The Role of Inspiratory Muscle Strength in Functional Capacity and Left Atrial Strain in Patients With Heart Failure With Mildly Reduced and Preserved Ejection Fraction

ABSTRACT Objectives This study aimed to explore the correlation among inspiratory muscle strength, left atrial strain reservoir (LAsr), and functional capacity in patients with heart failure with preserved and mildly reduced ejection fractions (HFpEF and HFmrEF). Methods This cross‐sectional study enrolled 40 patients with HFpEF and HFmrEF. Regression analyses were conducted at both univariate and multivariate levels to explore the relationships between maximal inspiratory pressure (MIP), peak oxygen consumption (pVO 2 ), six‐minute walk distance (6MWD), and LAsr. Results MIP significantly correlated with pVO 2 ( r = 0.400, p = 0.011) and 6MWD ( r = 0.549, p < 0.001) in univariate analyses, with multivariable regression confirming its independent association with pVO 2 ( β = 0.07, 95% CI: 0.02–0.14, p = 0.044) and 6MWD ( β = 1.14, 95% CI: 0.04–2.23, p = 0.043). While univariate analysis showed a meaningful correlation between MIP and LArs ( r = 0.364, p = 0.021), this was not notable in the multivariable model ( β = 0.09, 95% CI: −0.05–0.24, p = 0.181). Conclusions MIP is a significant predictor of exercise capacity in HFpEF and HFmrEF; however, its relationship with LAsr was influenced by confounding factors. It is essential to address inspiratory muscle weakness for effective management of patients with HFpEF and HFmrEF. Trial Registration This trial was registered in the Thai Clinical Trials Registry ( https://www.thaiclinicaltrials.org/ ) under the trial ID TCTR20231121001.