Development of a ventilatory classification system in patients with heart failure

BACKGROUND - Ventilatory efficiency, commonly assessed by the minute ventilation (V̇E)-carbon dioxide production (V̇CO₂) slope, is a powerful prognostic marker in the heart failure population. The purpose of the present study is to refine the prognostic power of the V̇E/V̇CO ₂ slope by developing a ventilatory class system that correlates V̇E/V̇CO₂ cut points to cardiac-related events. METHODS AND RESULTS - Four hundred forty-eight subjects diagnosed with heart failure were included in this analysis. The V̇E/V̇CO₂ slope was determined via cardiopulmonary exercise testing. Subjects were tracked for major cardiac events (mortality, transplantation, or left ventricular assist device implantation) for 2 years after cardiopulmonary exercise testing. There were 81 cardiac-related events (64 deaths, 10 heart transplants, and 7 left ventricular assist device implantations) during the 2-year tracking period. Receiver operating characteristic curve analysis revealed the overall V̇E/V̇CO₂ slope classification scheme was significant (area under the curve: 0.78 [95% CI, 0.73 to 0.83], P2 slope stratifies the burden of risk for the entire spectrum of heart failure severity. Application of this classification is therefore proposed to improve clinical decision making in heart failure.