<P> There are a number of different biomarkers used to determine the presence of cardiac muscle damage . Troponins, measured through a blood test, are considered to be the best, and are preferred because they have greater sensitivity and specificity for measuring injury to the heart muscle than other tests . A rise in troponin occurs within 2--3 hours of injury to the heart muscle, and peaks within 1--2 days . The gross value of the troponin, as well as a change over time, are useful in measuring and diagnosing or excluding myocardial infarctions, and the diagnostic accuracy of troponin testing is improving over time . One high - sensitivity cardiac troponin is able to rule out a heart attack as long as the ECG is normal . </P> <P> Other tests, such as CK - MB or myoglobin, are discouraged . CK - MB is not as specific as troponins for acute myocardial injury, and may be elevated with past cardiac surgery, inflammation or electrical cardioversion; it rises within 4--8 hours and returns to normal within 2--3 days . Copeptin may be useful to rule out MI rapidly when used along with troponin . </P> <P> Electrocardiograms (ECGs) are a series of leads placed on a person's chest that measure electrical activity associated with contraction of heart muscle . The taking of an ECG is an important part in the workup of an AMI, and ECGs are often not just taken once, but may be repeated over minutes to hours, or in response to changes in signs or symptoms . </P> <P> ECG readouts product a waveform with different labelled features . In addition to a rise in biomarkers, a rise in the ST segment, changes in the shape or flipping of T waves, new Q waves, or a new left bundle branch block can be used to diagnose an AMI . In addition, ST elevation can be used to diagnose an ST segment myocardial infarction (STEMI). A rise must be new, in two adjacent adjacent ECG leads, greater than 2 mm (0.2 mV) for males and greater than 1.5 mm (0.15 mV) in females in all leads except for V2 and V3, where it must be greater than 1 mm (0.1 mV). ST elevation is associated with infarction, and may be preceded by changes indicating ischemia, such as ST depression or inversion of the T waves . Abnormalities can help localize the location of an infarct, based on the leads that are affected by changes . Early STEMIs may be preceded by peaked T waves . Other ECG abnormalities relating to complications of acute myocardial infarctions may also be evident, such as atrial or ventricular fibrillation . </P>

Myocardial infarction leads to impairment of ventricular function because