Abstract 15103: Inefficient Ventilation is an Easily Derived Marker of Cardiovascular Reserve Capacity in Heart Failure With Preserved Ejection Fraction: A RELAX Trial Ancillary Study
Background: Ventilatory efficiency, assessed by minute ventilation (VE)-carbon dioxide (VCO2) slope, predicts outcome in heart failure (HF). We hypothesized that VE/VCO2 slope is correlated with indicators of secondary pulmonary hypertension (PH) in HF with preserved EF (HFpEF).
Methods: Maximum incremental cardiopulmonary exercise tests (CPET) were performed on 216 subjects with HFpEF in the RELAX study and analyzed at a central CPET laboratory. For each subject, VE/VCO2 slope was calculated from the regression line of VE and VCO2 throughout exercise.
Results: The median (25th, 75th%) VE/VCO2 slope was 32.9 (28.4, 37.5). The relationship between VE and VCO2 was linear throughout exercise (r2≥0.95 in 95% of subjects). VE/VCO2 slope was inversely related to BMI (P<0.001) and directly related to age (P=0.02). After adjusting for age and BMI, VE/VCO2 slope remained significantly related to estimated pulmonary arterial systolic pressure (PASP, Table) , and biomarkers related to increased pulmonary vascular tone (plasma Endothelin 1) and ventricular wall stress (E/e’ and NT-ProBNP). Increasing VE/VCO2 slope was also associated with greater perceived dyspnea during exercise (Borg Score) and lower peak VO2, but not with metrics of pulmonary function (FEV1, oxygen saturation). Change in VE/VCO2 slope over 24 weeks was directly related to changes in NT-ProBNP (P=0.007) and inversely related to changes in peak VO2 (P<0.001). The pulmonary vasodilator sildenafil did not improve VE/VCO2 slope, even in subjects with elevated VE/VCO2 (i.e. >34) at baseline.
Conclusions: In HFpEF, ventilatory efficiency is related to indicators of secondary PH, cardiac wall stress, peak exercise capacity and exertional dyspnea. VE/VCO2 slope is an easily derived marker of cardiovascular reserve capacity from brief low-level exercise that can characterize physiological limitations of patients with HFpEF.
- © 2013 by American Heart Association, Inc.