Arch Hellen Med, 23(6), November-December 2006, 585-594
Ventilatory response to exercise as an independent predictor of long-term survival in chronic heart failure
D. SAKELLARIOU,1 S. NANAS,1 S. DIMOPOULOS,1 S. KAPSIMALAKOU,1 O. PAPAZACHOU,1
OBJECTIVE Patients with chronic heart failure (CHF) present exercise-induced hyperpnea, but the predictive role of this abnormal ventilatory response in risk stratification and its pathophysiological mechanism have not been thoroughly investigated. The objective of this study was to determine the relationship between exercise hyperpnea and resting hemodynamic measurements and evaluate the validity of VE/VCO2 as a risk predictor in patients with CHF.
METHOD The study included 90 men and 8 women with CHF, who underwent a symptom-limited treadmill cardiopulmonary exercise test (CPET). Right heart catheterization and radionuclide ventriculography were performed within 72 hours of CPET. The follow-up period was 20±6 months.
RESULTS The mean (±SD) left ventricular ejection fraction was 31±12% and the pulmonary capillary wedge pressure (PCWP) was 13.8±7.9 mmHg. Twenty-seven patients died from cardiac causes during follow-up. Non-survivors compared to survivors had a lower peak VO2 (16.5±4.9 vs 20.2±6.1 mL/kg/min, P=0.003), a steeper VE/VCO2 slope (34.8±8.3 vs 28.9±4.8, P<0.001) and a higher PCWP (19.5±8.6 vs 11.7±6.5 mmHg, P=0.008). On multivariate survival analysis, the VE/VCO2 slope was an independent prognostic factor (x2: 20.3, relative risk: 3.2, 95% CI: 1.2-7.2, P=0.007). The overall mortality rate was 52% in patients with VE/VCO2=34 and 18% in those with VE/VCO2<34 (log rank x2: 18.5, P<0.001). In a subgroup of patients (VO2p: 10-18 mL/kg/min), the VE/VCO2 slope was also a significant predictor of mortality (relative risk: 6.2, 95% CI: 1.7-22.2, P=0.002). Patients with high VE/VCO2 had higher resting PCWP (19.9±9.1 vs 11.3±5.7 mmHg, P<0.001) and VE/VCO2 correlated significantly with PCWP (r: 0.57, P<0.001).
CONCLUSIONS The VE/VCO2 slope, as an index of ventilatory response to exercise, sharpens the risk stratification of CHF patients. Interstitial pulmonary edema may be a pathophysiological mechanism of inefficient ventilation during exercise in these patients
Key words: Exercise testing, Heart failure, PCWP, Survival, Ventilatory response.