Determinants of Cardiorespiratory Fitness in Patients with Heart Failure Across a Wide Range of Ejection Fractions.

Impaired cardiorespiratory fitness (CRF) in heart failure (HF) is influenced by a complex array of cardiac and extracardiac factors. The study aimed to identify clinical determinants of CRF measured as peak oxygen consumption (peak VO ₂ ) in HF patients, and to determine a peak VO ₂ prediction model using regression equations. Retrospective analysis of 200 HF patients who completed treadmill cardiopulmonary exercise testing and underwent Doppler echocardiography and/or biomarker analysis on the same day was performed. After univariate linear regression analysis, a multivariate peak VO ₂ prediction model was developed using significant variables in a stepwise linear regression analysis. In subjects with repeated testing, Pearson's correlation was used to assess correlations between measured and predicted change in peak VO ₂ (Δpeak VO ₂ ) over time. Mean age was 57 years, with 55% being male. Stepwise linear regression was used to generate a weighted model for peak VO ₂ : 30.895 + (-0.112•age[years]) + (0.296•hemoglobin [g/dl]) + (-0.101•E/e'[unit change]) + (-0.202• body mass index [kg/m ² ]) + (-0.593• N-terminal pro-brain natriuretic peptide [log _N pg/ml])) + (-1.349•CRP [log mg/L]). Predicted peak VO ₂ correlated strongly with measured peak VO ₂ in HF with reduced ejection fraction and HF with preserved ejection fraction patients (r = +0.63, p <0.001; r = +0.64, p <0.001, respectively). Predicted Δpeak VO ₂ correlated with measured Δpeak VO ₂ (r = +0.23, p <0.001). In conclusion, in patients with HF across a wide range of left ventricular ejection fraction, age, systemic inflammation, oxygen carrying capacity, obesity, and elevated filling pressures are the strongest predictors of impaired CRF. The proposed CRF model allows prediction of peak VO ₂ in HF patients and may be used to estimate peak VO ₂ changes over time.
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