Changes in Respiratory Muscle Strength Following Cardiac Rehabilitation for Prognosis in Patients with Heart Failure

Respiratory muscle weakness, frequently observed in patients with heart failure (HF), is reported as a predictor for poor prognosis. Although increased respiratory muscle strength ameliorates exercise tolerance and quality of life in HF patients, the relationship between changes in respiratory muscle strength and patient prognosis remains unclear. A total of 456 patients with HF who continued a 5-month cardiac rehabilitation (CR) were studied. We measured maximal inspiratory pressure (PI_max) at hospital discharge as the baseline and five months thereafter to assess the respiratory muscle strength. Changes in PI_max during the 5-month observation period (⊿PI_max) were examined. We investigated the composite multiple incidence of all-cause death or unplanned readmission after 5-month CR. The relationship between ⊿PI_max and the incidence of clinical events was analyzed. Over a median follow-up of 1.8 years, 221 deaths or readmissions occurred, and their rate of incidence was 4.3/100 person-years. The higher ⊿PI_max was significantly associated with lower incidence of clinical event. In multivariate Poisson regression model after adjustment for clinical confounding factors, ⊿PI_max remained a significant and independent predictor for all-cause death/readmission (adjusted incident rate ratio for ⊿PI_max increase of 10 cmH₂O: 0.77, 95% confidence interval: 0.70-0.86). In conclusion, the changes in respiratory muscle strength independently predict the incidence of clinical events in patients with HF.