Clinical InvestigationReduced Rate of Alveolar-Capillary Recruitment and Fall of Pulmonary Diffusing Capacity During Exercise in Patients With Heart Failure
Section snippets
Subjects
Nineteen individuals, 11 with stable CHF and 8 controls served as study subjects. For CHF subjects, entry criteria included chronic CHF with stable medical therapy for more than 60 days, New York Heart Association class II or III symptoms, left ventricular ejection fraction < 30%, and no history of clinically significant arrhythmia, pacemaker therapy, or significant anemia (hemoglobin < 11). Control subjects were age- and gender-matched healthy individuals not engaged in regular exercise.
All
Subject Characteristics
Comparison of subject characteristics demonstrated no differences between groups for age, gender, height, and weight (Table 1). Rest cardiac index was lower for the CHF group compared to controls (P < .05). The majority of CHF subjects were New York Heart Association class III with mean left ventricular ejection fraction of 24%. CHF subjects had restrictive pulmonary function compared with controls (Table 1).
Ventilatory, Cardiac, and Metabolic Responses to Exercise
Peak for the initial maximal exercise study was 65% and 116% of predicted for CHF
Discussion
The novel findings of this study are that subjects with stable, chronic CHF demonstrate a reduced rate of rise of DLco during high-intensity constant workload exercise and may also demonstrate a plateau and fall of DLco near end-exercise. In the study described herein, in 8 of 11 CHF subjects, there was a fall of DLco at end-exercise which ranged from 3% to 17%; in the remaining 3 subjects, DLco increased at end-exercise. For the entire CHF group (n = 11), the mean decrease of DLco from
Conclusion
This study confirms previous reports of reduced DLco at rest in patients with CHF8, 16, 17, 18 and extends previous observations to alterations of DLco during high-intensity exercise in CHF subjects, demonstrating both a reduced rate of rise and a decline of DLco near end-exercise consistent with reduced alveolar-capillary recruitment. These observations may be attributed to decreased DLco from chronically reduced DM with a further acute fall of DLco near end-exercise consistent with
Acknowledgments
The authors thank Kathy O'Malley for assistance with data collection, Michelle Small for manuscript preparation and the study volunteers. The authors also acknowledge the staff of the General Clinic Research Center (GCRC) for support throughout this study.
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Supported by NIH grants R01-HL71478 and MO1-RR00585, as well as grants from Mayo Foundation and the American Heart Association.