Congestive Heart Failure
Hemodynamic Profile of Submaximal Constant Workload Exercise in Patients With Heart Failure Secondary to Ischemic or Idiopathic Dilated Cardiomyopathy

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Abstract

Constant workload exercise on an upright bicycle at submaximal levels of exercise intensity is frequently used in physical training programs. Nevertheless, only a few data are currently available on the hemodynamic changes induced by constant workload exercise in patients with heart failure. The aim of this study was to assess the hemodynamic response during submaximal constant-workload exercise at 2 different work rates in patients with heart failure. The hemodynamic profile was assessed by means of right-sided cardiac catheterization in 21 men with moderate heart failure during submaximal-constant workload exercise performed on an upright bicycle for 15 minutes. The intensity of constant work rate exercise was selected during a previous symptom-limited or maximal test. The first submaximal test was performed at the level of the anaerobic threshold workload, corresponding to 64% of peak work rate, and the other test at 70% of anaerobic threshold workload (42% of peak work rate). During both submaximal tests, a marked increase in right heart pressure was observed as compared with baseline. The increase in systolic pulmonary artery pressure was statistically not different between the 2 tests (from 40 ± 18 to 66 ± 20 mm Hg during exercise at the anaerobic threshold workload, and from 39 ± 16 to 63 ± 21 mm Hg during exercise under anaerobic threshold). The increase in pulmonary arterial wedge pressure was similar (from 20 ± 10 to 35 ± 13 mm Hg during exercise at the anaerobic threshold, and from 19 ± 9 to 32 ± 12 mm Hg during the other test). Cardiac output and heart rate were significantly higher during submaximal exercise at a higher workload, paralleling the behavior of oxygen uptake. Finally, the hemodynamic profile during submaximal exercise at the anaerobic threshold workload was quite similar to that observed during symptom-limited exercise. Thus, in patients with heart failure, submaximal exercise performed at a constant workload, even at low exercise intensity, may determine relevant pressure changes in pulmonary circulation.

Section snippets

Study Group:

We studied 21 male patients (mean age 59 ± 8 years, range 46 to 72) in sinus rhythm with chronic heart failure of at least 6 months duration caused by left ventricular systolic dysfunction. Mean value of left ventricular ejection fraction was 24 ± 8% (range 13% to 35%), as assessed by means of 2-dimensional echocardiography or radionuclide ventriculography. The etiology of heart failure was coronary artery disease in 12 patients and idiopathic dilated cardiomyopathy in 9. Twelve patients were

Results

Table I lists the hemodynamics in the sitting position before the maximal exercise test and before every submaximal constant-load exercise. The resting hemodynamic profile was similar in the 3 conditions. Table II lists the hemodynamic responses observed during the symptom-limited exercise test.

Discussion

In the last decade, there has been a growing interest in submaximal exercise tests in the functional evaluation of heart failure patients. In these patients, exercise performed at submaximal workload seems to be better tolerated than exercise performed at the maximal workload, and seems to be a more consistent indicator of functional limitation during daily activities, which usually are not symptom-limited. Furthermore, exercise performed at selected submaximal constant work rates represents

Acknowledgements

Acknowledgment:

We are indebted to Marco Pagani for assistance in statistical analysis and Paola Musatti, RN, for extensive support during this study. We also thank Simonetta Scalvini, MD, and Maurizio Volterrani, MD, who cared for patients included in this study, and the patients themselves.

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