Chronic heart failure (HF) is commonly associated with inspiratory muscle weakness (IMW). However, few studies have investigated risk factors for IMW in patients with HF and systolic dysfunction (left ventricular ejection fraction (LVEF) ≤ 40%).

This longitudinal study aimed to: (1) analyze whether clinical factors, functional capacity measures, and biomarkers of inflammatory and cardiovascular disease were associated with IMW in patients with HF; (2) to analyze associations between IMW, functional capacity and the outcome death in 36 months of follow-up.

This longitudinal study. Patients with HF, NYHA functional class I-II-III, LVEF ≤ 40% consecutively recruited at a referral cardiac tertiary center were evaluated. At baseline, we evaluated patients regarding clinical data, smoking history, peripheral muscle strength using a dynamometer, functional capacity using the six-minute walk test (6MWT) and treadmill cardiopulmonary test (CPT), quality of life using the Minnesota Living with Heart Failure (MLHF) questionnaire and plasma levels of cardiovascular biomarkers. Through analysis of medical records and phone calls, we followed these patients for 36 months for the main outcome, death. Statistical analysis compared the survivor and death groups using the Wilcoxon test for continuous variables and Fisher's exact test was used for categorical variables. To identify predictors of mortality in these patients, a logistic regression was performed. P values <0.05 were considered significant.

Sixty-nine patients were evaluated. They had 58 ± 10 years, LVEF 30 ± 7% and 71% were male. Six patients died during the 36-month follow-up. Compared with survivors, patients in the death group had lower predicted inspiratory muscle pressure (IMP) (80 ±23 vs 57±22%, p= 0.015), lower oxygen consumption (VO2) at the point of respiratory compensation (20 ± 5 vs 15 ± 1 mL/Kg/min, p= 0.020), higher troponin I plasmatic values (453 (244-596) vs 804 (674-1085) pg/mL, p= 0.022), higher Galectin-3 plasmatic values (1168 (806-2092) vs 2756(2021-6514), p=0.020) and worse quality of life according to the MLHF (p=0.048). Most patients in the death group had IMW (83%), with a significant difference (p=0.018) compared to the survivor group, in which only 31% of patients had IMW. Predicted IMP was the only protective predictor of mortality in these patients (OR 0.958 (0.920 to 0.998), p=0.027).

Predicted IMP proved to be an independent protective predictor of mortality in patients with HF and reduced LVEF.

In physiotherapeutic care for patients with HF and reduced LVEF, the assessment of inspiratory muscle strength and identification of IMW is an important measure to guide conducts and identify the severity of patients.