Purpose: The objective of this study was to investigate the effect of changes in expiratory intrathoracic pressure on stroke volume (SV) at rest and during moderate exercise in patients with heart failure versus healthy individuals.
Methods: SV was obtained by echocardiography during spontaneous breathing and during expiratory loads of 5 and 10 cm H2O produced by a ventilator in 11 patients with heart failure (61 ± yr, ejection fraction: 32 ± 4%, New York Heart Association, 32% ± 4%; NYHA class I–II) and 11 age-matched healthy individuals at rest and during exercise at 60% of aerobic capacity on a semirecumbent cycle ergometer.
Results: At rest, expiratory loading did not change HR, SV index (SVI), or cardiac index (CI) in either group. During moderate exercise, expiratory loading increased SVI and CI in patients with heart failure but decreased SVI and CI in healthy individuals. There was a negative correlation between changes in gastric pressure and SVI (r = −0.51, P < 0.05) in healthy individuals, whereas there was a positive correlation between changes in gastric pressure accompanying expiratory loading and CI (r = 0.83, P < 0.01) in patients with heart failure.
Conclusion: Expiratory loading during moderate exercise elicited increases in SVI and CI in patients with heart failure but decreased SVI and CI in healthy individuals. Improvements in cardiac function during submaximal exercise in patients with heart failure may be caused by a beneficial reduction in left ventricular preload.
Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN
Address for correspondence: Sophie Lalande, Ph.D., Human Integrative and Environmental Physiology Laboratory, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905; E-mail: email@example.com.
Submitted for publication May 2012.
Accepted for publication June 2012.