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 /

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

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 /