Prognostic Significance and Determinants of the 6-Min Walk Test in Patients With Heart Failure and Preserved Ejection Fraction

Objectives: This study sought to define the prognostic significance and clinical determinants of the 6-min walk distance (6-MWD) in affected patients.

Background: Symptoms of exertional fatigue and dyspnea, as well as a reduced exercise tolerance, are cardinal features of pulmonary hypertension associated with heart failure and preserved ejection fraction (PH-HFpEF). Mechanisms limiting exercise capacity in this specific entity remain incompletely understood.

Methods: Consecutive patients with PH-HFpEF, as confirmed by right heart catheter, were enrolled in our prospective registry. Hospitalization for HF and/or death for cardiac reasons were defined as primary outcome. Multiple regression models were constructed to establish determinants of the 6-MWD. For quantification of left ventricular (LV) extracellular matrix (ECM), myocardial biopsies were taken from 18 patients.

Results: Between December 2010 and July 2013, 142 PH-HFpEF patients were included in the study. After a mean follow-up of 14.0 ± 10.0 months, 43 patients (30.3%) reached the combined endpoint. The 6-MWD was found to be an independent predictor of outcome and was influenced by a variety of clinical, echocardiographic, hemodynamic, laboratory, and pulmonary parameters. There was a significant inverse correlation between the 6-MWD and the extent of ECM in the LV myocardium.

Conclusions: Impaired exercise capacity in PH-HFpEF patients is explained by cardiac and noncardiac factors. The 6-MWD predicts outcome and may be a useful endpoint in clinical trials.