Forearm blood flow in individuals with CHF and age-matched healthy volunteers : a study and historical review

This study examined forearm blood flow (FBF) in individuals with chronic heart failure (CHF) at rest, moderate exercise, and following limb occlusion. FBF was measured by venous occlusion plethysmography in CHF patients (n = 43) and healthy age-matched volunteers (n = 8) at rest and during exercise consisting of intermittent isometric hand squeezing at 15, 30, and 45% of maximum voluntary contraction (MVC). Peak vasodilatory capacity was also determined following the release of an occluding arm cuff. FBF was lower in CHF patients during exercise and during peak reactive hyperemia (PRH) compared to healthy volunteers, but there was no significant difference between groups at rest. Peak vasodilatory capacity was significantly higher in healthy volunteers than the CHF group ((30.6 &plusmn; 8.6 ml&plusmn;100 mL-1&plusmn;min-1 and 18.3 &plusmn; 6.9 ml&plusmn;100 mL-1&plusmn;min-1, respectively). Local blood flow stimulation in response to exercise or limb occlusion is reduced in individuals with CHF, however, there was no difference in resting flows between the two groups, suggesting vasodilatory medication may restore resting blood flow to healthy values. <br /

A nurse-led up-titration clinic improves chronic heart failure optimization of beta-adrenergic receptor blocking therapy : a randomized controlled trial

BACKGROUND: Beta-adrenergic blockade has been shown to improve left ventricular function, reduce hospital admissions and improve survival in chronic heart failure with reduced ejection fraction (HFrEF), with mortality reduction starting early after beta-adrenergic receptor blocker initiation and being dose-related. The aim of this pilot study was to determine the effectiveness of a nurse-led titration clinic in improving the time required for patients to reach optimal doses of the beta-adrenergic receptor blocking agents. METHOD: We conducted a prospective pilot randomized controlled trial. Twenty eight patients with CHF were randomized to optimisation of beta-adrenergic receptor blocker therapy over six months by either a nurse-led titration (NLT) clinic, led by a nurse specialist with the support of a cardiologist in a CHF clinic, or by their primary care physician (usual care (UC)). The primary endpoint was time to maximal beta-adrenergic receptor blocker dose. The secondary end-point was the proportion of patients reaching the target dose of beta-adrenergic receptor blocker by six months. RESULTS: The patients were predominantly men (72%), age 67 ± 16 years; New York Heart Association (NYHA) functional class I (32%), II (44%) and III (20%); baseline left ventricular ejection fraction 33 ± 10%, and a low mean Charlson co-morbidity score of 2.5 ± 1.4. The time to maximum dose was shorter in the NLT group compared to the UC group (90 ± 14 vs 166 ± 8 days, p < 0.0005). At six months, in the NLT group there were nine patients (82%) on high dose and one patient (9%) on low dose beta-adrenergic receptor blocker compared to the UC group with five (42%) patients reaching maximum dose and five (42%) patients on low dose (p = 0.04). The patients allocated to the NLT group also had significantly less worsening of depression between baseline and six months (p = 0.006). CONCLUSION: A NLT clinic improves optimisation of beta-adrenergic receptor blocker therapy through increasing the proportion of patients reaching maximal dose and facilitating rapid up-titration of beta-adrenergic receptor blocker agents in patients with chronic HFrEF. TRIAL REGISTRATION: Australian Clinical Trials Registry (ACTRN012606000383561)

