Comparing methods for prescribing exercise for individuals with chronic heart failure

This study examined the accuracy of current recommended guidelines for prescribing exercise intensity using the methods of percentage of heart rate reserve (%HRR), percentage of VO2 peak (%VO2peak) and percentage of VO2 reserve (%VO2R) in a clinical population of chronic heart failure (CHF) patients. The precision of prescription of exercise intensity for 45 patients with stable CHF (39:6 M:F, 65&plusmn;9 yrs (mean&plusmn;SD)) was investigated. VO2peak testing is relatively common among patients with cardiac disease, but the assessment of VO2rest is not common practice and the accepted standard value of 3.5 mL/kg/min is assumed in the application of %VO2R (%VO2R3.5). In this study, VO2rest was recorded for 3 min prior to the start of a symptom-limited exercise test on a cycle ergometer. Target exercise intensities were calculated using the VO2 corresponding to 50 or 80 %HRR, VO2peak and VO2R. The VO2 values were then converted into prescribed speeds on a treadmill in km/hr at 1 %grade using ACSM&rsquo;s metabolic equation for walking. Target intensities and prescribed treadmill speeds were also calculated with the %VO2R method using the mean VO2rest value of participants (3.9 mL/kg/min) (%VO2R3.9). This was then compared to the exercise intensities and prescribed treadmill speeds using patient&rsquo;s measured VO2rest. Error in prescription correlates the difference between %VO2R3.5 and %VO2R3.9 compared to %VO2R with measured VO2rest. Prescription of exercise intensity through the %HRR method is imprecise for patients on medications that blunt the HR response to exercise. %VO2R method offers a significant improvement in exercise prescription compared to %VO2peak. However, a disparity of 10 % still exists in the %VO2R method using the standard 3.5 mL/kg/min for VO2rest in the %VO2R equation. The mean measured VO2rest in the 45 CHF patients was 11 % higher (3.9&plusmn;0.8 mL/kg/min) than the standard value provided by ACSM. Applying the mean measured VO2rest value of 3.9 mL/kg/min rather than the standard assumed value of 3.5 mL/kg/min proved to be closer to the prescribed intensity determined by the actual measured resting VO2. These results suggest that the %HRR method should not be used to prescribe exercise intensity for CHF patients. Instead, VO2 should be used to prescribe exercise intensity and be expressed as %VO2R with measured variables (VO2rest and VO2peak).<br /

Moderate-intensity resistance exercise training in patients with chronic heart failure improves strength, endurance, heart rate variability, and forearm blood flow

Background Resistance exercise training was applied to patients with chronic heart failure (CHF) on the basis that it may partly reverse deficiencies in skeletal muscle strength and endurance, aerobic power (VO2peak), heart rate variability (HRV), and forearm blood flow (FBF) that are all putative factors in the syndrome. Methods and results Thirty-nine CHF patients (New York Heart Association Functional Class = 2.3±0.5; left ventricular ejection fraction 28%±7%; age 65±11 years; 33:6 male:female) underwent 2 identical series of tests, 1 week apart, for strength and endurance of the knee and elbow extensors and flexors, VO2peak, HRV, FBF at rest, and FBF activated by forearm exercise or limb ischemia. Patients were then randomized to 3 months of resistance training (EX, n = 19), consisting of mainly isokinetic (hydraulic) ergometry, interspersed with rest intervals, or continuance with usual care (CON, n = 20), after which they underwent repeat endpoint testing. Combining all 4 movement patterns, strength increased for EX by 21±30% (mean±SD, P<.01) after training, whereas endurance improved 21±21% (P<.01). Corresponding data for CON remained almost unchanged (strength P<.005, endurance P<.003 EX versus CON). VO2peak improved in EX by 11±15% (P<.01), whereas it decreased by 10±18% (P<.05) in CON (P<.001 EX versus CON). The ratio of low-frequency to high-frequency spectral power fell after resistance training in EX by 44±53% (P<.01), but was unchanged in CON (P<.05 EX versus CON). FBF increased at rest by 20±32% (P<.01), and when stimulated by submaximal exercise (24±32%, P<.01) or limb ischemia (26±45%, P<.01) in EX, but not in CON (P<.01 EX versus CON). Conclusions Moderate-intensity resistance exercise training in CHF patients produced favorable changes to skeletal muscle strength and endurance, VO2peak, FBF, and HRV

Reduced exercise tolerance in CHF may be related to factors other than impaired skeletal muscle oxidative capacity

We sought to determine whether skeletal muscle oxidative capacity, fiber type proportions and fiber size, capillary density or muscle mass might explain the impaired exercise tolerance in chronic heart failure (CHF). Previous studies are equivocal regarding the maladaptations that occur in the skeletal muscle of patients with CHF and their role in the observed exercise intolerance. Total body O2 uptake (peak) was determined in 14 CHF patients and 8 healthy sedentary similarly-aged controls. Muscle samples were analysed for mitochondrial ATP production rate (MAPR), oxidative and glycolytic enzyme activity, fiber size and type, and capillary density. CHF patients demonstrated a lower peak (15.1 ± 1.1 vs. 28.1 ± 2.3 ml.kg&VO2&VO2-1.min-1, p<0.001) and capillary to fiber ratio (1.09 ± 0.05 vs. 1.40 ± 0.04; p<0.001) when compared to controls. However there was no difference in capillary density (capillaries per μm2) across any of the fiber types. Measurements of MAPR and oxidative enzyme activity indicated no difference in muscle oxidative capacity between the groups. We find that neither reduced muscle oxidative capacity nor capillary density are the cause of exercise limitation in CHF patients, so that the low VO2 peak observed in CHF patients is the result of muscle fiber atrophy and possibly impaired activation of oxidative phosphorylation

