Respiratory muscle dysfunction in congestive heart failure - Clinical correlation and prognostic significance

Background-In congestive heart failure (CHF), the prognostic significance o f impaired respiratory muscle strength has not been established. Methods and Results-Maximal inspiratory pressure (Pi(max)) was prospectivel y determined in 244 consecutive patients (207 men) with CHF (ischemic, n=75 ; idiopathic dilated cardiomyopathy, n=169; age, 54 +/- 11 years; left vent ricular ejection fraction [LVEF], 22 +/- 10%). Pi(max) was lower in the 244 patients with CHF than in 25 control subjects (7.6 +/-3.3 versus 10.5 +/-3 .7 kPa; P=0.001). The 57 patients (23%) who died during follow-up (23 +/- 1 6 months; range, 1 to 48 months) had an even more reduced Pi(max) (6.3 +/-3 .2 versus 8.1 +/-3.2 kPa in survivors; P=0.001). Kaplan-Meier survival curv es differentiated between patients subdivided according to quartiles for Pi (max) (P=0.014). Pi(max) was a strong risk predictor in both univariate (P= 0.001) and multivariate Cox proportional hazard analyses (P=0.03); multivar iate analyses also included NYHA functional class, LVEF, peak oxygen consum ption (peak (V) over dot O-2), and norepinephrine plasma concentration. The areas under the receiver-operating characteristic curves for prediction of 1-year survival were comparable for Pi(max) and peak (V) over dot O-2 (are a under the curve [AUC], 0.68 versus 0.73; P=0.28), and they improved with the triple combination of Pi(max), peak (V) over dot O-2, and LVEF (AUC, 0. 82; P=0.004 compared with AUC of Pi(max)). Conclusions-In patients with CHF, inspiratory muscle strength is reduced an d emerges as a novel, independent predictor of prognosis. Because testing f or Pi(max) is simple in clinical practice, it might serve as an additional factor to improve risk stratification and patient selection for cardiac tra nsplantation.