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. AIM: 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). CONCLUSION: 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.

Complex valve disease: pre-surgical functional capacity evaluation using peak oxygen consumption.

BACKGROUND AND AIM OF THE STUDY: Complex heart valve disease constitutes both mixed and multiple valve pathologies that coexist in a single heart. The chronicity of complex valve disease results in a slow decline in functional capacity. Currently, very few data exist relating to chronic complex valve disease. The clinical assessment of exertional dyspnea (NYHA class) is central to the decision to operate and predict a prognosis. Dyspnea causes significant functional limitations. Peak oxygen consumption (peak VO2) is the 'gold standard' of objectively measuring functional aerobic capacity, and is an important predictor of prognosis. The onset of dyspnea is the most common indication for valve surgery. The study aim, in patients with complex valve disease, was to: (i) objectively assess functional aerobic capacity using peak VO2; and (ii) compare the differences between NYHA classes I and II in relation to body composition, echocardiographic severity, and functional capacity METHODS: A total of 45 patients with complex valve disease, who had been referred for the timing of surgery, was evaluated. The control group comprised 15 healthy subjects. All patients underwent a clinical assessment (to determine NYHA class), echocardiography and cardiopulmonary testing (peak VO2). RESULTS: Patients with complex valve disease achieved significantly lower peak VO2 values than controls (16 +/- 5.9 versus 31.4 +/- 5.9 ml/kg/min; p = 0.0001). The peak VO2 (percentage predicted) was significantly different between asymptomatic (NYHA class I) patients (70.9 +/- 20%) and symptomatic (NYHA class II) patients (55.1 +/- 21%; p = 0.003), with an overlap between classes. There was no significant difference in the echocardiographic severity of the valve lesions between NYHA classes. In a multivariable regression analysis, the peak VO2 and VEN/VCO2 slope were powerful predictors of poor outcome (Hazards ratio 2.15, 5.62; p <0.05). CONCLUSION: Patients with complex valve disease show significant functional capacity impairment, which may be difficult to detect from their clinical presentation. Consequently, peak VO2 measurements are required for the objective evaluation of functional capacity. The detection of a decline in peak VO2 will improve the timing of valve replacement and repair, and avoid adverse outcomes.

The role of natriuretic peptides in patients with chronic complex (mixed or multiple) heart valve disease.

N-terminal prohormone B-type natriuretic peptide (NT-proBNP) is an important biomarker of prognosis in heart failure and single valve disease. There are limited studies of complex valve disease. Patients with complex valve disease adopt a sedentary lifestyle, so symptoms may be difficult to detect. The authors aimed to determine whether NT-proBNP correlates with the severity of the valve lesion and underlying cardiac function and whether resting NT-proBNP predicts impaired peak VO(2) in patients with complex valve disease. Forty-five patients with complex moderate to severe stenosis or regurgitation of the heart valves underwent a clinical assessment, echocardiography, resting NT-proBNP assessment, and formal cardiopulmonary exercise testing. In a multivariate analysis, the log NT-proBNP (beta=-9.3, SE=1.9, P<.0001) and lean body weight (beta=0.59, SE=0.22, P=.01) were dominant independent predictors of peak VO(2). An NT-proBNP value of 84 pmol/L had 77% sensitivity and 70% specificity to predict impaired functional capacity, peak VO(2) <60% (predicted), area under the curve=0.80. Resting NT-proBNP was the best predictor of peak VO(2) in patients with complex valve disease, while symptoms and ejection fraction are a less reliable guide.