Matthew P. Wallen

Accuracy of Heart Rate Watches: Implications for Weight Management

Background Wrist-worn monitors claim to provide accurate measures of heart rate and energy expenditure. People wishing to lose weight use these devices to monitor energy balance, however the accuracy of these devices to measure such parameters has not been established. Aim To determine the accuracy of four wrist-worn devices (Apple Watch, Fitbit Charge HR, Samsung Gear S and Mio Alpha) to measure heart rate and energy expenditure at rest and during exercise. Methods Twenty-two healthy volunteers (50% female; aged 24 ± 5.6 years) completed ~1-hr protocols involving supine and seated rest, walking and running on a treadmill and cycling on an ergometer. Data from the devices collected during the protocol were compared with reference methods: electrocardiography (heart rate) and indirect calorimetry (energy expenditure). Results None of the devices performed significantly better overall, however heart rate was consistently more accurate than energy expenditure across all four devices. Correlations between the devices and reference methods were moderate to strong for heart rate (0.67–0.95 [0.35 to 0.98]) and weak to strong for energy expenditure (0.16–0.86 [-0.25 to 0.95]). All devices underestimated both outcomes compared to reference methods. The percentage error for heart rate was small across the devices (range: 1–9%) but greater for energy expenditure (9–43%). Similarly, limits of agreement were considerably narrower for heart rate (ranging from -27.3 to 13.1 bpm) than energy expenditure (ranging from -266.7 to 65.7 kcals) across devices. Conclusion These devices accurately measure heart rate. However, estimates of energy expenditure are poor and would have implications for people using these devices for weight loss.

NAFLD in clinical practice: Can simple blood and anthropometric markers be used to detect change in liver fat measured by 1 H-MRS?

Research in NAFLD management is commonly based on quantitative assessment of liver fat by proton‐magnetic resonance spectroscopy (1H‐MRS), and translation of this into clinical practice is currently limited by availability and expense. Novel steatosis biomarkers have been proposed for the prediction of liver fatness; however, whether these are suitable for detecting changes in liver fat is unknown. We aimed to determine the accuracy of these indices, and waist circumference (WC), in quantifying longitudinal change in 1H‐MRS‐quantified liver fat.

Impact of beta-blockers on cardiopulmonary exercise testing in patients with advanced liver disease

Patients with advanced liver disease may develop portal hypertension that can result in variceal haemorrhage. Beta‐blockers reduce portal pressure and minimise haemorrhage risk. These medications may attenuate measures of cardiopulmonary performance, such as the ventilatory threshold and peak oxygen uptake measured via cardiopulmonary exercise testing.

Safety, adherence and efficacy of exercise training in solid-organ transplant candidates: A systematic review

BACKGROUND Patients awaiting solid-organ transplantation may be encouraged to undertake exercise training to improve pre- and post-transplant outcomes. However, the safety, adherence and efficacy of exercise training in this population remain unclear. METHODS All randomized, non-randomized and non-controlled trials of exercise training interventions in solid-organ transplant candidates were included. The Cochrane risk of bias tool and a modified Newcastle-Ottawa scale were used to assess procedural quality. Safety was defined as the number of reported adverse events during exercise training. Adherence was evaluated from session attendance, and efficacy as changes in cardiorespiratory fitness (CRF), exercise capacity, muscular strength, health-related quality of life (HR-QoL) and lung function. RESULTS Eleven studies involving 874 patients were included: four randomized controlled, one non-randomized controlled and six non-controlled trials. Six studies included heart transplant candidates and five involved patients awaiting lung transplantation. Three trials included aerobic-only training, one incorporated resistance-only exercise and seven combined modalities. Twelve adverse events were reported with four due to exercise, although methods to collect these data were often omitted. Exercise adherence ranged from 82.5% to 100%, but was poorly described. No significant between-group changes attributable to exercise training were demonstrated. However, significant within-group improvements in CRF, exercise capacity, muscular strength, lung function and HR-QoL were observed. CONCLUSIONS Patients awaiting heart or lung transplant appear to tolerate exercise training despite the larger number of adverse events compared to other high-risk populations. Exercise training demonstrated within-group benefits for several outcomes, with no significant between-group differences. Randomized controlled trials with sufficient statistical power are required for all solid-organ transplant candidates.

