The Clinical Research Of BNP Level In Serum For Early Diagnosis Of Patients With Acute Myocardial Infarction

PrefaceAMI is one of the most severe clinical type of CHD, often occurs in middle and old age ones. To develop and research new index that can diagnose AMI early has significant clinical meanings for further decreasing the bad cardiovascular events and improving patient's prognosis. BNP is one kind of peptide hormone. Recent research shows that there is a relationship between BNP and myocardial ischemic disease. In the patients with AMI the increase of plasma BNP level can predict the AMI patient's death incidence of short, mid and long term and nonfatal cardial events which can be used as the classical index of AMI. Some scholars think BNP can provide important diagnosis and prognosis information for suspicious on ensured AMI patients . But in recent years, whether can BNP should be used as a kind of specific or supplementary index for early diagnosis of AMI and guide clinical determination is a hot point in cardiovascular field. The aim of this research is to further discuss the dynamic changes in the patients with no cardiac insufficiency after the onset of AMI and also the clinical significance of the early diagnosis of AMI.Materials amd Methods1. Source And Group Of Cases :Choose 20 SA cases, 20 UA cases , 40 AMI cases due to chest pain from the Circulatory Department of Internal Medicine of Shenzhen Hospital, from January 2008 to January 2009 . The diagnosis standard meet the diagnosis and therapy guideline of ACS of ACC/AHA in 2000. 20 healthy physical examination cases as healthy comparting group.Exclusion Standard : aged more than 80 cases or less than 18 years , Heart Failure with symptoms , Left Ventricular EF less than 50 % , Renal insufficiency , Valvular Heart Disease , Cardiomyopathy , Supraventricular or Ventricular Tachycardia , COPD , Pulmonary Embolism and Unknown Onset Time.2. Methods1). The collection of samples :The patients in comparing group and SA group were drawed cubital vein blood in the morning , patients in the UA group were drawn blood within 24 hours after the last onset, patients in the AMI group were drawn blood in 2h , 4h , 6h , 24h after the onset time . Collect the blood serum and get it centrifuged within 24 hrs and keep it in refrigerator with the temperature -80℃. Assay the blood serum BNP concentration with ELISA within 1 week. Determine the serum CTnI concentration of AMI patients by withdrawing the venous blood after 6h of onset with chemical Luminiferous Immunological Method.2). Statistical treatment:Measurement data was expressed by means of x±s. SPSS 11.0 software was used for comparing, p <0.05 was significant. The relativity test between BNP and cTnI was used by double variable linear return analysis. Use ROC curve to gain the predicted value of BNP for AMI and the cut off; sensitivity; specificity, and evaluate the accuracy of the BNP according to AUcs.Result1. General data comparison between subjects in different group:There is no statistical difference in Age , Sex , Past Smoking History , Diabetic , Hyperglycemia in the 4 groups. 2. Dynamic change of Plasma BNP in different time points after AMIonset and comparison in groups.(1) BNP level is higher in SA group than in comparing group , but no statistical difference , p = 0.598 ; BNP level in UA group and each AMI time point is obviously higher than UA group , p<0.01 .(2) BNP level of each time point of AMI and BNP level in UA group are obviously higher than SA group ,p<0.01(3)BNP level in 2h after the onset of AMI is little higher than UA group , but it does not have any statistical difference , p = 0.961 ; BNP level in 4h , 6h , 24h after AMI onset are obviously higher than UA group , p<0.01(4)With the onset time prolonging , BNP level in AMI group is increasing obviously , the comparison among groups have obvious difference , p<0.013. The relativity between BNP level and cTnI in AMI group:Each two of the return analysis shows that the BNP level and cTnI are having positive relativity in 6h after the AMI onset, r=0.874 , p<0.014. ROC curve analysis about BNP level in different time points ofAMI patients:(1) 2h after AMI onset: surface area under ROC curve is 0.695 , p<0.01 ,cut off is 120 , sensitivity is 72.5% , specificity is 70 %.(2) 4h after AMI onset: Surface area under ROC curve is 0.821 , p<0.01 , cut off is 175 , sensitivity is 72.5% , specificity is 80%.(3) 6h after AMI onset: Surface area under ROC curve is 0.896 , p<0.01 , cut off is 210 , sensitivity is 77.5% , specificity is 90%.DiscussionThe serum BNP is mainly secreted by the left ventricle , it is secreted by proBNP. Latin and other researches has found that the concentration of plasma BNP in patients with AMI is obviously higher than that in patients with UA. And the plasma BNP has increased during the early period ( 6h ) of AP symptom onset in patients with CHD , the research proves that the ischemia may be the important promoting factor of BNP releasing . In this test , the serum BNP level of receivers abviously increases with the aggravation of myocardial ischemic degree , the plasma BNP level of the AMI group is the highest. The UA group is the second and SA group is the last but the concentration difference of BNP between SA group and comparing group has no statistic meaning (p>0.05) . This research proves that the plasma BNP level has obviously rise after the symptom onset for 2 hours , the plasma BNP level of 4h , 6h , 24 h has statistic comparison with the non-AMI group and within 24 h after the onset of AMI. With prolonged onset time, the degree of plasma BNP increases abviously.At present, cTnI and others are used as the main biochemistry index for the ACS patients . In clinical terms Risk factor classification is widely accepted by clinical doctors and examiner here in china and abroad. This research shows the change of BNP concentration and the cTnI level are correlated by the serum BNP and cTnI of 6h of AMI onset simultaneously which is meeting conclusion of recent year's research.So BNP level is hoped to be another new efficient cardiac biochemistry marker of prognosis of ACS patients after cTnI. BNP concentration can not only be used as evaluating index for AMI patient's cardiac function but can be used a accessory index for the AMI early diagnosis with troponin. The increased biochemical marker in blood after the onset of AMI is the marker of early diagnosis. This research has used ROC curve to make further quantitative analysis about the diagnosis ability of different onset time . We find that the BNP level of 4h after AMI onset has good diagnosis ability , the surface area under ROC curve is 0.821 . When the diagnostic cut off is 175, the sensitivity is 72.5% and specificity is 80% . And the BNP level of 6h after the onset of AMI has better diagnosis ability. The surface area under ROC curve is 0.896, when the diagnostic cut off is 210 , the sensitivity is 77.5% and the specificity is 90 %. Traditional evaluated index for the prognosis of AMI such as the coenzyme of CK-MB and cTnI are released by cardiac cells. But BNP is synthesized and secreted by integral even normal cardiac cells which can reflect the pathophysiological results. Thus, the measurements of serum BNP level can provide important supplementary information for evaluating myocardial ischemia or necrosis. Especially in the early period of ischemia and injury serum BNP are more important when cTnI and other markers are negative.Conclution1. The serum BNP level rise in 2h in patient with AMI and the longer the patient have the disease the BNP level is higher.2. After 6h from the onset of AMI the serum BNP level is positively correlated to the cTnI.3. After 4h , 6h from the onset of AMI the serum BNP level have good diagnostic value for AMI.