Acute Myocardial Infarction
Posted by Anil

Acute MI (2 out of 3 criteria)

1)30 minutes retrosternal pain - must R/O MI, PE, Aortic dissection

2)Cardiac enzymes elevated

3)ECG changes


Unstable Angina -Chest pain at rest - cardiac ischemia w/o ECG changes


MI Causes - Related to stenosis of coronary arteries

Thrombosis – must consider coagulopathy in post-acute phase

Cocaine (Present similar to infarction or ischemia – Benzodiazepam, Nitrates, ASA is 1st line – avoid Beta-blockers – unopposed alpha-agonst activity worsens vasospasm; try CCB & alpha-blockers)

              Dilated pupils (inhibits catecholamine – sympathetic activity) and blood-crusted nose


Vasospasm (Prinzmetal’s angina – CCB)

Coronary dissection

Aortic root dissection


Symptoms: Chest: Pressure, Dyspnea, Diaphoresis, Nausea/Vomitting;
Signs of Heart Failure 2o to MI: Pedal edema, CHF, Elevated JVP

70 yo diabetics or females – atypical MI presentations - Dyspnea, Pulmonary edema, Arrythmia

S3 - Severe systolic dysfunction – Dialated heart failure

S4 - Myocardiac noncompliance from ischemia - atrial contraction against stiff ventricle (V hypertrophy)


ECG Story of MI

Hyperacute T (Tall T is impending infarction – often hyperkalemia)

ST elevation

Q wave development + R wave shrinkage

ST back to normal (if stays persistently for a week - consider LV aneurysm)

T wave inversion

Normal T wave


STEMI - ST elevation 1mm in 2 contiguous leads or new LBBB

Anterior V2-4 LAD

Lateral I, aVL, V5, V6 LCX

Inferior II, III, aVF RCA

Septal aVR, V1, V2


Cardiac Enzymes

CK 4-8hr (normal in 48-72hrs)

Trop1 6hrs (normal in 7-10 days) - 6 hours apart

TropT 6hrs (normal in 10-14 days) - 6 hours apart


Treatment of MI – Acute Stabilization (MONAH – Chest pain protocol)

Morphine - pain

Oxygen – positive O2­ into lungs

Nitates - increases coronary blood flow, dilates venous system

ASA - antiplatelets

Heparin - anticoagulant



Acute treatment (Breaking the clot)

TNK in first 12 hours

PCI in first 4.5 hours