Influence of upright exercise on pulmonary hemodynamics in left heart failure

Studies in severe chronic stable heart failure (HF) indicate that pulmonary resistance might remain unchanged during exercise and could subsequently contribute to limitation in exercise capacity of these patients. We assessed the possible role of the exercise decreases in mixed venous oxygen tension on this phenomenon in fifteen patients with chronic congestive heart failure (N.Y.H.A. functional classes II to IV) who underwent a symptom-limited treadmill exercise test with hemodynamic monitoring as well as repeated arterial and mixed venous blood gas analysis. For all patients there was an increase in cardiac output (from 3.7 +/- 0.2 to 6.7 +/- 0.5 l/min, p less than 0.001) and pulmonary wedge pressure (from 16 +/- 2 to 31 +/- 3 mm Hg, p less than 0.001) along with exercise with highly significant decrease in total systemic resistance and no significant (from 25.6 +/- 1.5 to 15.8 +/- 1.0 U, p less than 0.001) changes in pulmonary vascular resistances. Arterial blood oxygen tension increased from 86 +/- 3 to 99 +/- 3 mm Hg (p less than 0.001) and mixed venous oxygen tension (PvO2) decreased from 33 +/- 1 to 22 +/- 1 mm Hg (p less than 0.001). Changes in pulmonary vascular resistance during exercise were inversely related to changes in PvO2 (r = -0.61; p less than 0.05). We conclude that the observed decrease in PvO2 might be a determinant of unchanged pulmonary vascular resistance during treadmill-exercise test in severe heart failure patients.