Cardiopulmonary determinants of functional capacity in patients with chronic heart failure compared with normals

Patients with chronic heart failure (CHF) are characterized by abnormal gas exchange and ventilatory responses to exercise.

This study compares variables obtained from cardiopulmonary exercise testing in 35 patients with CHF with 35 age- and weight-matched healthy subjects. A second goal was to obtain cardiopulmonary variables measured at ventilatory threshold to distinguish patient changes from those of healthy subjects.

Exercise testing was carried out using bicycle ergometry with ramplike protocol (work rate increments 12.5 W/min). Gas exchange and ventilation were measured breath by breath.

Compared with healthy subjects, the VO2 in patients was lower at identical work rates (p < 0.004) and at ventilatory threshold (p < 0.0001), and the slope of the VO2 curve during incremental exercise was flatter (p < 0.05). With the exception of heart rate, the variables for VO2, VCO2, ventilation, O2 pulse, ventilatory equivalents for O2 and CO2, and VD/VT (physiologic deadspace to tidal volume ratio), as well as lactate differed significantly at identical work rates. With the exception of VD/VT, all cardiopulmonary variables showed significant differences in their slopes during exercise. By means of a discriminant analysis, VCO2 and ventilation proved to be the most distinguishing variables at ventilatory threshold between patients with CHF and healthy subjects.

These results indicate the clinical usefulness of cardiopulmonary exercise testing when assessing functional impairment due to CHF. For treatment evaluation, not only VO2 but also VCO2 and ventilation responses to exercise should be considered.