Reliability of isokinetic strength and aerobic power testing for patients with chronic heart failure

PURPOSE: The objective of this study was to assess the reliability of testing skeletal muscle strength and peak aerobic power in a clinical population of patients with chronic heart failure (CHF). METHODS: Thirty-three patients with CHF (New York Heart Association (NYHA) Functional Class 2.3 &plusmn; 0.5; left ventricular ejection fraction 27% &plusmn; 7%; age 65 &plusmn; 9 years; 28:5 male-female ratio) underwent two identical series of tests (T1 and T2), 1 week apart, for strength and endurance of the muscle groups responsible for knee extension/flexion and elbow extension/flexion. The patients also underwent two graded exercise tests on a bicycle ergometer to measure peak oxygen consumption (VO2peak). Three months later, 18 of the patients underwent a third test (T3) for each of the measures. Means were compared using MANOVA with repeated measures for strength and endurance, and ANOVA with repeated measures for VO2peak. RESULTS: Combining data for all four movement patterns, the expression of strength increased from T1 to T2 by 12% &plusmn; 25% (P &lt; .001; intraclass correlation coefficient [ICC] = 0.89). Correspondingly, endurance increased by 13% &plusmn; 23% (P = .004; ICC = 0.87). Peak oxygen consumption was not significantly different (16.2 &plusmn; 0.8 and 16.1 &plusmn; 0.8 mL&middot;kg-1&middot;min-1 for T1 and T2, respectively;P = .686; ICC = 0.91). There were no significant differences between T2 and T3 for strength (2% &plusmn; 17%;P = .736; ICC = 0.92) or muscle endurance (-1% &plusmn; 15%;P = .812; ICC = 0.96), but VO2peak decreased from 16.7 &plusmn; 1.2 to 14.9 &plusmn; 0.9 mL&middot;kg-1&middot;min-1 (-10% &plusmn; 18%;P = .021; ICC = 0.89). CONCLUSIONS: These data suggest that in a population of patients with CHF, a familiarization trial for skeletal muscle strength testing is necessary. Although familiarization is not required for assessing oxygen consumption as a single measurement, VO2peak declined markedly in the 3-month period for which these patients were followed. Internal consistency within patients was high for the second and third strength trials and the first and second tests of VO2peak.<br /

Effect of general anaesthesia on functional outcome in patients with anterior circulation ischaemic stroke having endovascular thrombectomy versus standard care: a meta-analysis of individual patient data

Background: General anaesthesia (GA) during endovascular thrombectomy has been associated with worse patient outcomes in observational studies compared with patients treated without GA. We assessed functional outcome in ischaemic stroke patients with large vessel anterior circulation occlusion undergoing endovascular thrombectomy under GA, versus thrombectomy not under GA (with or without sedation) versus standard care (ie, no thrombectomy), stratified by the use of GA versus standard care. Methods: For this meta-analysis, patient-level data were pooled from all patients included in randomised trials in PuMed published between Jan 1, 2010, and May 31, 2017, that compared endovascular thrombectomy predominantly done with stent retrievers with standard care in anterior circulation ischaemic stroke patients (HERMES Collaboration). The primary outcome was functional outcome assessed by ordinal analysis of the modified Rankin scale (mRS) at 90 days in the GA and non-GA subgroups of patients treated with endovascular therapy versus those patients treated with standard care, adjusted for baseline prognostic variables. To account for between-trial variance we used mixed-effects modelling with a random effect for trials incorporated in all models. Bias was assessed using the Cochrane method. The meta-analysis was prospectively designed, but not registered. Findings: Seven trials were identified by our search; of 1764 patients included in these trials, 871 were allocated to endovascular thrombectomy and 893 were assigned standard care. After exclusion of 74 patients (72 did not undergo the procedure and two had missing data on anaesthetic strategy), 236 (30%) of 797 patients who had endovascular procedures were treated under GA. At baseline, patients receiving GA were younger and had a shorter delay between stroke onset and randomisation but they had similar pre-treatment clinical severity compared with patients who did not have GA. Endovascular thrombectomy improved functional outcome at 3 months both in patients who had GA (adjusted common odds ratio (cOR) 1·52, 95% CI 1·09–2·11, p=0·014) and in those who did not have GA (adjusted cOR 2·33, 95% CI 1·75–3·10, p&lt;0·0001) versus standard care. However, outcomes were significantly better for patients who did not receive GA versus those who received GA (covariate-adjusted cOR 1·53, 95% CI 1·14–2·04, p=0·0044). The risk of bias and variability between studies was assessed to be low. Interpretation: Worse outcomes after endovascular thrombectomy were associated with GA, after adjustment for baseline prognostic variables. These data support avoidance of GA whenever possible. The procedure did, however, remain effective versus standard care in patients treated under GA, indicating that treatment should not be withheld in those who require anaesthesia for medical reasons