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©2012 Wiley Periodicals, inc.
Exercise training appears to improve peak oxygen consumption (VO2) and quality of life (QOL) in heart failure patients, although disease etiology, patient demographics and medication may alter the rate of adaptation. The authors sought to identify rate of change from baseline in fitness, QOL, and depression following exercise training in a cohort of patients with congestive heart failure. Thirty male systolic heart failure patients (aged 63.8±8.3 years, baseline peak VO2 12.2±4.8 mL/kg/min, left ventricular ejection fraction 28.2±9.4%, New York Heart Association class II/II 22/8) undertook 52 weeks of exercise training, 16 weeks as an outpatient and a further 36 weeks of home exercise. Peak VO2 and QOL was measured using the Minnesota Living With Heart Failure (MLWHF) questionnaire and depression using the Hare-Davis scale. The authors analyzed the rate of change in peak VO2 and MLWHF after grouping patients according to clinical, demographic, and pharmacologic characteristics. Peak VO2 measurements varied over time, with no effect of disease pathology or β-blocker on peak VO2. The rate of change in physical MLWHF score was significantly greater (improved) during 0 to 16 weeks in patients with dilated pathology, but was not significantly affected by β-blocker use or age. The exercise training venue and supervision, or lack thereof, is the major determinant of adaptation to the intervention in heart failure patients, although age, β-adrenergic medication, and heart failure etiology also explain some of the variation in adaptive responses observed.
Exercise training has been shown to elicit improvements in various prognostic measures of congestive heart failure including cardiorespiratory fitness,1 quality of life (QOL),2 cardiac function,3 and neurohormonal markers of disease severity.4,5 Typically, cardiac rehabilitation programs consist of 36 sessions delivered over a 12-week period, but this may yield suboptimal changes in fitness and QOL.6–8 Previous reviews of change in QOL in heart failure patients due to exercise training have suggested change is likely, but the magnitude may be dependent on the duration of the program2,9 and the rate of change varies with each individual patient.4 Previous investigations have suggested that the more disadvantaged or deconditioned the patient is at baseline (eg, elderly, New York Heart Association [NYHA] class III, lowest baseline peak oxygen consumption [VO2], ischemic etiology) the larger the likely improvement.10 This hypothesis resonates with some who may argue that exercise training adaptations may be grossly overestimated11 or at least partially explained by regression to the mean. Other works have suggested reasons for the sizeable variations in exercise training responses, most notably seen in the recent Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) study.12 The explanations given for variations in training responses are suboptimal or β-blocker medication,13 disease pathology (particularly if it is unstable), participant age or disease severity,10 suboptimal compliance or crossover from sedentary control to exercise intervention, baseline depression score,12 exercise program delivery,14,15 and transition from an outpatient to unsupervised home exercise program.6
We sought to identify rate of change from baseline in QOL following exercise training in a cohort of patients with systolic congestive heart failure.
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Our longitudinal study shows that age and disease pathology, but not β-blocker use, may affect the rate of adaptation to exercise training in participants with systolic heart failure. Our findings concur with previous work that has suggested that patients with dilated rather than ischemic cardiomyopathy may experience larger and faster health benefits from exercise training. Furthermore, our work shows that outpatient exercise training programs (0–16 weeks in this study) are effective in effecting change in peak VO2 and QOL; however, transition to home exercise training (16–52 weeks) demonstrated evidence of de-training, although some residual health benefits were observed at 52 weeks.
Our work has suggested the rate of change of peak VO2 is faster in patients younger than 50 years, which appears intuitive. Our work also suggested that there was no difference in rate of change of peak VO2 in dilated vs ischemic cardiomyopathy. Previous work has shown that patients with idiopathic dilated cardiomyopathy have significantly increased peak VO2 and decreased left ventricular dimensions compared with those with coronary artery disease, although no information is available on the rate of change.20 Other work has shown that once patients transitioned from outpatient (0–16 weeks) to home exercise programs (16–52 weeks), changes in peak VO2 plateau or even fall,6,7 and this was the case with our participants, although the 52-week trend in peak VO2 was higher than baseline values.
Our data suggest that the physical, but not emotional, dimension of MLWHF QOL score improved (lower) more rapidly in patients with dilated vs ischemic cardiomyopathy during outpatient training (weeks 0–16). Moreover, these benefits were lost more slowly during home exercise training (0–52 weeks) in patients with dilated cardiomyopathy. There were no noticeable differences in QOL scores between patients who did and did not take β-adrenergenic blockade medication. Previous work has suggested that patients with ischemic cardiomyopathy are likely to exhibit smaller improvements in cardiorespiratory fitness (peak VO2) and QOL than patients with dilated cardiomyopathy.10,20,21 Our work did not elicit any variable that created variation in change in Hare-Davis depression score across both outpatient and home exercise periods. It appears that elevated depression scores are elevated in heart failure patients and that they do follow expected improvements (become lower) with outpatient exercise training that are partially lost during home exercise training. The difference between depression and physical fitness and QOL is that no clinical, medicinal, or demographic characteristic appears to create a variation in the rate or size of the response. The primary limitations of this work are the variation in exercise adherence in the home (16–52 week) part of the study and the small sample size n=30.
The venue and presence or absence of exercise supervision clearly had the greatest bearing on the rate of adaptation to exercise training in heart failure patients. That said, age, β-adrenergic blockade, and disease etiology also produced variations to the rate and magnitude of adaption. These findings have implications for outpatient-based rehabilitation programs that may have a finite capacity to train patients. Perhaps preference should be given to older (>50 years) patients who are not taking β-blockers, but exhibit ischemic, rather than dilated, cardiomyopathy.