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Integration of Brain Tissue Saturation Monitoring in Cardiopulmonary Exercise Testing in Patients with Heart Failure
Published on: October 1, 2019
Usefulness of the predicted percentage ventilatory efficiency for carbon dioxide output during exercise in patients
Kohei Ashikaga1,2,3, Haruki Itoh4, Tomoko Maeda5
1Department of Cardiology, Sakakibara Heart Institute, Fuchu, Tokyo, Japan. k2ashikaga@marianna-u.ac.jp.
Abstract:
The ventilatory efficiency for carbon dioxide output ([Formula: see text]CO2) during exercise, as measured by the minute ventilation vs. [Formula: see text]CO2 slope ([Formula: see text]E vs. [Formula: see text]CO2 slope), is a powerful prognostic index in patients with chronic heart failure (CHF). This measurement is higher in women than in men, and it increases with age. This study aimed to investigate the usefulness of the predicted value of the percentage [Formula: see text]E vs. [Formula: see text]CO2 slope (%[Formula: see text]E vs. [Formula: see text]CO2 slope) as a prognostic index in patients with CHF. A total of 320 patients with CHF and a left ventricular ejection fraction (LVEF) < 45% (male, 85.6%; mean age, 64.6 years) who underwent symptom-limited cardiopulmonary exercise tests using a cycle ergometer were included in the study. The %[Formula: see text]E vs. [Formula: see text]CO2 was calculated using predictive formulae based on age and sex. Cardiovascular-related death was defined as the primary endpoint. The mean follow-up duration was 7.5 ± 3.3 years. Of 101 patients who died during the study period, 75 experienced cardiovascular-related deaths. The average [Formula: see text]E vs. [Formula: see text]CO2 slope was 32.8 ± 8.0, and the average %[Formula: see text]E vs. [Formula: see text]CO2 slope was 119.6 ± 28.2%. The cumulative incidence of cardiovascular-related death after 10 years of follow-up were 44.7% (95% CI 34.4-54.6%) in patients with %[Formula: see text]E vs. [Formula: see text]CO2 slope > 120 and 15.0% (95% CI 9.4-21.8%) in patients with %[Formula: see text]E vs. [Formula: see text]CO2 slope ≤ 120. The multivariate Cox regression analysis indicated that a %[Formula: see text]E vs. [Formula: see text]CO2 slope > 120 was an independent predictor of cardiovascular-related death (adjusted hazard ratio, 3.24; 95% confidence interval 1.65-6.67; p < 0.01). The %[Formula: see text]E vs. [Formula: see text]CO2 slope can be used for risk stratification in patients with CHF and an LVEF < 45%.
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