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RESEARCH PRODUCT

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

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Background: 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. Methods and Results: 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 (beta coefficient = 0.01, 95% confidence interval -0.01 to 0.03, P = .241) and pp-peak VO2 ([3 coefficient = -0.00, 95% confidence interval -0.10 to 0.10, P = .975). Conclusions: In symptomatic elderly patients with HFpEF, we found that pp-MIP was not associated with either peak VO2 or pp-peak VO2.