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Relation between N-terminal pro-brain natriuretic peptide values and invasively measured left ventricular hemodynamic indices.

BACKGROUND
Pro-brain natriuretic peptide (proBNP) is synthesized in the left ventricle. In response to transmural pressure, it is secreted into the circulation and consequently cleaved to yield the active hormone BNP and its N-terminal fragment (NT-proBNP). Determination of NT-proBNP is used as an aid in the diagnosis of left ventricular dysfunction.


METHODS
We analyzed NT-proBNP-levels before left-heart catheterization in 115 patients. At the end of the study, we compared the NT-proBNP values to the invasively measured hemodynamic indices (left ventricular ejection fraction, maximum change in pressure over time [dP/dt(max)] and left ventricular end-diastolic pressure) and the clinically observed New York Heart Association (NYHA) classifications.


RESULTS
A significant (P=0.008) increase of the NT-proBNP values was observed in cases of low ejection fraction (less than 41%). Furthermore, a significant (P=0.03) increase of the NT-proBNP values was measured in cases of heavily reduced dP/dt(max) (less than 1500 mmHg/s). The increase of NT-proBNP values in cases of high end-diastolic pressures was distinct but not significant. In the clinical observation (NYHA classification), a significant increase of NT-proBNP levels corresponded to increasing severity of heart failure. However, a large standard deviation was seen in all groups.


CONCLUSION
Concerning low ejection fractions, a high end-diastolic pressure and strong reduced dP/dt(max) in all cases an increase of pro-BNP-values was seen. However, the partly reported strong correlation of the BNP value to the left ventricular ejection fraction, dP/dt(max) and left ventricular end-diastolic pressure results was not found in the cases of middle and moderate heart failure, in contrast to the clinical observation. Regarding the large standard deviation, it may be possible to discriminate an unfavourable course of heart failure in an early stage.