Impairment of Ventilatory Efficiency in Heart Failure

Abstract

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 [V̇ o 2 max], 15.3 mL O 2 · kg −1 · 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 V̇ 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 V̇ o 2 max, NYHA class, LVEF, total lung capacity, and age, the most powerful predictor of event-free survival was the VE versus V̇ co 2 slope; patients with a slope ≤130% of age- and sex-adjusted normal values had a significantly better 1-year event-free survival (88.3%) than patients with a slope >130% (54.7%; P <0.001). Conclusions —The VE versus V̇ 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 V̇ o 2 max.