Respiratory muscle dysfunction in congestive heart failure: clinical correlation and prognostic significance

Abstract

Background: In congestive heart failure (CHF), the prognostic significance of impaired respiratory muscle strength has not been established.

Methods and results: Maximal inspiratory pressure (Pi(max)) was prospectively determined in 244 consecutive patients (207 men) with CHF (ischemic, n=75; idiopathic dilated cardiomyopathy, n=169; age, 54+/-11 years; left ventricular 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+/-16 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 curves 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); multivariate analyses also included NYHA functional class, LVEF, peak oxygen consumption (peak VO(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 VO(2) (area under the curve [AUC], 0.68 versus 0.73; P=0.28), and they improved with the triple combination of Pi(max), peak VO(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 and emerges as a novel, independent predictor of prognosis. Because testing for Pi(max) is simple in clinical practice, it might serve as an additional factor to improve risk stratification and patient selection for cardiac transplantation.