ECG is the most important tool in initial evaluation of myocardial infarct. The most specific and sensitive cardiac enzyme is troponin T and. 2D- echo gives more information on left and right ventricular functional status. Coronary angiography is the investigation of choice in the patients with myocardial infarction.

 

Blood test

• Complete blood count
• Cardiac enzymes
• Serum electrolytes
• Renal function test- blood urea and serum creatinine
• Lipid profile
• C-reactive protein

Cardiac enzymes

In patients with suspected heart attacks, obtain cardiac enzymes at regular intervals, starting upon admission and serially for as long as 24 hours.

Troponin T and I levels

• Troponins have greater specificity and sensitivity than creatine kinase levels
• They are useful both diagnostically and prognostically.
• Serum levels increase within 3-12 hours from the onset of chest pain, peak at 24-48 hours, and return to baseline over 5-14 days.

Creatine kinase levels

Creatine kinase comprises 3 isoenzymes, (CK-MM), which is found mainly in skeletal muscle; (CK-BB), predominantly found in the brain; and myocardial muscle creatine kinase (CK-MB), which is found mainly in the heart.

CK-MB levels increase within 3-12 hours of onset of chest pain, reach peak values within 24 hours, and return to baseline after 48-72 hours. Levels peak earlier (wash out) if reperfusion occurs.

Myoglobin levels

Myoglobin levels are highly sensitive but not specific, urine myoglobin levels rise within 1-4 hours from the onset of chest pain and fall within 24 hrs.

Serum electrolytes

Need to close monitoring serum potassium and magnesium levels

Renal function test

Creatinine level is also needed prior to initiating treatment with an angiotensin-converting enzyme (ACE) inhibitor.

Complete blood count (CBC)

• CBC counts if myocardial infarction is suspected to rule out anemia as a cause of decreased oxygen supply and prior to giving thrombolytics.
• Leukocytosis is common in the setting of acute myocardial infarction.
• A platelet count is necessary if platelet aggregation inhibitors are used.

Lipid level profile

• This is useful if obtained at the time of admission because levels can change after 12-24 hours of an acute illness.
• Increase in total cholesterol levels, LDL- cholesterol and triglycerides are at higher risk for thrombus formation
• Increase in HDL – cholesterol levels age good to heart and are cardioprotective

C- reactive protein

C- reactive protein levels are elevated in acute coronary syndrome

Imaging studies

Chest X-ray

• To asses heart size and the presence or absence of decompensated congestive heart failure with or without pulmonary edema.
• Also to diagnose pneumonia in elder individuals
• Helpful in evaluation if aortic dissection

2D- echo

• It plays an important role in diagnosis of heart attack
• An echocardiogram can also define the extent of the infarction and assess overall left ventricle (LV) and right ventricle (RV) function.
• Regional wall motion abnormalities can be identified.

Cardiac angiography

• Invasive and non invasive coronary angiography
• Cardiac angiography defines the patient's coronary anatomy and the extent of the disease.
• Patients with cardiogenic shock, intractable angina despite medications, should undergo cardiac catheterization immediately.

Other tests

ECG- echocardiogram

• ECG is the most important tool in the initial evaluation and triage of patients.
• It is confirmatory of the diagnosis in approximately 80% of cases.
• ST segment elevation (STMI) - elevation of ST segment and T wave inversion or tall/peaked T waves
• Non ST segment elevation (NSTMI)- ST depression and T wave inversion
• Obtain daily serial ECGs for the first 2-3 days and additionally as needed.