Abstract
BackgroundB-type natriuretic peptide (BNP) is increased in post-cardiac surgery patients, however the mechanisms underlying BNP release are still unclear. In the current study, we aimed to assess the relationship between postoperative BNP levels and left ventricular filling pressures in post-cardiac surgery patients.MethodsWe prospectively enrolled 134 consecutive patients referred to our Center 8 ± 5 days after cardiac surgery. BNP was sampled at hospital admission and related to the following echocardiographic parameters: left ventricular (LV) diastolic volume (DV), LV systolic volume (SV), LV ejection fraction (EF), LV mass, relative wall thickness (RWT), indexed left atrial volume (iLAV), mitral inflow E/A ratio, mitral E wave deceleration time (DT), ratio of the transmitral E wave to the Doppler tissue early mitral annulus velocity (E/E').ResultsA total of 124 patients had both BNP and echocardiographic data. The BNP values were significantly elevated (mean 353 ± 356 pg/ml), with normal value in only 17 patients (13.7%). Mean LVEF was 59 ± 10% (LVEF ≥50% in 108 pts). There was no relationship between BNP and LVEF (p = 0.11), LVDV (p = 0.88), LVSV (p = 0.50), E/A (p = 0.77), DT (p = 0.33) or RWT (p = 0.50). In contrast, BNP was directly related to E/E' (p < 0.001), LV mass (p = 0.006) and iLAV (p = 0.026). At multivariable regression analysis, age and E/E' were the only independent predictors of BNP levels.ConclusionIn post-cardiac surgery patients with overall preserved LV systolic function, the significant increase in BNP levels is related to E/E', an echocardiographic parameter of elevated LV filling pressures which indicates left atrial pressure as a major determinant in BNP release in this clinical setting.
Highlights
B-type natriuretic peptide (BNP) is increased in post-cardiac surgery patients, the mechanisms underlying BNP release are still unclear
B-type natriuretic peptide (BNP), a cardiac hormone synthesized by ventricular myocytes in response to left ventricular (LV) dysfunction and wall stress, has been shown to be increased in patients with cardiovascular disease such as heart failure,[1] cardiac hypertrophy,[2] and acute coronary syndromes [3]
In most of these situations the increase in BNP is related to systolic LV dysfunction [4], recent evidences suggest that, at least in patients with heart failure, elevated LV filling pressures may act as a trigger for BNP release [5,6] and are likely to reduce exercise capacity [7]
Summary
B-type natriuretic peptide (BNP) is increased in post-cardiac surgery patients, the mechanisms underlying BNP release are still unclear. It is worth noting that in post-cardiac surgery patients, as compared to patients with heart failure, LV ejection fraction does not correlate as much as expected with BNP levels [9] In this clinical setting, factors other than LV systolic function, such as myocardial damage during aortic cross clamping, have been advocated;[10] the results of these studies are still controversial and the mechanisms underlying BNP release remain unclear. We designed this prospective study with the aims of assessing the relationship between postoperative BNP levels and LV filling pressures as evaluated by transthoracic two-dimensional and Doppler echocardiography
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