Title: Biochemical approach to diagnose myocardial infarction
Biography: Anil Batta
Biochemical approach to diagnose myocardial infarction
Diagnostic criteria for AMI have classically been based on the triad of history, ECG and measurement of cardiac enzymes. The choice of 'cardiac enzymes' has been dictated by the evolution of laboratory techniques, commencing with measurement of aspartate transaminase and progressing to measurement of creatine kinase (CK) and its MB isoenzyme (CK-MB). Measurement of CK-MB has been shown by both clinical studies and rigorous statistical analysis to represent the best test for the diagnosis of AMI. Development of immunoassays for the cardiac troponins, i.e. cardiac troponin T (cTnT) and cardiac troponin (cTnI), has enhanced diagnostic specificity. These measurements are completely specific for cardiac damage, allow quantization of the extent of infarction and are diagnostically superior to CK-MB measurement. The majority require risk stratification into high- and low-risk groups. It is here that cardiac troponins have a major role. The measurement of cTnT has been shown in a large number of studies to enable risk stratification of patients with unstable angina. The combination of cTnT, admission ECG and stress ECG can be used for a comprehensive risk stratification of patients with unstable angina. The combination of cTnT, admission ECG and stress ECG can be used for a comprehensive risk stratification which can be completed by 24 h from admission, as well as allowing a safe discharge policy from the ED. Measurements of cardiac troponins can also be used to predict prognosis in patients with other diagnostic categories. Patients with cardiac failure can be risk stratified according to cTnT status. cTnT status on admission allows subdivision into high- and low-risk groups in patients presenting with ST segment elevation. Certainly, cTnT measurement can be incorporated into a clinical decision-making strategy to assign patients to investigation and management pathways. There is evidence that cTnT may be useful to guide therapeutic options. Improvements in diagnostic accuracy can reduce inappropriate long-term drug therapy. Finally, use of point-of-care testing (POCT) means that biochemical testing can be précised. It is important to establish as soon as possible whether patients who present with chest pain are having an acute myocardial infarction (AMI). Ideally, sensitive and specific serum myocardial markers could provide the basis for early detection as well as determine the status of reperfusion following thrombolytic therapy. In the ED study, CK-MB, myoglobin, and cTnI were equally sensitive (100%) for the detection of AMI in patients who presented 7.4-14 h after onset of chest pain. However, cTnI was the most specific serum marker (specificity 91.9% compared to CK-MB 85.6 %,).. Within the reperfused group, the relative increase of cTnT was greater than CK-MB. These findings show the clinical utility of cardiac-specific troponins as markers for the early detection of AMI and monitoring of reperfusion following thrombolytic therapy. The cardiac troponins, in particular, have become the cardiac markers of choice for patients with ACS. Indeed, cardiac troponin is central to the definition of acute myocardial infarction (MI) in the consensus guidelines. These changes were instituted following the introduction of increasingly sensitive and precise troponin assays.Note that cardiac markers are not necessary for the diagnosis of patients who present with ischemic chest pain and diagnostic ECGs with ST-segment elevation. These patients may be candidates for thrombolytic therapy or primary angioplasty. Treatment should not be delayed to wait for cardiac marker results, especially since the sensitivity is low in the first 6 hours after symptom onset. The objective of this study was to compare the levels of troponins and enzymes levels in myocardial infarction and skeletal muscle injury. This study was carried out in GGS Medical College & Hospital, Faridkot, Punjab and India. Fifty subjects selected were cases suffering from myocardial infarction. Fifty patients were selected as control. These were the persons who were healthy & accompanying the patients. Creatine kinase, aspartate amino-transferase, lactate dehydrogenase and Troponin T were determined by kit methods. Troponin I level rises significantly (p<0.01) in patients suffering from myocardial infarction. Creatine kinase (CK), CKMB, aspartate aminotransferase and lactate dehydrogenase levels rises significantly (p<0.01) in disease group compared with controls. Troponin T is an early indicator of myocardial infarction and is superior to CKMB in diagnosis of myocardial injury. There is no increase in troponin T levels in skeletal muscle injury.