Author + information
- Received January 19, 2016
- Revision received February 29, 2016
- Accepted March 2, 2016
- Published online June 1, 2016.
- Thomas P. Olson, PhD∗ (, )
- Bruce D. Johnson, PhD and
- Barry A. Borlaug, MD
- ↵∗Reprint requests and correspondence:
Dr. Thomas P. Olson, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, 200 1st Street NW, Joseph 4-225C, Rochester, Minnesota 55905.
Objectives The purpose of this study was to compare measures of gas exchange at rest and during exercise in patients with heart failure and preserved ejection fraction (HFpEF) with age- and sex-matched control subjects.
Background Patients with HFpEF display elevation in left heart pressures, but it is unclear how this affects pulmonary gas transfer or its determinants at rest and during exercise.
Methods Patients with HFpEF (n = 20) and control subjects (n = 26) completed a recumbent cycle ergometry exercise test with simultaneous measurement of ventilation and gas exchange. Diffusion of the lungs for carbon monoxide (DLCO) and its subcomponents, pulmonary capillary blood volume (VC) and alveolar-capillary membrane conductance (DM), were measured at rest, and matched for low-intensity (20 W) and peak exercise. Stroke volume was measured by transthoracic echocardiography to calculate cardiac output.
Results Compared with control subjects, patients with HFpEF displayed impaired diastolic function and reduced exercise capacity. Patients with HFpEF demonstrated a 24% lower DLCO at rest (11.0 ± 2.3 ml/mm Hg/min vs. 14.4 ± 3.3 ml/mm Hg/min; p < 0.01) related to reductions in both DM (18.1 ± 4.9 ml/mm Hg/min vs. 23.1 ± 9.1 ml/mm Hg/min; p = 0.04), and VC (45.9 ± 15.2. ml vs. 58.9 ± 16.2 ml; p = 0.01). DLCO was lower in patients with HFpEF compared with control subjects in all stages of exercise, yet its determinants showed variable responses. With low-level exercise, patients with HFpEF demonstrated greater relative increases in VC, coupled with heightened ventilatory drive and more severe symptoms of dyspnea compared with control subjects. At 20-W exercise, DM was markedly reduced in patients with HFpEF compared with control subjects. From 20 W to peak exercise, there was no further increase in VC in patients with HFpEF, which in tandem with reduced DM, led to a 30% reduction in DLCO at peak exercise (17.3 ± 4.2 ml/mm Hg/min vs. 24.7 ± 7.1 ml/mm Hg/min; p < 0.01).
Conclusions Subjects with HFpEF display altered pulmonary function and gas exchange at rest and especially during exercise, which contributes to exercise intolerance. Novel therapies that improve gas diffusion may be effective to improve exercise tolerance in patients with HFpEF.
Dr. Olson was supported by a grant from the American Heart Association (AHA-12GRNT11630027). Dr. Johnson was supported by NIH grant HL71478. Dr. Borlaug was supported by grants from the Mayo Clinic CTSA, NIH (UL RR024150), and the Marie Ingalls Career Development Award in Cardiovascular Research.
- Received January 19, 2016.
- Revision received February 29, 2016.
- Accepted March 2, 2016.
- American College of Cardiology Foundation