BNP after Cardiac Surgery in Patients with Normal Ventricular Function
Authors: Venturini Elio , Leoni Antonella , Marabotti Claudio , Scalzini Alessandro , Testa Roberto 
Published: May 2017

Background: Brain natriuretic peptide (BNP) is proven marker for diagnosis and stratification of patients (P) with heart failure; furthermore it can be useful for differential diagnosis of dyspnea, for detection of diastolic dysfunction and as guide and monitoring of therapy. Acute coronary syndrome, atrial fibrillation (AF), aortic stenosis and hypertrophic cardiomyopathy are other conditions in which the BNP can be raised. Little is know about the level of BNP in P undergone cardiac surgery. Aim of the study was to detect the concentration of BNP immediately after CABG and to follow the course during cardiac rehabilitation (CR).

Methods: we studied 18 P (mean age 67.8±11.2 yrs) 9.1±3.6 days after surgery and we repeated the evaluation after our program of CR, in average 56 days of distance from CABG. In each P was performed an echocardiogram (inclusive study of right ventricle, diastolic function and DTI), a determination of BNP (NT-proBNP) and also the six-minute walking test (SMWT). Every effort was made for not varying the therapy during the period of observation. Exclusion criteria were: MI in the last 3 months, heart and renal failure, use of inotropics drugs and AF after cardiac surgery.

Results: the concentration of BNP was high in both determinations even if it lowered in the second (BNP1 vsBNP2: pg/ml 1225.1±873.2 vs 708.7±741 P < 0.001); also the left atrial volume decreased ( ml 50.7±11.6 vs 46.4±8.8 P < 0.01) while the ejection fraction didn't vary, (EF1 vs EF2: 57.2±6.7 vs 59.8±9.1 ns). There was an increase of the distance crossed to the SMWT ( mt 254.7±65.4 vs 435.3±69.6 P < 0.001); glycaemia and creatinine values were normal in both determinations while the hemoglobin increased (11.5±1.2 vs 13.2±1.3 P < 0.01). Other echo parameters(E/A, E/Em, TAPSE, PAPs ) were not meaningfully varied with the exception of DT (221.6±66.3 vs 253.8±72.3 P < 0.05). We have not found correlations between Ä BNP and: Ä LAV, Ä SMWT, Ä E/A or Ä E/Em. Instead, the relationship was statistically significant with the DT (r: 0.78 P < 0.01). Also the second determination of the BNP had the followings relationships:

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Conclusion: after CABG, the level of BNP is elevated also in P with normal ventricular function; the most elevated values were in the immediate proximity of surgery for then being reduced during CR program. The improvement of the diastolic function, pointed out by the increase of the DT, it seems to correlate with the reduction of natriuretic peptides; the relationship of the other indexes of diastolic function, of the EF and of the PAPs with the BNP is detectable only at the second collecting. Is possible to infer that conditions in narrow relationship with the surgery (extracorporeal circulation, quick variations of circulating volume, direct stimulation of the myocardium and impaired lung function due to sternotomy) can induce the liberation of the BNP; this can conceal the association between the incretion of BNP and the indexes of ventricular function.