Pulmonary hypertension and exercise intolerance in patients with heart failure

Objectives This study was undertaken to investigate the relationship between pulmonary hypertension and exercise performance in patients with heart failure. Background The exercise capacity of patients with heart failure is frequently reduced. Pulmonary hypertension may contribute to this exercise intolerance by impairing blood flow through the pulmonary circulation. Method Three hundred twenty patients with heart failure underwent upright treadmill exercise testing with hemodynamic monitoring. The incidence of pulmonary hypertension and the relationship between pulmonary vascular resistance (PVR) and exercise cardiac output and minute oxygen consumption (VO2) were examined. Results Pulmonary vascular resistance was normal (<1.5 Wood Units; Group 1) in 28% of the patients, mildly elevated (1.5 to 2.49 Wood Units; Group 2) in 36%, moderately elevated (2.5 to 3.49 Wood Units; Group 3) in 17% and severely elevated (>3.5 Wood Units; Group 4) in 19%. Increasing PVR was associated with significantly lower peak exercise VO2 (Group 1: 13.9+/-3.7; 2:13.7+/-3.4; 3: 11.8+/-2.4; 4: 11.5+/-2.6 L/min, p<0.01 Groups 3 and 4 vs. 1) and lower peak exercise cardiac output (Group 1: 10.0+/-2.8, 2:9.0+/-3.0; 3: 7.4+/-2.1; 4: 6.3+/-2.0 L/min, p<0.05, Groups 2, 3 and 4 vs. 1). The pulmonary wedge pressure decreased during exercise, consistent with impaired left ventricular filling, in 36% of patients with severe pulmonary hypertension (Group 4) versus only 13% of patients with normal PVR (p<0.01). Conclusions Pulmonary vascular resistance is frequently increased in heart failure and is associated with a reduced cardiac output response to exercise, suggesting that pulmonary hypertension impairs exercise performance in heart failure.