Archives of Hellenic Medicine

Last update:

24-Apr-2007

Arch Hellen Med, 23(6), November-December 2006, 585-594

ORIGINAL PAPER

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 P. RODITIS,¹ E. TSOLAKIS,² I. VENETSIANAKOS,² I. NANAS,² C. ROUSSOS¹
¹Department of Pulmonary and Critical Care Medicine, Laboratory of Cardiopulmonary Exercise Testing and Rehabilitation, "Evgenidio" Hospital, University of Athens
²Department of Clinical Therapeutics, "Alexandra" Hospital, University of Athens, Athens, Greece

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 V_E/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 V_E/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 V_E/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 V_E/VCO₂=34 and 18% in those with V_E/VCO₂<34 (log rank x2: 18.5, P<0.001). In a subgroup of patients (VO2p: 10-18 mL/kg/min), the V_E/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 V_E/VCO₂ had higher resting PCWP (19.9±9.1 vs 11.3±5.7 mmHg, P<0.001) and V_E/VCO₂ correlated significantly with PCWP (r: 0.57, P<0.001).

CONCLUSIONS The V_E/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.