Is serial determination of inspiratory muscle strength a useful prognostic marker in chronic heart failure?
BACKGROUND
Little data exists on the prognostic role of inspiratory muscle strength (PImax) in chronic heart failure (CHF). Training studies, however, frequently use it as a therapeutic target and surrogate marker for prognosis. The prognostic value of changes of PImax that allow this extrapolation is unknown.


METHODS
Patients with stable CHF were prospectively included and 1-year and all-time event rates recorded for endpoint analysis.


METHODS
In 158 patients (85% men; New York Heart Association functional class: 2.4+/-0.6), PImax was measured along with clinical evaluations at two visits, the initial visit and the second visit, 6.4+/-1.4 months apart. The mean follow-up was 59+/-34 months.


RESULTS
Overall, 59 patients (37%) reached the primary endpoint of death or hospitalization (endpoint positive), and overall mortality rate (secondary endpoint) was 26% (42 patients). PImax did not differ between endpoint-negative and endpoint-positive patients, both at the initial and at the second visit (8.3+/-5.6 vs. 7.3+/-3.4 kPa and 8.8+/-6.0 vs. 7.9+/-3.6 kPa, respectively; P=NS), and both groups showed increased PImax (0.6+/-2.6 vs. 0.6+/-2.8 kPa; P=NS). Cox analyses found neither the absolute nor the relative change of PImax to be significant predictors for the primary and secondary endpoints (P=NS for both), both for the 1-year and for the all-time event rates. Endpoint rates did not differ between patients showing increasing or decreasing PImax (P=NS; relative risk (RR): 0.77; 95% confidence interval: 0.47-1.27).


CONCLUSIONS
Trials focusing on inspiratory muscle function should use the actual levels of PImax as a surrogate marker to represent prognostic information, rather than relative or absolute changes. This is the first study to investigate the prognostic information of the changes of PImax over time, regarding both short-term and long-term morbidity and mortality in patients with stable CHF.
Frankenstein
Lutz
L
Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany. Lutz_Frankenstein@med.uni-heidelberg.de
Meyer
Franz Joachim
FJ
Sigg
Caroline
C
Nelles
Manfred
M
Schellberg
Dieter
D
Remppis
Andrew
A
Katus
Hugo A
HA
Zugck
Christian
C
D000328:Adult; D002908:Chronic Disease; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology*; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012132:Respiratory Muscles / Q000503:physiopathology*; D018570:Risk Assessment; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left