (range: 1.008 – 1.038) g/ml; LH: 1.024 (range: 1.014 – 1.035) g/ml] were significantly higher than pre-values [(OMM: 1.013 (range: 1.002 – 1.026) g/ml; LH: 1.013 (range: 1.002 – 1.026) g/ml] in both events (p 0.05). There was no association between hydration status and overall performance in the LH, whilst change in Usg from pre- to mid-event was positively associated with performance in the OMM (r = .561, p = 0.004). Whilst no associations were observed between hydration status and reaction time, rate of perceived exertion and subjective ratings of nausea showed positive associations with Usg. These findings suggest that although changes in hydration status of this level may not significantly affect performance, they can impact on participant sensations of effort and well-being

Histological evidence for reversible cardiomyocyte changes and serum cardiac troponin T elevation after exercise in rats.

This study characterized cardiac troponin T (cTnT) appearance and associated histological evidence of reversible or irreversible changes in myocardial ultrastructure, determined via electron microscopy, in rats undertaking isoproterenol (ISO) infusion or an endurance exercise challenge. Male rats were randomized into ISO and exercise groups. In ISO trials rats were killed 5 h (ISO-5H) and 24 h (ISO-REC19H) after a single ISO or saline injection (SAL-5H; SAL-REC19H). In the exercise trials rats were killed before, as a control (EXE-CON), immediately after (EXE-END5H) and 19 h after (EXE-REC19H) a 5-h bout of swimming with 5% body weight attached to their tail. Serum cTnT was quantified by electrochemiluminescence, and myocardial samples in ISO-REC19H, EXE-REC19H and SAL-REC19H were harvested for assessment of specific mitochondrial injury scores using electron-microscopy. cTnT was undetectable in all control animals (SAL-5H/SAL-REC19H and EXE-CON). cTnT increased in all animals after ISO and exercise but the response was significantly higher (P < 0.05) at ISO-5H (median [range]: 2.60 [1.76-6.18] μg · L(-1)) than at EXE-END5H (median [range]: 0.05 [0.02-0.14] μg · L(-1)). cTnT returned to baseline at EXE-REC19H, but had not completely recovered at ISO-REC19H (median [range]: 0.17 [0.09-1.22] μg · L(-1)). Mitochondrial "injury scores" were significantly higher (P < 0.05) in ISO-REC19H compared to EXE-REC19H and SAL-REC19H, with no difference between EXE-REC19H and SAL-REC19H. Mitochondria from EXE-REC19H appeared aggregated in nonlinear clusters in a small number of scans. These findings suggest that acute exercise-induced appearance of cTnT in this animal model is only associated with reversible changes in cardiomyocyte structure

Reproducibility and feasibility of right ventricular strain and strain rate (SR) as determined by myocardial speckle tracking during high-intensity upright exercise: a comparison with tissue Doppler-derived strain and SR in healthy human hearts.

This study aimed to establish feasibility for myocardial speckle tracking (MST) and intra-observer reliability of both MST and tissue velocity imaging (TVI)-derived right ventricular (RV) strain (ϵ) and strain rate (SR) at rest and during upright incremental exercise. RV ϵ and SR were derived using both techniques in 19 healthy male participants. MST-derived ϵ and SR were feasible at rest (85% of segments tracked appropriately). Feasibility reduced significantly with progressive exercise intensity (3% of segments tracking appropriately at 90% maximum heart rate (HRmax)). Coefficient of variations (CoVs) of global ϵ values at rest was acceptable for both TVI and MST (7-12%), with low bias and narrow limits of agreement. Global SR data were less reliable for MST compared with TVI as demonstrated with CoV data (systolic SR=15 and 61%, early diastolic SR=16 and 17% and late diastolic SR=26 and 31% respectively). CoVs of global RV ϵ and SR obtained at 50% HRmax were acceptable using both techniques. As exercise intensity increased to 70 and 90% HRmax, reliability of ϵ and SR values reduced with larger variability in MST. We conclude that RV global and regional ϵ and SR data are feasible, comparable and reliable at rest and at 50% HRmax using both MST and TVI. Reliability was reduced during higher exercise intensities with only TVI acceptable for clinical and scientific use

Macronutrient Consumption Prior to, and During, Mountain Marathon Events

Participation in ultra-endurance events such as mountain marathons is increasing, yet analysis of the nutritional intake and requirements of this group of athletes have received relatively little attention. This field study examined athletes’ food intake prior to, and during a mountain marathon event to assess compliance with recommendations and to identify associations with performance. Nineteen male athletes competing in the Longmynd Hike (LH) completed a 7-day food diary in the week prior to the event and a weighed food inventory of all items consumed during the event. Despite reported intentions to increase carbohydrate (CHO) consumption in the week prior to the event, there was no significant change in consumption across the week. The mean daily CHO intake of 4.5 g/kg/d was below that recommended to effectively enhance glycogen stores. CHO and energy consumption prior to the event were positively associated with performance [energy (kJ/kg/d): r = .56, p = 0.03; CHO (g/kg/d): r = .54, p = 0.04]. Energy and CHO consumption during the event were also positively correlated with performance [energy (kJ/kg/h): r = .80, p < 0.001; CHO (g/kg/h): r = .75, p = 0.001)], despite most participants again failing to meet recommendations for intake. Further research is needed to determine reasons for non-compliance with nutritional guidelines and to investigate to what extent type and timing of macronutrient intake during such events impacts on performance

Exploratory assessment of left ventricular strain-volume loops in severe aortic valve diseases.