Assessment of the 5-Minute Oxygen Uptake Efficiency Slope in Children With Obesity

PURPOSE Poor cardiorespiratory fitness is associated with increased all cause morbidity and mortality. In children with obesity, maximum oxygen uptake (V̇O2max) may not be achieved due to reduced motivation and peripheral fatigue. We aimed to identify a valid submaximal surrogate for V̇O2max in children with obesity. METHOD Ninety-two children with obesity (7-16 years) completed a maximal exercise treadmill test and entered a three-month exercise and/or nutrition intervention after which the exercise test was repeated (n = 63). Participants were required to reach V̇O2max to be included in this analysis (n = 32 at baseline and n = 13 at both time-points). The oxygen uptake efficiency slope (OUES) was determined as the slope of the line when V̇O2 (L/min) was plotted against log V̇E. Associations between the maximal OUES, submaximal OUES (at 3, 4, 5 and 6 min of the exercise test) and V̇O2max were calculated. RESULTS In the cross-sectional analysis, V̇O2max (L/min) was strongly correlated with 5-min OUES independent of Tanner puberty stage and sex (R2 = .80, p < .001). Longitudinal changes in V̇O2max were closely reflected by changes in 5-min OUES independent of change in percent body fat (R2 = .63, p < .05). CONCLUSION The 5-min OUES is a viable alternative to V̇O2max when assessing children with obesity.

High-intensity interval training and cardiac autonomic control in individuals with metabolic syndrome: A randomised trial

BACKGROUND Insulin resistance has been postulated to play a central role in the co-appearance of various cardiovascular disease risk factors constituting the metabolic syndrome (MetS). There is evidence that altered cardiac autonomic function (CAF) may precede the onset of insulin resistance. Exercise training has been shown to improve CAF in different populations, yet little is known regarding the exercise dose response for CAF. The aim of this study was to investigate the impact of different volumes of high-intensity interval training (HIIT) and traditional moderate-intensity continuous training (MICT) on CAF in participants with MetS. METHODS Individuals with MetS (n=56) were randomised into the following 16-week training interventions: i) MICT (n=16, 30min at 60-70%HRpeak, 5×/week); ii) 4HIIT (n=19, 4×4min bouts at 85-95%HRpeak, interspersed with 3min of active recovery at 50-70%HRpeak, 3×/week); or iii) 1HIIT (n=21, 1×4min bout at 85-95%HRpeak, 3×/week). R-R interval recorded for 5min in a supine position at pre- and post-intervention was used to derive linear (SDNN, RMSSD, pNN50, LF, HF, LF/HF) and non-linear (SD1, SD2, Alpha1, Alpha2, SampEn) heart rate variability (HRV) indices as measures of CAF. Group×time interaction effects were examined (ANCOVA) and Eta squared (η2) interaction effect sizes calculated. RESULTS While there were no significant between-group differences in CAF indices, there were small-to-medium group×time interaction effects on SDNN [F(2,52)=0.70, p=0.50, η2=0.02], RMSSD [F(2,52)=1.35, p=0.27, η2=0.03], HF power [F(2,52)=1.27, p=0.29, η2=0.03], SD1 [F(2,52)=0.47, p=0.63, η2=0.01], and SD2 [F(2,52)=0.41, p=0.67, η2=0.01]. The following represent the relative percentage increases across these variables for 4HIIT, MICT, and 1HIIT respectively (SDNN, +30%, +17%, 9%; RMSSD, +30%, +22%, -2%; HF power, +69%, +18%, +7%; SD1, +30%, +22%,-2%; SD2, +22%, +14%, 4%). CONCLUSIONS There were no significant between-group differences for the effects of exercise dose on CAF indices, however; high-volume HIIT demonstrated the greatest magnitude of effect for improving CAF in individuals with MetS.

Neoadjuvant therapy reduces cardiopulmunary function in patients undegoing oesophagectomy

