Brain natiruretic peptide (BNP) is released from human left ventricle under conditions of volume and/or pressure overload and has been recently a focus of increasing interest since Agawa et al in 2000 demonstrated significant rise of serum levels of BNP in patients (pts) with heart failure (HF) due to variable etiologies. Itscompensatory role – in terms of enhancing natiuresis and lowering systemic vascular resistance – has been further confirmed by the recently shown quantitative correlation with the severity of cardiac dysfunction (both systolic and diastolic).The present study is intended to assess the possible diagnostic role that could be played by BNP in masking latent cardiac involvement in non cardiac critically ill pts with a potential for cardiac affection, which would influence the natural coarse andultimate outcome. To achieve this goal, we studied 80 critically ill pts (46 M, 34 F, mean age: 45 ys) divided into four groups: 20 pts each. Group I; cardiac pts with clinical evidence of HF, group II of compensated heart disease (5 ischemic, 5 rheumatic and 10 dilatedcardiomyopathy, group III; non cardiac critically ill pts of various etiologies, (systemic sepsis, CVA, ARDS, extra), 9 of them were on assisted mechanical ventilation and group IV of 20 healthy control subjects all groups were matched for age and sex.Following clinical evaluation, 12 leads ECG, echocardiography (M-mode 2D) and chest x-ray were done on admission, before discharge and at time of crises. Venous samples were drawn from all pts and control within 24 hours of admission, prior to discharge and at times of crises. Echocardiographic parameters assessedincluded LVEDD, LVESD, ejection fraction, fractional shortening and E/A ratio. On admission, pts with HF as well as those with compensated heart disease exhibited significantly higher levels of BNP than control subjects (8.4 ng/ml in HF pts, 2.3 ng/ml in compensated HD vs. 0.9 ng/ml in control subjects).The extent of rise of BNP correlates negatively with EF with r= 0.8.Of the 20 non cardiac critically ill pts studied, BNP was normal in 9 pts and abnormally elevated in 11 pts. Assessment by ECHO showed that compared to BNPnormal pts, those with abnormally elevated BNP had significantly lower ejection fraction (28% vs. 51%) and lower fractional shortening (15% vs. 34%). Out of the 11pts with abnormally high BNP, 9 (81%) died while only 3 (33%) died in those with normal BNP.IN CONCLUSION: Brain natriuretic peptide which has been previously recognized as a diagnostic and prognostic marker of heart failure, can also serve the important role of unmasking latent systolic and diastolic cardiac dysfunction in critically ill ptsadmitted for non cardiac problems. Our data point to the positive correlation with the severity of HF in previously cardiac as well as the extent of cardiac dysfunction in critically ill non cardiac pts.