Relation of respiratory muscle strength, cachexia and survival in severe chronic heart failure

Background Respiratory muscle (RM) function predicts prognosis in non‐cachectic patients with chronic heart failure (CHF). We hypothesized that weakness of RM (maximum inspiratory mouth occlusion pressure, Pi max ) is a function of body mass index, and that outcome is more a function of BMI than of Pi max or ventilatory drive (P0.1). Subjects and methods We enrolled 249 CHF patients (11.2 % female, median age 54.2 years) at the German Heart Institute Berlin. Patients were in NYHA classes I/II/III/IV by n  = 16/90/108/35. All patients underwent tests of pulmonary function, RM (Pi max , P0.1), cardiopulmonary exercise testing (peakVO2, VE/VCO2‐slope), and right heart catheterization. Results Mean follow‐up time was 18 (1–36) months, 47 patients (18.9 %) died or underwent cardiac assist implantation. Pi max correlated weakly with BMI ( r  = 0.19), peakVO2 ( r  = 0.15), and FEV1 ( r  = 0.34, all p  < 0.02), and was lower in females compared to males (3.9 ± 1.7 vs. 6.6 ± 2.7 kPa; p  < 0.001). P0.1 correlated with pulmonary pressure (rho = 0.2; p  < 0.01) and peakVO2 (rho = −0.14; p  < 0.02). Neither Pi max [hazard ratio (HR) 0.98; confidence interval (CI) 0.88–1.08] nor P0.1 (HR 0.52; 0.06–4.6) predicted survival. Multivariate regression analysis revealed gender, BMI, and FEV1 as cofactors of Pi max , with only BMI (HR 0.87; CI 0.80–0.95) predicting survival independently. The lowest quintile in BMI had the worst outcome (log‐rank χ ² = 13.5, p  = 0.009). Summary In CHF patients including cachexia and NYHA IV, Pi max does not predict survival. Pi max depends on gender, BMI, FEV1, and peakVO2, with only BMI and peakVO2 predicting survival. The impaired Pi max in CHF might be a result of catabolism and weight loss and is not a predictive factor in itself.