Volume of infarcted area in acute myocardial infarction (AMI) can be detected by-

Ref : harrisons-manual-of-medicine-16th-edition pg no: 622 PHYSICAL EXAMINATION Pallor, diaphoresis, tachycardia, S4, dyskinetic cardiac impulse may be present. If CHF exists, rales and S3 are present. Jugular venous distention is common in right ventricular infarction. ECG ST elevation, followed by T-wave inversion, then Q-wave development over several hours (see Figs. 118-3 and 118-4. Non-Q-Wave MI (Also termed non-ST elevation MI, or NSTEMI) ST depression followed by persistent ST-T-wave changes without Q-wave development. Comparison with old ECG helpful CARDIAC BIOMARKERS Time course is diagnostically useful; creatine phosphokinase (CK) level rises within 4-8 h, peaks at 24 h, returns to normal by 48-72 h. CK-MB isoenzyme is more specific for MI but may also be elevated with myocarditis or after electrical cardioversion. Total CK (but not CK-MB) rises (two- to threefold) after IM injection, vigorous exercise, or other skeletal muscle trauma. A ratio of CK-MB mass:CK activity  2.5 suggests acute MI. CK-MB peaks earlier (about 8 h) following acute reperfusion therapy . Cardiac-specific troponin T and troponin I are highly specific for myocardial injury and are the preferred biochemical markers for diagnosis of acute MI. They remain elevated for 7-10 days. Serum cardiac markers should be measured at presentation, 6-9 h later, then at 12-24 h. NONINVASIVE IMAGING TECHNIQUES Useful when diagnosis of MI is not clear. Echocardiography detects infarct-associated regional wall motion abnormalities (but cannot distinguish acute MI from a previous myocardial scar). Echo is also useful in detecting RV infarction, LV aneurysm, and LV thrombus. Myocardial perfusion imaging (thallium 201 or technetium 99msestamibi) is sensitive for regions of decreased perfusion but is not specific for acute MI.