Complimentary roles for N-terminal pro-B-type natriuretic peptide and spirometry to assess functional capacity in patients with complex mixed heart valve disease.
BACKGROUND
Assessing the effects of valvular heart disease on functional capacity is important for optimal timing of surgery.


OBJECTIVE
To determine whether N-terminal pro-B type natriuretic peptide (NT-proBNP) and lung spirometry predict maximum oxygen consumption (pVO(2)) on cardio-pulmonary exercise testing in patients with mixed heart valve disease.


METHODS
Forty-five clinically stable patients with moderate-severe stenosis and/or regurgitation of the aortic, mitral and/or tricuspid valves were studied. The ability of echocardiography, NT-proBNP, forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) to predict impaired pVO(2) was determined.


RESULTS
On univariate analysis the natural logarithm of NT-proBNP explained more of the variation in pVO(2) (r(2) = 0.40, p < 0.0001) than valve severity score (r(2) = 0.20, p = 0.002), pulmonary artery pressure (r(2) = 0.21, p = 0.005), left atrial area index (r(2) = 0.25, p = 0.001) or LV ejection fraction (r(2) = 0.02, p = 0.4). Low lean body weight (r(2) = 0.21, p = 0.002), FEV1 (r(2) = 0.26, p = 0.0003) and FVC (r(2) = 0.20, p = 0.002) were also associated with pVO(2). In multi-variable analysis independent determinants of pVO(2) were NT-proBNP (r(2) = 0.27, p = 0.001), FVC (r(2) = 0.20, p = 0.0002) and lean body weight (r(2) = 0.23, p = 0.001). NT-proBNP and FVC together were better predictors of pVO(2) < 60% (C statistic = 0.83, 95% CI 0.71, 0.95) than either NT-proBNP (C = 0.80, 95% CI 0.66, 0.94) or FVC (C =0.73, 95% CI 0.57, 0.89) alone. NT-proBNP, FVC and age also predicted excessive ventilation on cardio-pulmonary exercise (combined r(2) = 0.54, p < 0.0001).


CONCLUSIONS
In patients with mixed heart valve disease NT-proBNP and spirometry provide a more reliable assessment of functional capacity than assessment by echocardiography and symptoms alone.
Green Lane Cardiovascular Service, Auckland City Hospital, Auckland, New Zealand. naylinbissessor@hotmail.com
Naylin
N
Bissessor
Yong Shen
YS
Wee
Rohan
R
Jayasinghe
Irene
I
Zeng
Boris
B
Lowe
John
J
Kolbe
Kevin
K
Ellyet
Andrew
A
Kerr
Harvey
H
White
Ralph
R
Stewart
D004452:Echocardiography; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006349:Heart Valve Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D020097:Natriuretic Peptide, Brain / Q000378:metabolism*; D010101:Oxygen Consumption; D010446:Peptide Fragments / Q000378:metabolism*; D015203:Reproducibility of Results; D013147:Spirometry
D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain