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J Am Coll Cardiol, 2006; 47:1835-1839, doi:10.1016/j.jacc.2005.12.050
(Published online 17 April 2006). © 2006 by the American College of Cardiology Foundation |
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* Cardiovascular Medicine Department, CNR Institute of Clinical Physiology, Pisa, Italy
Scuba Superiore S. Anna, Pisa, Italy
G. da Saliceto Hospital, Piacenza, Italy.
Manuscript received September 21, 2005; revised manuscript received December 5, 2005, accepted December 13, 2005.
* Reprint requests and correspondence: Dr. Claudio Passino, CNR Institute of Clinical Physiology, Via Moruzzi 1, 56124 Pisa, Italy. (Email: passino{at}ifc.cnr.it).
| Abstract |
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BACKGROUND: Patients with HF benefit from physical training. Chronic neurohormonal activation has detrimental effects on ventricular remodeling and prognosis of patients with HF.
METHODS: A total of 95 patients with HF were assigned randomly into two groups: 47 patients (group T) underwent a nine-month training program at 60% of the maximal oxygen uptake (VO2), whereas 48 patients did not (group C). The exercise load was adjusted during follow-up to achieve a progressive training effect. Plasma assay of B-type natriuretic peptide (BNP), amino-terminal pro-brain natriuretic peptide (NT-proBNP), norepinephrine, plasma renin activity, and aldosterone; quality-of-life questionnaire; echocardiogram; and cardiopulmonary stress test were performed upon enrollment and at the third and ninth month.
RESULTS: A total of 85 patients completed the protocol (44 in group T, left ventricular ejection fraction [EF] 35 ± 2%, mean ± SEM; and 41 in group C, EF 32 ± 2%, p = NS). At the ninth month, patients who underwent training showed an improvement in workload (+14%, p < 0.001), peak VO2 (+13%, p < 0.001), systolic function (EF +9%, p < 0.01), and quality of life. We noted that BNP, NT-proBNP, and norepinephrine values decreased after training (34%, p < 0.01; 32%, p < 0.05; 26%, p < 0.01, respectively). Increase in peak VO2 with training correlated significantly with the decrease in both BNP/NT-proBNP level (p < 0.001 and p < 0.01, respectively). Patients who did not undergo training showed no changes.
CONCLUSIONS: Clinical benefits after physical training in patients with HF are associated with blunting of adrenergic overactivity and of natriuretic peptide overexpression.
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Neurohormonal activation is a hallmark of HF (7). The production of B-type natriuretic peptide (BNP) by ventricular cardiomyocytes correlates with left ventricular dysfunction (8,9). Thus, the assay of either BNP or amino-terminal pro-brain natriuretic peptide (NT-proBNP) has been proposed as diagnostic and prognostic tool (9). However, studies concerning the influence of training on BNP secretion early after myocardial infarction (10) and in patients with chronic HF (11,12) have given conflicting results. In this study, we evaluated the effect of home-based aerobic physical training, with adjustment of the exercise load during follow-up for achieving a progressive training effect, on neurohormonal activation in patients in HF.
| Methods |
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Patients underwent neurohormonal and clinical evaluation and a maximal exercise test with gas exchange (cardiopulmonary stress test [CPT]) within the same morning upon enrollment and at the third and ninth month. An echocardiographic study was performed, and patients rated their QOL on entry and at the end of the study.
Physical training. The training program consisted of cycling on a bike for a minimum of 3 days per week, 30 min per day. Patients were instructed to exercise at 60 rpm, keeping heart rate constantly monitored at 65% of peak VO2 heart rate, by a wearable device. At the enrollment, they participated to in-hospital training sessions. Their compliance to the program was checked by a physiotherapist and at the first, second, third, sixth, and ninth month. At the third-month visit, workload was adjusted according to a new CPT. Patients in group C underwent follow-up visits at the third and ninth month to exclude changes in their usual lifestyle and physical activity.
