Impairment of Ventilatory Efficiency in Heart Failure

BACKGROUND: Impairment of ventilatory efficiency in congestive heart failure (CHF) correlates well with symptomatology and contributes importantly to dyspnea. METHODS AND RESULTS: We investigated 142 CHF patients (mean NYHA class, 2.6; mean maximum oxygen consumption VO(2)max, 15.3 mL O(2) x kg(-1) x min(-1); mean left ventricular ejection fraction LVEF, 27%). Patients were compared with 101 healthy control subjects. Cardiopulmonary exercise testing was performed, and ventilatory efficiency was defined as the slope of the linear relationship of V(CO(2)) and ventilation (VE). Results are presented in percent of age- and sex-adjusted mean values. Forty-four events (37 deaths and 7 instances of heart transplantation, cardiomyoplasty, or left ventricular assist device implantation) occurred. Among VO(2)max, NYHA class, LVEF, total lung capacity, and age, the most powerful predictor of event-free survival was the VE versus V(CO(2)) slope; patients with a slope 130% (54.7%; P<0.001). CONCLUSIONS: The VE versus V(CO(2)) slope is an excellent prognostic parameter. It is easier to obtain than parameters of maximal exercise capacity and is of higher prognostic importance than VO(2)max.