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  • Title: Chronotropic and neurohumoral markers for the evaluation of functional capacity in patients with impaired left ventricular function.
    Author: Kallistratos MS, Dritsas A, Laoutaris ID, Cokkinos DV.
    Journal: Hellenic J Cardiol; 2008; 49(1):26-32. PubMed ID: 18350779.
    Abstract:
    INTRODUCTION: Brain natriuretic peptide (BNP) levels correlate with functional capacity in patients with heart failure. Autonomic dysfunction and baro-chemo reflex balance play a role in conditioning exercise tolerance and chronotropic competence in heart failure. In this study we examined the relationship between N-terminal pro-brain natriuretic peptide (NT-pro-BNP) and heart rate (HR) response during cardiopulmonary exercise testing and the ability of those two markers to detect low functional class patients. METHODS: We studied 100 patients (age 59 +/- 13 yrs) with heart failure and left ventricular ejection fraction 35 +/- 9% who underwent treadmill cardiopulmonary exercise testing using the Dargie protocol. HR response was assessed by the chronotropic response index (CRI), which is calculated using the formula CRI = (peak HR - rest HR) /(220 - age - rest HR) x 100 (%). Blood samples for NT-pro-BNP assessment were taken before exercise. RESULTS: The overall peak VO2 achieved was 18 +/- 5 ml/kg/mm and CRI was 70 +/- 26% (normal value >80%). CRI correlated both with peak VO2 (r = 0.50, p < 0.001) and VE/VCO2 (r = -0.24, p < 0.05). Peak VO2 correlated strongly with NT-pro-BNP (r = -0.77, p < 0.001). NT-pro-BNP values >335 pg/ml showed 83% sensitivity and 76% specificity for detecting peak VO2 values <20 ml/kg/mm (AUC=86%, p < 0.001). CRI values >79% showed 70% sensitivity and 60% specificity for detecting peak VO2 values <20 ml/kg/mm (AUC=72%, p < 0.001). CRI correlated well with NT-pro-BNP at rest (r = -0.31, p < 0.001). CONCLUSIONS: In patients with heart failure, CR1 correlates significantly with both functional capacity derived from cardiopulmonary exercise testing and NT-pro-BNP levels. These findings may support the use of CR1 as a simple noninvasive marker of heart failure severity.
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