V E / V CO 2 slope is associated with abnormal resting haemodynamics and is a predictor of long-term survival in chronic heart failure
AbstractAbstract Background: Patients with chronic heart failure (CHF) present with exercise-induced hyperpnea, but its pathophysiological mechanism has not been thoroughly investigated. We aimed to determine the relationship between exercise-induced hyperpnea, resting haemodynamic measurements and the validity of ventilatory response ( V E / V CO 2 slope) as a mortality predictor in CHF patients. Methods: Ninety-eight CHF patients (90M/8F) underwent a symptom-limited treadmill cardiopulmonary exercise test (CPET). Right heart catheterization and radionuclide ventriculography were performed within 72 h of CPET. Results: Twenty-seven patients died from cardiac causes during 20±6 months follow-up. Non-survivors had a lower peak oxygen consumption ( V O 2p ), (16.5±4.9 vs. 20.2±6.1, ml/kg/min, p =0.003), a steeper V E / V CO 2 slope (34.8±8.3 vs. 28.9±4.8, p <0.001) and a higher pulmonary capillary wedge pressure (PCWP) (19.5±8.6 vs. 11.7±6.5 mm Hg, p =0.008) than survivors. By multivariate survival analysis, the V E / V CO 2 slope as a continuous variable was an independent prognostic factor ( χ 2 : 8.5, relative risk: 1.1, 95% CI: 1.03–1.18, p =0.004). Overall mortality was 52% in patients with V E / V CO 2 slope ≥34 and 18% in those with V E / V CO 2 slope <34 (log rank: 18.5, p <0.001). In a subgroup of patients ( V O 2 p: 10–18 ml/kg/min), V E / V CO 2 slope was a significant predictor of mortality (relative risk: 6.2, 95% CI: 1.7–22.2, p =0.002). Patients with high V E / V CO 2 slope had higher resting PCWP (19.9±9.1 vs. 11.3±5.7 mmHg, p <0.001) and V E / V CO 2 slope correlated significantly with PCWP ( r : 0.57, p <0.001). Conclusions: The V E / V CO 2 slope, as an index of ventilatory response to exercise, improves the risk stratification of CHF patients. Interstitial pulmonary oedema may be a pathophysiological mechanism of inefficient ventilation during exercise in these patients.