Relationship among muscle strength, muscle endurance, and skeletal muscle oxygenation dynamics during ramp incremental cycle exercise.

Peak oxygen uptake (VO2), evaluated as exercise tolerance, is a strong predictor of life prognosis regardless of health condition. Several previous studies have reported that peak VO2 is higher in those with a greater decrease in muscle oxygen saturation (SmO2) in the active muscles during incremental exercise. However, the skeletal muscle characteristics of individuals exhibiting a greater decrease in SmO2 during active muscle engagement in incremental exercise remain unclear. This study aimed to clarify the relationship among muscle strength, muscle endurance, and skeletal muscle oxygenation dynamics in active leg muscles during incremental exercise. Twenty-four healthy young men were included and categorized into the non-moderate-to-high muscular strength and endurance group (those with low leg muscle strength, endurance, or both; n = 11) and the moderate-to-high muscular strength and endurance group (those with both moderate-to-high leg muscle strength and endurance; n = 13). All participants underwent cardiopulmonary exercise testing combined with near-infrared spectroscopy to assess whole-body peak VO2 and the change in SmO2 at the lateral vastus lateralis from rest to each exercise stage as skeletal muscle oxygenation dynamics. A linear mixed-effects model, with the change in SmO2 from rest to each stage as the dependent variable, individual participants as random effects, and group and exercise load as fixed effects, revealed significant main effects for both group (P = 0.001) and exercise load (P < 0.001) as well as a significant interaction between the two factors (P < 0.001). Furthermore, multiple-comparison test results showed that the change in SmO2 from rest to 40%-100% peak VO2 was significantly higher in the moderate-to-high muscular strength and endurance group than in the non-moderate-to-high muscular strength and endurance group. Maintaining both muscle strength and endurance at moderate or higher levels contributes to high skeletal muscle oxygenation dynamics (i.e., greater decrease in SmO2) during moderate- or high-intensity exercise.

Hospital-acquired disability in older heart failure patients decreases independence and increases difficulties in activities of daily living.

AIMS: The aim of this study was to clarify whether worsening of independence in activities of daily living (ADL) and also difficulties in ADL are triggered by hospitalization in older patients with heart failure (HF) and whether difficulties in ADL can predict readmission for HF regardless of independence in ADL in these patients. METHODS AND RESULTS: We enrolled 241 HF patients in the present multi-institutional, prospective, observational study. The patients were divided according to age into the non-older patient group (<75 years, n = 137) and the older patient group (≥75 years, n = 104). The Katz index and the Performance Measure for Activities of Daily Living-8 (PMADL-8) were used to evaluate independence and difficulties in ADL, respectively. The endpoint of this study was rehospitalization for HF. Independence as indicated by the Katz index at discharge was significantly lower than that before admission only in the older patient group, and the value of the PMADL-8 at discharge was significantly higher than that before admission (P < 0.001). In all patients, after adjusting for the Katz index and other variables, PMADL-8 score was a significant predictor of rehospitalization for HF (hazard ratio 1.50; 95% confidence interval 1.07-2.13; P = 0.021). CONCLUSIONS: Worsening of both independence and difficulties in ADL was triggered by hospitalization in older HF patients, and difficulties in ADL were relevant factors for risk of rehospitalization regardless of independence in ADL. These findings indicate the importance of preventing not only decreased independence but also increased difficulties in ADL during and after hospitalization.

Relevant factors of leg strength at hospital discharge in patients hospitalized due to acute decompensated heart failure: multi-institutional prospective observational study.

BACKGROUND: Lower leg strength at hospital discharge is strongly associated with poor prognosis in older patients with acute decompensated heart failure (ADHF). Improving leg strength is important in acute-phase cardiac rehabilitation (CR). AIMS: This study aimed to clarify whether a change in leg strength occurs during hospitalization of older ADHF patients receiving CR and whether it affects leg strength at discharge. METHODS AND RESULTS: We enrolled 247 ADHF patients who underwent CR during hospitalization. They were divided into the non-older patient group (<75 years; n = 142) and older patient group (≥75 years; n = 105). Quadriceps isometric strength (QIS), body mass-corrected QIS (%BM QIS), and change in QIS during hospitalization (QIS ratio) were evaluated in all patients. Physical function in the stable phase was measured by the Performance Measure for Activities of Daily Living-8 (PMADL-8). The QIS value increased during hospitalization in the non-older patient group (30.0 ± 11.1 vs. 31.6 ± 10.9 kgf, P < 0.001) but did not increase in the older patient group (19.1 ± 6.3 vs. 19.5 ± 6.1 kgf, P = 0.275). Multiple regression analysis revealed that PMADL-8 significantly predicted %BM QIS at discharge in the non-older patient group (ß = -0.254, P = 0.004), whereas in the older patient group, QIS ratio and PMADL-8 significantly predicted %BM QIS at discharge (ß = 0.264, P = 0.008 for QIS ratio and ß = -0.307, P = 0.003 for PMADL-8). CONCLUSIONS: Leg strength was not improved in older ADHF patients during hospitalization even if they received CR, and this affected leg strength at discharge, suggesting that careful skeletal muscle intervention should be provided during hospitalization, and patients need to continue exercise after discharge.

