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Keywords

BNP, functional capacity, myocardial work

 

Authors

  1. Norman, Joseph F. PhD, PT
  2. Pozehl, Bunny J. PhD, APRN
  3. Duncan, Kathleen A. PhD, RN
  4. Hertzog, Melody A. PhD
  5. Elokda, Ahmed S. PhD, PT
  6. Krueger, Steven K. MD

Abstract

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 ([latin capital V with dot above]O2peak) and the minute ventilation/carbon dioxide (VE/[latin capital V with dot above]CO2) 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 [latin capital V with dot above]O2, heart rate (HR), and blood pressure (BP) were monitored. Correlation analyses were conducted to assess the relationship of BNP level to RPP level, [latin capital V with dot above]O2peak, VE/[latin capital V with dot above]CO2 slope, end-tidal CO2 pressure (PETCO2), 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 [latin capital V with dot above]O2peak (r = -0.63 and r = 0.66, respectively) and VE/[latin capital V with dot above]CO2 slope (r = 0.53 and r = -0.54, respectively). The RPP level but not the BNP level was correlated with PETCO2 (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.