Inspiratory Muscle Function and Exercise Capacity in Patients With Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a clinical syndrome characterized by impaired exercise capacity resulting from dyspnea and fatigue. The pathophysiological mechanisms underlying the exercise intolerance in HFpEF are not well established. We sought to evaluate the effects of inspiratory muscle function on exercise tolerance in symptomatic patients with HFpEF.

A total of 74 stable symptomatic patients with HFpEF and New York Heart Association class II-III underwent a cardiopulmonary exercise test between June 2012 and May 2016. Inspiratory muscle weakness was defined as maximum inspiratory pressure (MIP)  <70% of normal predicted values. Pearson correlation coefficient and multivariate linear regression analysis were used to assess the association between percent of predicted MIP (pp-MIP) and maximal exercise capacity [measured by peak oxygen uptake (peak VO₂) and percent of predicted peak VO2 (pp-peak VO₂)]. Thirty-one patients (42%) displayed inspiratory muscle weakness. Mean (standard deviation) age was 72.5 ± 9.1 years, 53% were women, and 35.1% displayed New York Heart Association class III. Mean peak VO₂ and pp-peak VO₂ were 10 ± 2.8 mL•min•kg and 57.3 ± 13.8%, respectively. The median (interquartile range) of pp-MIP was 72% (58%-90%). pp-MIP was not correlated with peak VO₂ (r = -0.047, P = .689) nor pp-peak VO₂ (r = -0.078, P = .509). Furthermore, in multivariable analysis, pp-MIP showed no association with peak VO₂ (β coefficient = 0.01, 95% confidence interval -0.01 to 0.03, P = .241) and pp-peak VO₂ (β coefficient = -0.00, 95% confidence interval -0.10 to 0.10, P = .975).

In symptomatic elderly patients with HFpEF, we found that pp-MIP was not associated with either peak VO₂ or pp-peak VO₂.