EKG learning Myocardial infarction part 1
Myocardial infarction (MI) or acute myocardial infarction (AMI), commonly known as a heart attack, occurs when blood flow stops to a part of the heart causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Often it is in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat, or feeling tired.
Most MIs occur due to coronary artery disease. Risk factors include high blood pressure, smoking, diabetes, lack of exercise, obesity, high blood cholesterol, poor diet, and excessive alcohol intake, among others. The mechanism of an MI often involves the complete blockage of a coronary artery caused by a rupture of an atherosclerotic plaque. MIs are less commonly caused by coronary artery spasms, which may be due to cocaine, significant emotional stress, and extreme cold, among others. A number of tests are useful to help with diagnosis, including electrocardiograms (ECGs), blood tests, and coronary angiography. An ECG may confirm an ST elevation MI if ST elevation is present. Commonly used blood tests include troponin and less often creatine kinase MB.
causes include tobacco smoking,DM,high BP,dyslipidemia,obesity,genetics,OCP,family history etc.
A cardiac troponin rise accompanied by either typical symptoms, pathological Q waves, ST elevation or depression, or coronary intervention is diagnostic of MI.
WHO criteria formulated in 1979 have classically been used to diagnose MI; a patient is diagnosed with MI if two (probable) or three (definite) of the following criteria are satisfied:
Clinical history of ischemic-type chest pain lasting for more than 20 minutes
Changes in serial ECG tracings
Rise and fall of serum cardiac biomarkers
At autopsy, a pathologist can diagnose an MI based on anatomopathological findings.
For a person to qualify as having a STEMI, in addition to reported angina, the ECG must show new ST elevation in two or more adjacent ECG leads. This must be greater than 2 mm (0.2 mV) for males and greater than 1.5 mm (0.15 mV) in females if in leads V2 and V3 or greater than 1 mm (0.1 mV) if it is in other ECG leads. A left bundle branch block that is believed to be new used to be considered the same as ST elevation; however, this is no longer the case. In early STEMIs there may just be peaked T waves with ST elevation developing later.
While there are a number of different biomarkers, troponins are considered to be the best and reliance on older tests (such as CK-MB) or myoglobin is discouraged. This is not the case in the setting of peri-procedural MI where use of troponin and CK-MB assays are considered useful. Copeptin may be useful to rule out MI rapidly when used along with troponin.
A chest radiograph and routine blood tests may indicate complications or precipitating causes, and are often performed upon arrival to an emergency department.