Neoadjuvant therapy (NAT) for oesophageal cancer may reduce cardiopulmonary function, assessed by cardiopulmonary exercise testing (CPEX). Impaired cardiopulmonary function is associated with mortality following esophagectomy. We sought to assess the impact of NAT on cardiopulmonary function using CPEX and assessing the clinical relevance of any change in particular if changes were associated with post-operative morbidity. This was a prospective, cohort study of 40 patients in whom CPEX was performed before and after NAT. Thirty-eight patients underwent surgery and follow-up with perioperative outcomes measured. The primary variables derived from CPEX were the anaerobic threshold (AT) and peak oxygen uptake (V˙O2peak). There were significant reductions in the AT (pre-NAT: 12.4 ± 3.0 vs. post-NAT 10.6 ± 2.0 mL kg-1.min-1; p = 0.001). This reduction was also evident for V˙O2peak (pre-NAT: 16.6 ± 3.6 vs. post-NAT 14.9 ± 3.7 mL kg-1.min-1; p = 0.004). The relative reduction in V˙O2peak was greater in chemotherapy patients who developed any peri-operative morbidity (p = 0.04). For patients who underwent chemoradiotherapy, there was a significantly greater relative reduction in AT (p = 0.03) for those who encountered a respiratory complication. Cardiopulmonary function significantly declined as a result of NAT prior to oesophagectomy. The reduction in AT and V˙O2peak was similar in both the chemotherapy and chemoradiotherapy groups.

Changes in dietary patterns and body composition within 12 months of liver transplantation

Background Cardiometabolic risk factors are increasing in liver transplant recipients (LTR). Influencing dietary factors have not been assessed. The aim of this observational study was to assess changes in weight, metabolic function, dietary intake and eating behaviours in the first year after orthotopic liver transplantation (OLT). Methods Consecutive recruitment of 17 patients (14 males) awaiting OLT at a single tertiary hospital. Dietary intake, food behaviours and anthropometry were recorded at baseline, and 6 and 12 months post-transplant. Results By 12 months, patients had gained on average 7.3% of body weight. The prevalence of overweight or obesity increased from baseline 53% to 77% (P=0.001). By 6 months, 65% (n=11/17) of patients had altered glucose metabolism. Dietary intake was consistent with a Western-style dietary pattern with high saturated fat. Over half of the patients (69%, n=11/16) reported low to no depressive feelings and rated their self-esteem as good (53%, n=9/16). The Power of Food Scale increased between pre and post-transplant, indicating a stronger appetitive drive. Conclusions Weight gain occurs early post-transplant, with significant metabolic dysfunction present within 6 months, however is not associated with significant psychological distress. Early dietary intervention designed to limit weight gain and target cardiometabolic health is recommended for this unique patient population.

Ultrasound muscle thickness for the bedside assessment of sarcopenia in patients with cirrhosis

Background: Interferon gamma release assay (IGRA) is the most widely used test for screening of latent tuberculosis (TB). However, indeterminate IGRA tests may occur, reducing the utility of the test, and have been associated with impaired immune status. The performance of the IGRA in patients with end stage liver disease, a disease state with known, multifaceted immune dysfunction, has not been well studied. The aim of this study was therefore to evaluate the prevalence and predictors of indeterminate IGRAs in patients with end stage liver disease being assessed for liver transplantation. Methods: Prospective study of 49 consecutive patients undergoing liver transplantation assessment who underwent IGRA (Quantiferon-TB Gold) to exclude latent TB. Groups (indeterminate versus determinate) were compared and tested for association with clinically relevant variables (age, aetiology of liver disease, MELD score, Child–Pugh score and absolute lymphocyte count). Groups were compared using the Mann–Whitney U-test. Testing for independent associations with an indeterminate test was performed using multivariate logistic regression. An ROC curve was also created to define the optimum probability cut off. Results: Of the 49 IGRAs performed, 12 (24%) were indeterminate and 37 (76%) were determinate. Of the determinate IGRAs, three (6 %) were positive and 34 (70%) were negative. Patients who had an indeterminate test were significantly older than those with determinate tests (57.3 vs. 50.5, p = 0.03). There were no other statistically significant differences between the indeterminate versus determinate group: mean MELD score (16.1 vs. 15.8, p = 0.43), mean Child–Pugh score (9.8 vs. 8.8, p = 0.21), mean absolute lymphocyte count (1.03 vs. 0.95, p = 0.30). Multivariate logistic regression testing for independent associations with an indeterminate test, together with changes in the area under the ROC curve, are shown in Table 1. The combination of these variables could provide a high degree of accuracy for predicting an indeterminate test with a c statistic of 0.80 for the ROC curve (Fig. 1). Conclusions: Patients with advanced liver disease had a high rate of indeterminate IGRA in this study relative to other groups described in the literature, which may limit the utility of this test in this population. Indeterminate tests could be predicted with moderate to high accuracy using five routinely collected clinical variables. The reason for the high prevalence of indeterminate tests may relate to immune dysfunction associated with advanced liver disease but results require validation in larger studies.