New Formula to Predict Heart Rate at Anaerobic Threshold That Considers the Effects of ß-Blockers in Patients With Myocardial Infarction: MULTI-INSTITUTIONAL RETROSPECTIVE CROSS-SECTIONAL STUDY.

PURPOSE: It is recommended that patients with myocardial infarction (MI) be prescribed exercise by target heart rate (HR) at the anaerobic threshold (AT) via cardiopulmonary exercise testing (CPX). Although percent HR reserve using predicted HRmax (%HRRpred) is used to prescribe exercise if CPX or an exercise test cannot be performed, %HRRpred is especially difficult to use when patients take ß-blockers. We devised a new formula to predict HR at AT (HRAT) that considers ß-blocker effects in MI patients and validated its accuracy. METHODS: The new formula was created using the data of 196 MI patients in our hospital (derivation sample), and its accuracy was assessed using the data of 71 MI patients in other hospitals (validation sample). All patients underwent CPX 1 mo after MI onset, and resting HR, resting systolic blood pressure (SBP), and HRAT were measured during CPX. RESULTS: The results of multiple regression analysis in the derivation sample gave the following formula (R2 = 0.605, P < .001): predicted HRAT = 2.035 × (≥65 yr:-1, <65 yr:1) + 3.648 × (body mass index <18.5 kg/m2:-1, body mass index ≥18.5 kg/m2:1) + 4.284 × (ß1-blocker(+):-1, ß1-blocker(-):1) + 0.734 × (HRrest) + 0.078 × (SBPrest) + 36.812. This formula consists entirely of predictors that can be obtained at rest. HRAT and predicted HRAT with the new formula were not significantly different in the validation sample (mean absolute error: 5.5 ± 4.1 bpm). CONCLUSIONS: The accuracy of the new formula appeared to be favorable. This new formula may be a practical method for exercise prescription in MI patients, regardless of their ß-blocker treatment status, if CPX is unavailable.

Effects of αß-Blocker Versus ß1-Blocker Treatment on Heart Rate Response During Incremental Cardiopulmonary Exercise in Japanese Male Patients with Subacute Myocardial Infarction.

A simplified substitute for heart rate (HR) at the anaerobic threshold (AT), i.e., resting HR plus 30 beats per minute or a percentage of predicted maximum HR, is used as a way to determine exercise intensity without cardiopulmonary exercise testing (CPX) data. However, difficulties arise when using this method in subacute myocardial infarction (MI) patients undergoing beta-blocker therapy. This study compared the effects of αß-blocker and ß1-blocker treatment to clarify how different beta blockers affect HR response during incremental exercise. MI patients were divided into αß-blocker (n = 67), ß1-blocker (n = 17), and no-ß-blocker (n = 47) groups. All patients underwent CPX one month after MI onset. The metabolic chronotropic relationship (MCR) was calculated as an indicator of HR response from the ratio of estimated HR to measured HR at AT (MCR-AT) and peak exercise (MCR-peak). MCR-AT and MCR-peak were significantly higher in the αß-blocker group than in the ß1-blocker group (p < 0.001, respectively). Multiple regression analysis revealed that ß1-blocker but not αß-blocker treatment significantly predicted lower MCR-AT and MCR-peak (ß = -0.432, p < 0.001; ß = -0.473, p < 0.001, respectively). Based on these results, when using the simplified method, exercise intensity should be prescribed according to the type of beta blocker used.

Effect of carvedilol on heart rate response to cardiopulmonary exercise up to the anaerobic threshold in patients with subacute myocardial infarction.

