Relationship of resting B-type natriuretic peptide level to cardiac work and total physical work capacity in heart failure patients.

PURPOSE: Plasma B-type natriuretic peptide (BNP) levels obtained at rest have been previously shown to be correlated with the global functional capacity measures of peak oxygen uptake (V(O(2peak))) and the minute ventilation/carbon dioxide (VE/V(O(2))) slope. The purpose of this study was to assess the relationship of the plasma BNP level to the rate-pressure product (RPP) as an indicator of central or cardiac work capacity.
METHODS: Twenty-two subjects (12 men), mean age 57 +/- 12 years, diagnosed with heart failure (8 ischemic/14 nonischemic) were recruited. All subjects were stable on optimal medical therapy for at least 1 month. Blood samples for BNP level analysis were obtained at rest. Subjects underwent a symptom-limited treadmill exercise test using a ramping protocol while V(O(2)), heart rate (HR), and blood pressure (BP) were monitored. Correlation analyses were conducted to assess the relationship of BNP level to RPP level, V(O(2peak), VE/V(O(2)) slope, end-tidal CO(2) pressure (P(ET)CO(2)), and left ventricular ejection fraction (LVEF).
RESULTS: Resting BNP levels were significantly correlated with RPP levels (r = -0.69). The BNP level and the RPP level were correlated with V(O(2peak)) (r = -0.63 and r = 0.66, respectively) and VE/V(O(2)) slope (r = 0.53 and r = -0.54, respectively). The RPP level but not the BNP level was correlated with P(ET)CO(2) (r = 0.57). Neither BNP nor RPP levels were well correlated with LVEF (r = -0.26 and r = 0.14, respectively). DISCUSSION: The results of this study suggest that resting plasma BNP level may be a useful clinical measure for evaluating both global functional capacity and myocardial specific work capacity in individuals with heart failure.

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