Study On The Effect Of Shenmai Injection On The Level Of Serum B-type Natriuretic Peptide In The Early Stage Of Acute Myocardial Infarction

B-type natriuretic peptide, a neuroendcrine hormone synthesized and secreted predominantly by ventricle, plays an important role in regulating the balance of blood pressure, body fluid and electrolyte. Recent studies have shown that the circulating level of BNP in the early stage of acute myocardial infarction has close relationship with ventricular remodeling and prognosis in patients with transmural myocardial infarction.In this experiment, we use enzyme-linked immunosorbent assay to study the dynamic changes of serum B-type natriuretic peptide levels in the early stage of acute myocardial infarction. We want to find out the effect of Shenmai injection on the level of BNP and the state of cardiac function. The value of Shenmai injection in ventricular remodeling and prognosis will be estimated indirectly to provide a reliable way to the therapy of AMI in the early stage. Objective: To observe the effect of Shenmai injection on the level of serum B-type natriuretic peptide and the cardiac function in the early stage of acute myocardial infarction.Method: We use ELISA to estimate the dynamic levels of serum BNP in 42 patients receiving reperfusion by thrombolysis treatment. All the AMI cases enrolled have been divided into two groups randomly, the routine treatment group and the Shenmai treatment group. Serums are taken at the in-hospital time, 3rd, 5th and 7th day in patients with AMI. The level of BNP and the cardiac function at different time will be compared between the two groups. The serum BNP level in healthy comparison group will be compared with that in patients with AMI.Result: The level of serum BNP is obviously higher in patients with AMI than that in healthy comparison group. The time course of BNP appears to have two peaks in both two groups of AMI, but there is no significant difference between them within the first 24 hours after admission. The level of serum BNP is significantly higher in the routine treatment group than that in the Shenmai treatment group 24 hours later. The cardiac function and left ventricular ejection fraction in the Shenmai treatment group are better than the routine treatment group.Discussion: Acute myocardial infarction, which means the necrosis of myocardium, is a kind of urgent and severe disease in the cardiovascular system. It is mainly caused by the decrease or completely loss of blood stream in the relevant coronary artery. It has more complications and higher mortality. With the development of our life, the average age of people in our country increases. The morbidity of coronary disease, especially acute myocardial infarction is rising; however, the mortality in the acute stage is decreasing because of the new therapies. Nevertheless, patients survive AMI often suffer cardiac dysfunction in the chronic stage. Myocardia have been elongated and get thinner in the infarcted area, while hypertrophy is found to compensate cardiac function in the noninfarcted area. All of these result in the dilatation of heart, the decrease of cardiac function, the occurrence of severe heart failure and even death in the late stage. Left ventricular remodeling, which has close relationship with long-term mortality, is one of the indices to evaluate the prognosis of AMI. Connections between BNP and AMI have been found recently, which suggest that BNP may be an index to judge ventricular remodeling and prognosis of myocardial infarction.B-type natriuretic peptide, which was first isolated from the porcine brain, is also called brain natriuretic peptide; however, it turned out to be more in heart than brain. Ventricular myocardium is the main place for BNP synthesis and release. The effects of BNP include natriuresis, vasodilation, inhibition of the sympathetic nervous system and rennin-angiotensin and aldosterone system, anti-mitogenic effects on myocardial cells and so on. Left ventricular stretch and increases in wall stress are mainly triggers for BNP release. Lated studies suggest that ischemia is another factor to increase the level of BNP. Since it is released rapidly when there is no irreversible tissue injury or significant change in diastolic volume, the level of BNP can reflect the degree of cardiac ischemia. Injury follows ischemia, so BNP increases earlier than traditional biomarkers. It may have great value in the diagnosis of acute coronary syndrome and estimating the range of ischemia.We can observe from the experiment that the level of BNP at in-hospital is markedly higher in patients with AMI than healthy comparison group (P<0.01). This result suggests that ischemia stimulates the synthesis and release of BNP. When admission BNP in all patients with AMI exceeds the normal range; 80.95% of them serum CK-MB exceed 25U/L, 23.81% exceed 50U/L; 88.10% of them Serum cTnI; exceed 0.04ng/ml, 50% exceed 0.5ng/ml. Pearson correlation assay, which is carried out between BNP and CK-MB, cTnI at admission and peak level, suggests that there is a positive correlation between them. The result is in accordance with foreign reports. It indicates that BNP has high sensibility in the diagnosis of AMI and may be an indirect index to reflect the infarct size having great value in estimating the range of ischemia. However just ischemia will cause the increase of BNP, the speciality in diagnosing AMI need further study.Latest studies demonstrate that there are correlations between BNP and congestive heart failure. It is a sensitive index of asymptomatic and diastolic cardiac dysfunction. BNP can predict the mortality of congestive heart failure. Significant association between BNP and cardiac function is obvious after 5 days, but not at admission. There is a positive correlation between BNP and Killip class and a negative correlation between BNP and left ventricular ejection fraction 5 days later. This result suggests that cardiac dysfunction when AMI onset is different from congestive heart failure. The level of BNP at in-hospital depends both on the increase of wall stress and the degree of ischemia. Successful reperfusion releases the ischemia, so the level of BNP mainly depends on the wall stress of ventricle which is similar to congestive heart failure.Many studies have proved that Shenmai can improve coronary circulation and protect the ischemia myocardia. Our study is based on the fact that BNP is synthesis and released by myocardia located in the infarcted and noninfarcted area. So it can reflect the state of ischemia and stretch of unnecrosis myocardia. Dynamic observations of BNP in the two groups demonstrate that there are two peaks in the early stage of AMI, the first one at 16 hours after admission while the second on the 5th day. The level of BNP on 3rd day is significantly higher than 5th day in the routine treatment group while there is not significant difference between them in the Shenmai group. The levels of BNP are significantly lower in the Shenmai group than in the routine treatment group on 3rd, 5th and 7th day. Since there is no significant difference between the two groups in infarct position, maximum level of CK-MB, cTnI and BNP, the result indicates that Shenmai injection can protect the ischemia myocardia as well as decreasing the level of serum BNP.Foreign and domestic studies demonstrate that BNP is a significant index to reflect ventricular remodeling, estimate the prognosis of patients with AMI. There is a close correlation between BNP and mortality, heart failure, and new myocardial infarction. We observe that Shenmai injection can reduce the level of BNP in the early stage of AMI in this research. It indicates that Shenmai injection may improve ventricular remodeling and prognosis of patients with AMI. But follow-up need to be carried out to prove it.Lots of oxygen-free radicals, which are generated during the reperfusion, cause myocardium stunning and cardiac dysfunction. This phenomenon can last hours, days and even weeks. Myocardium stunning is reversible, but the longer it lasts the slower it recovers. The advents of many complications such as heart failure, arrhythmia, ventricular remodeling etc happen in this time course. All of these may bring negative effect to the remedy of MI.Domestic studies on the treatment of reperfusion injury with Chinese traditional medicine suggest that many of them have effect on eliminating free radicals, preventing arrhythmia caused by reperfusion and accelerating the recovery of cardiac function. We also observe that there are significant differences in Killip class between the two groups. Left ventricular ejection fraction in Shenmai treatment group is higher than that in routine treatment group. Besides intensifying cardiac contract, the effect of anti-oxygen-free radicals, release from cardiac stunning may relate to cardiac state. But further studies are needed to prove it.Conclusion: Shenmai injection can decrease the level of serum BNP in the early stage of acute myocardial infarction and improve cardiac function.