Resting heart rate (HR) plus 20 or 30 beats per minute (bpm), i.e., a simplified substitute for HR at the anaerobic threshold (AT), is used as a tool for exercise prescription without cardiopulmonary exercise testing data. While resting HR plus 20 bpm is recommended for patients undergoing beta-blocker therapy, the effects of specific beta blockers on HR response to exercise up to the AT (ΔAT HR) in patients with subacute myocardial infarction (MI) are unclear. This study examined whether carvedilol treatment affects ΔAT HR in subacute MI patients. MI patients were divided into two age- and sex-matched groups [carvedilol (+), n = 66; carvedilol (-), n = 66]. All patients underwent cardiopulmonary exercise testing at 1 month after MI onset. ΔAT HR was calculated by subtracting resting HR from HR at AT. ΔAT HR did not differ significantly between the carvedilol (+) and carvedilol (-) groups (35.64 ± 9.65 vs. 34.67 ± 11.68, P = 0.604). Multiple regression analysis revealed that old age and heart failure after MI were significant predictors of lower ΔAT HR (P = 0.039 and P = 0.013, respectively), but not carvedilol treatment. Our results indicate that carvedilol treatment does not affect ΔAT HR in subacute MI patients. Therefore, exercise prescription based on HR plus 30 bpm may be feasible in this patient population, regardless of carvedilol use, without gas-exchange analysis data.

Soluble Fms-like tyrosine kinase 1 is a novel predictor of brain natriuretic peptide elevation.

Soluble fms-like tyrosine kinase 1 (sFlt-1) is an endogenous inhibitor of vascular endothelial growth factor, which is involved in cardiovascular remodeling and atherosclerosis development. To examine the predictive role of sFlt-1 levels in patients with asymptomatic heart failure, we measured circulating sFlt-1 in patients with or without coronary artery disease (CAD). We analyzed 88 Japanese patients with CAD or patients at high risk for atherosclerosis and who were undergoing total risk management for cardiovascular disease prevention. Circulating sFlt-1 levels correlated with the increase in plasma brain natriuretic peptide levels (ΔBNP) from baseline to the observed levels 5 years later in CAD patients, patients with previous myocardial infarction, and men. ΔBNP levels correlated with sFlt-1 levels in the high-sFlt-1 patients with CAD (r = 0.511, P < 0.01). In all patients, end-systolic volume index (ΔESVI) increased in correlation with a decrease in left ventricular ejection fraction (ΔEF) in the long-term observation, independent of their history of myocardial infarction (ΔESVI = 2.5 mL/m(2) increase/year). Baseline level of sFlt-1 was independent of ΔESVI or ΔEF. The present 5-year observational study demonstrated that high sFlt-1 levels predicted moderate increases in BNP levels in CAD patients. Moreover, ΔBNP was correlated with ΔESVI/year in CAD patients with high-sFlt-1 levels. These data suggest that high sFlt-1 levels may be an effective biomarker to predict the progression of heart failure in patients with CAD.

Circulating interleukin-18: A specific biomarker for atherosclerosis-prone patients with metabolic syndrome.

BACKGROUND: Metabolic syndrome (MetS) is associated with an increased risk of the development of atherosclerotic cardiovascular disease (CVD). Interleukin-18 (IL-18), which is a pleiotropic proinflammatory cytokine with important regulatory functions in the innate immune response system, plays a crucial role in vascular pathologies. IL-18 is also a predictor of cardiovascular death in patients with CVD and is involved in atherosclerotic plaque destabilization. RESULTS: In order to determine if circulating levels of IL-18 can serve as a specific biomarker for distinguishing MetS patients from pre-MetS subjects, we studied 78 patients with visceral fat deposition and 14 age-matched control subjects. Increased levels of IL-18 were observed more frequently in patients with MetS than in pre-MetS subjects and were positively associated with waist circumference. Serum levels of IL-18 were significantly reduced by a change in weight caused by lifestyle modifications. There was a significant interaction between waist circumference and serum IL-18 concentration. Weight loss of at least 5% of the body weight caused by lifestyle modification decreased IL-18 circulating levels relative to the reduction in waist circumference and blood pressure, suggesting that this degree of weight loss benefits the cardiovascular system. CONCLUSION: IL-18 may be a useful biomarker of the clinical manifestations of MetS and for the management of the risk factors of CVD.