Objectives The purpose of this study was to examine left ventricular (LV) strain (ԑ)-volume loops to provide novel insight into the haemodynamic cardiac consequences of aortic valve stenosis (AS) and aortic valve regurgitation (AR). Methods 27 participants were retrospectively recruited: AR (n = 7), AS (n = 10) and controls (n = 10). Standard transthoracic echocardiography was utilised to obtain apical 4 chamber images to construct ԑ-volume relationships were assessed by: Early systolic ԑ (ԑ_ES), slope of ԑ-volume relation during systole (Sslope), End-systolic peak ԑ (peak ԑ), Diastolic uncoupling (systolic ԑ-diastolic ԑ at same volume) during early diastole (UNCOUP_ED) and late diastole (UNCOUP_LD). ROC-curves were used to determine the ability to detect impaired LV function. Results Whilst LV ejection fraction was comparable between groups, longitudinal peak ԑ was similarly reduced compared to controls. In contrast, ԑ_ES and Sslope were lower in both pathologies compared to controls (P  0.05) to distinguish AS vs Controls, AR vs Controls and AS vs AR, respectively. Conclusions Temporal changes in ԑ-volume characteristics provide novel insight into the haemodynamic cardiac impact of AS and AR. Contrary to traditional measures (i.e. ejection fraction, peak ԑ), these novel measures successfully distinguish between the haemodynamic cardiac impact of AS and AR. This article is protected by copyright. All rights reserved

Left ventricular function and mechanics following prolonged endurance exercise: an update and meta-analysis with insights from novel techniques.

BACKGROUND: The cardiac consequences of undertaking endurance exercise are the topic of recent debate. The purpose of this review is to provide an update on a growing body of literature, focusing on left ventricular (LV) function following prolonged endurance exercise over 2 h in duration which have employed novel techniques, including myocardial speckle tracking, to provide a more comprehensive global and regional assessment of LV mechanics. METHODS: Prospective studies were filtered independently following a pre-set criteria, resulting in the inclusion of 27 studies in the analyses. A random-effects meta-analysis was used to determine the weighted mean difference and 95% confidence intervals (CI) of LV functional and mechanical data from pre-to-post-exercise. Narrative commentary was also provided where volume of available evidence precluded meta-analysis. RESULTS: A significant overall reduction in LV longitudinal strain (Ɛ) n = 22 (- 18 ± 1 to - 17 ± 1%; effect size (d) - 9: - 1 to - 0.5%), strain rate n = 10 (SR; d - 0.9: - 0.1.3 to - 0.5 l/s) and twist n = 5 (11.9 ± 2.2 to 8.7 ± 2.2°, d - 1: - 1.6 to - 0.3°) was observed following strenuous endurance exercise (range 120-1740 min) (P  0.05). CONCLUSION: The meta-analysis and narrative commentary demonstrated that a reduction in LV function and mechanics is evident following prolonged endurance exercise. The mechanism(s) responsible for these changes are complex and likely multi-factorial in nature and may be linked to right and left ventricular interaction

Impact of prolonged walking exercise on cardiac structure and function in cardiac patients versus healthy controls.

BACKGROUND AND DESIGN: Previous studies have demonstrated that endurance exercise can cause an acute transient decrease in cardiac function in healthy subjects. Whether this also occurs in cardiac patients is unknown. We investigated the impact of prolonged single day and three-day walking exercise on cardiac function and cardiac biomarkers between cardiac patients and healthy controls in an observational study. METHODS: We recruited 10 cardiac patients (nine males, one female, 68 ± 5 years) and 10 age- and sex-matched healthy control subjects (nine males, one female, 68 ± 4 years) to perform 30 or 40 km of walking exercise per day for three consecutive days. Cardiac function was examined using echocardiography and cardiac biomarkers (cardiac troponin and B-type natriuretic peptide) with blood samples. Data were collected before walking and directly after walking on day 1 and day 3. RESULTS: Post-exercise early systolic tissue contraction velocity of the left ventricle (p = 0.005) and global longitudinal left ventricle strain (P = 0.026) were increased in both groups compared with baseline. Post-exercise right ventricle peak early diastolic tissue filling velocity and systolic blood pressure/left ventricle end-systolic volume ratio decreased in both groups (p = 0.043 and p = 0.028, respectively). Post-exercise cardiac troponin levels increased (p = 0.045) but did not differ across groups (p = 0.60), whereas B-type natriuretic peptide levels did not change (p = 0.43). CONCLUSION: This study suggests that stable cardiac patients are capable of performing three days of prolonged walking exercise without clinically significant acute overall deterioration in cardiac function or more pronounced increase in cardiac biomarkers compared with healthy controls

Holographic fabrication of 3D photonic crystals using silicon based reflective optics element

We present a silicon based single optical element that is able to automatically generate desired laser beam polarizations and intensities for the holographic fabrication of woodpile-type photonic crystal templates. A polydimethylsiloxane (PDMS) mold based reflective optics element is fabricated for the generation of five-beam interferences where four beams are arranged four-fold symmetrically around a central beam. Silicon chips in the inner surfaces of the mold are used to reflect the circularly or elliptically polarized beam into four side beams that are linearly polarized with electric fields normal to the incident plane, and reduce their laser intensities. Photonic crystal templates are holographically fabricated in a photosensitive polymer through this silicon-on-PDMS based single optical element and single beam based configuration. © 2012 Optical Society of America