Ventilatory power: A novel index that enhances prognostic assessment of patients with heart failure

Abstract

Background: Minute ventilation/CO2 production (VE/VCO 2) slope is an index determined by cardiopulmonary exercise testing, which incorporates pertinent cardiac, pulmonary, and skeletal muscle physiology into a substantive composite assessment. The VE/VCO2 slope has many applications, including utility as a well-validated prognostic gauge for patients with heart failure (HF). In this study, we combine VE/VCO2 slope with systolic blood pressure, creating a novel index that e labeled ventilatory power. Ventilatory power links the combined physiology inherent in the VE/VCO2 slope to peripheral pressure, adding an additional dimension pertinent to HF assessment. Whereas the related concept of circulatory power links peak oxygen consumption with peak systolic blood pressure as a prognostic index, we hypothesized that ventilatory power would provide greater prognostic discrimination than VE/V CO2 slope, peak oxygen consumption, and circulatory power for patients with systolic HF. Methods and Results: Patients with systolic HF (left ventricular ejection fraction ≤35%) underwent symptom-limited cardiopulmonary exercise testing as part of routine management and were followed for up to 4 years for major cardiac events (mortality, left ventricular assist device implantation, and heart transplantation). Eight hundred seventy-five patients with HF (left ventricular ejection fraction, 26±9%; mean age, 55±14) were studied. Cardiopulmonary exercise testing indices peak oxygen consumption, VE/VCO 2 slope, circulatory power, and ventilatory power were all predictive of cardiac events (P <0.001). Multivariate analysis demonstrated that ventilatory power was the strongest indicator of prognosis. Conclusions: Although circulatory power and traditional cardiopulmonary exercise testing parameters can be used to predict prognosis among patients with HF, ventilatory power provides relatively greater prognostic discrimination and may constitute a relatively more useful composite tool. © 2012 American Heart Association, Inc.