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 /

Differential response to resistance training in CHF according to ACE genotype

The Angiotensin Converting Enzyme (ACE) gene may influence the risk of heart disease and the response to various forms of exercise training may be at least partly dependent on the ACE genotype. We aimed to determine the effect of ACE genotype on the response to moderate intensity circuit resistance training in chronic heart failure (CHF) patients. Methods: The relationship between ACE genotype and the response to 11 weeks of resistance exercise training was determined in 37 CHF patients (New York Heart Association Functional Class=2.3±0.5; left ventricular ejection fraction 28±7%; age 64±12 years; 32:5 male:female) who were randomised to either resistance exercise (n=19) or inactive control group (n=18). Outcome measures included V˙ O2peak, peak power output and muscle strength and endurance. ACE genotype was determined using standard methods. Results: At baseline, patients who were homozygous for the I allele had higher V˙ O2peak (p=0.02) and peak power (p=0.003) compared to patients who were homozygous for the D allele. Patients with the D allele, who were randomised to resistance training, compared to non-exercising controls, had greater peak power increases (ID pb0.001; DD pb0.001) when compared with patients homozygous for the I allele, who did not improve. No significant genotype-dependent changes were observed in V˙ O2peak, muscle strength, muscle endurance or lactate threshold. Conclusion: ACE genotype may have a role in exercise tolerance in CHF and could also influence the effectiveness of resistance training in this condition

Circuit resistance training in chronic heart failure improves skeletal muscle mitochondrial ATP production rate - a randomised controlled trial

Background. We aimed to determine the role of skeletal muscle mitochondrial ATP production rate (MAPR) in relation to exercise tolerance following resistance training in CHF. Methods and Results. Thirteen CHF patients (NYHA functional class 2.3 ± 0.5; LVEF 26 ± 8%; age 70 ± 8 years) underwent testing for VO2peak, and resting vastus lateralis muscle biopsy. Patients were then randomly allocated to 11 weeks of RT, (n = 7) or continuance of usual care (C, n = 6) following which testing was repeated. Muscle samples were analysed for MAPR, metabolic enzyme activity and capillary density. VO2peak and MAPR in the presence of the pyruvate and malate (P+M) substrate combination, representing carbohydrate metabolism, increased in RT (p<0.05) and decreased in C (p<0.05) with a significant difference between groups (VO2peak p = 0.005; MAPR p = 0.03). There was a strong correlation between the change in MAPR and the change in VO2peak over the study (r = 0.875; p < 0.0001), the change in MAPR accounting for 70% of the change in VO2peak. Conclusions. These findings suggest that mitochondrial ATP production is a major determinant of aerobic capacity in CHF patients and can be favourably altered by muscle trengthening exercise

Effect of Exercise Training on Left Ventricular Remodeling in Diabetic Patients with Diastolic Dysfunction: Rationale and Design

This study will examine the effects of combined aerobic and resistance training on left ventricular remodeling in diabetic patients with diastolic dysfunction. This is the first randomized controlled trial to look for effects of combined strength training and aerobic exercise on myocardial function as well as other clinical, functional, or psychological parameters in diabetic patients with isolated diastolic dysfunction, and will provide important insights into the potential management strategies for heart failure with preserved ejection fraction

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 /

The reliability of the 1RM strength test for untrained middle-aged individuals

The one-repetition maximum (1RM) test is considered the gold standard for assessing muscle strength in non-laboratory situations. Since most previous 1RM reliability studies have been conducted with experienced young participants, it is unclear if acceptable test–retest reliability exists for untrained middle-aged individuals. This study examined the reliability of the 1RM strength test of untrained middle-aged individuals. Fifty-three untrained males (n = 25) and females (n = 28) aged 51.2 ± 0.9 years participated in the study. Participants undertook the first 1RM test (T1) 4–8 days after a familiarisation session with the same exercises. 1RM was assessed for seven different exercises. Four to eight days after T1, participants underwent another identical 1RM test (T2). Ten weeks later, 27 participants underwent a third test (T3). Intraclass correlation coefficients (ICC), typical error as a coefficient of variation (TEcv), retest correlation, repeated measures ANOVA, Bland–Altman plots, and estimation of 95% confidence limits were used to assess reliability. A high ICC (ICC > 0.99) and high correlation (r > 0.9) were found for all exercises. TEcv ranged from 2.2 to 10.1%. No significant change was found for six of the seven exercises between T1 and T2. Leg press was slightly higher at T2 compared to T1 (1.6 ± 0.6%, p = 0.02). No significant change was found between T2 and T3 for any exercise. 1RM is a reliable method of evaluating the maximal strength in untrained middle-aged individuals. It appears that 1RM-testing protocols that include one familiarisation session and one testing session are sufficient for assessing maximal strength in this population