Cardiopulmonary exercise test, echocardiographic study, QOL, and plasma assays. A CPT was performed by exercise on a bicycle ergometer using a ramp protocol with increments of 10 W/min. We measured VO2, CO2 production, and minute ventilation using breath-to-breath gas analysis (Vmax, Sensormedics, Conshohocken, Pennsylvania). Peak VO2 (the highest value at end-exercise, as a 20-s average) and ventilatory efficiency on exercise (slope of the ventilation vs. VCO2 relation in its linear part) were determined. The same physician performed all the CPTs and was unaware of the results of blood sampling. The echocardiographic studies were all performed by the same physician.
Quality of life was evaluated by means of the Minnesota Living With Heart Failure Questionnaire; BNP, plasma catecholamines, plasma renin activity, and aldosterone were assayed as described elsewhere (9); and NT-proBNP was measured with an automated electrochemiluminescent immunoassay.
Statistics. Because neurohormone values are not distributed normally, natural logarithmic transformation of data was used for parametric statistical analysis, including two-way repeated-measure analysis of variance, Bonferroni post-hoc test, and linear regression analysis. Skewness and Kurtosis tests were used to determine whether data were normally distributed. Chi-square and unpaired t tests were used to evaluate differences between the two groups. Mauchlys test to assess the sphericity assumption was performed. To assess the significance of the interaction between groups, we applied the Greenhouse-Geisser correction factor when Mauchlys test was significant (13). The results are expressed as mean values ± SEM, and p values were considered significant when < 0.05.
| Results |
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Baseline neurohormones and functional capacity.
As expected, patients from both group T and C showed neurohormonal activation, depressed functional capacity, and a slightly reduced ventilatory efficiency, with no different baseline values (Tables 1 and 2).
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Effects of physical training on left ventricular volumes and function, functional capacity, and QOL. In group T, EF had increased by the nine-month visit, with a reduction in end-diastolic and end-systolic left ventricular volumes (Table 2). Conversely, echocardiographic parameters did not change in group C.
Group T progressively increased tolerance to effort from baseline up to the third and the ninth month (peak VO2 F = 10.35, p < 0.001, and maximum workload F = 13.26, p < 0.001) (Fig. 1). Resting heart rate decreased by the end of the follow-up from 75 ± 2 beats/min to 69 ± 2 beats/min (p = 0.002). No changes were found in these parameters in group C (Fig. 1). By the end of follow-up, VE/VCO2 slope did not change in either of the two groups, and only patients in group T showed an improvement in their QOL (score from 54 ± 5 to 32 ± 4 in group T, p < 0.01; from 52 ± 6 to 53 ± 5 in group C, p = NS).
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| Discussion |
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Previous studies have demonstrated that training improves cardiac function, peak oxygen uptake, and QOL (26,11,12). However, long-term training programs performed with a constant intensity of exercise do not seem to guarantee a continuous improvement in functional capacity (4). Conversely, a workload adjusted according to the third-month CPT produced a progressive increase in peak VO2, paralleled by a progressive decrease in neurohormone level in the present study.
The lack of improvement of the VE/VCO2 slope could be ascribed to the quite-preserved exercise capacity and ventilatory efficiency in our population (Table 2) as compared with a previous study (14). The reduction in plasma BNP/NT-proBNP in group T might be an expression of improved cardiac systolic function (8), sympathetic deactivation (12), and improvement in tissue oxygenation (15). The decrease in plasma norepinephrine level might be explained by the positive modulation of the autonomic balance by physical training (3).
Study limitations. A control group of healthy subjects was not included because it is unlikely that training could affect their BNP/NT-proBNP plasma levels under physiologic conditions (8). Furthermore, women accounted for only 15% of the patients, a figure which reflects the female prevalence of larger HF studies, among which the ExtraMATCH meta-analysis on training in HF (6).
Conclusions. The BNP/NT-proBNP and norepinephrine plasma values progressively decrease after training, paralleling functional and clinical improvement. The present findings suggest the usefulness of the BNP/NT-proBNP assay as an effective tool for the follow-up of patients with HF undergoing physical training.
| Acknowledgments |
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| References |
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