Brain Natriuretic Peptide Changes After Acute Myocardial Infarction

Objective:1.To investigate brain natriuretic peptide (BNP) expression in left ventricular myocardium of Sprague-Dawlay rats with acute myocardial infarction (AMI).2.To explore the changes of blood brain natriuretic peptide levels in patients with acute myocardial infarction.Methods:1.Myocardial infarction model was successfully established by ligation of anterior descending coronary artery. Rats were randomized to five AMI groups (1 day, 3 days, 7 day, 14 days, 28 days) and one Sham-operated group.2.Semi-quantitative RT-PCR was used to examine BNP mRNA levels in left ventricular myocardium of rats with AMI.3.Western blot was applied to examine BNP protein levels in left ventricular myocardium of rats with AMI.4. 68 patients with AMI were followed up and analyzed. Blood BNP levels were measured on admission and at 1 day, 3 days and 7 days after admission. The follow-up period was 1 year.Results:1.Compared with the Sham-operated group, the mRNA levels of BNP in AMI groups were significantly increased at 1 day (0.913±0.036 vs 0.757±0.034, P<0.05), peaked at 3 days (0.971±0.027), then decreased, however, it remained higher than that in Sham-operated group even in 28 days (0.902±0.072 vs 0.757±0.034, P<0.05). 2.Compared with the Sham-operated group, the protein levels of BNP in AMI groups were significantly increased at 1 day (0.882±0.027 vs 0.565±0.086, P<0.05), peaked at 3 days (0.976±0.016), then decreased, however, it remained higher than that in Sham-operated group even in 28 days (0.873±0.033 vs 0.565±0.086, P<0.05).3.The blood levels of BNP on admission and at 1 day, 3 days, 7 days after admission , were 135.1±184.5 pg/ml, 397.4±388.2 pg/ml, 429.1±302.7 pg/ml, 525.6±507.3 pg/ml respctively, and increased gradually. The levels after admssion were significantly higher than that on admission (P<0.05), but there were no significant differences of the levels at 1 day, 3 days, 7 days after admission (P>0.05).4. BNP levels were higher on admission in patients who died compared with survivors (355.5±402.2 pg/ml vs 121.5±144.9 pg/ml), but there was no statistical significance (P>0.05). BNP levels at 1 day, 7 days after admission were significantly higher in patients who died compared with survivors (987.4±594.8 pg/ml vs 301.1±251.5 pg/ml, 1304.4±771.6 pg/ml vs 428.2±365.9 pg/ml, respectively, P<0.05).Conclusion:1.The BNP expression in ventricular myocardium of rats is increased after AMI, and presents dynamic changes, and peaked at 3 days after AMI. This may provides theoretical foundation for an optimal timing for BNP measurement, and is beneficial for BNP to provide prognositc value for AMI patients.2. The blood level of BNP after admission is gradually increased, but there are no obvious dynamic changes.3. The blood BNP level can be used as an predictor of cardiac death in patients with AMI.