Myocardial Infarction
Signs and Symptoms
Chest pain, usually across the anterior precordium; described of tightness or squeezing
Pain may radiate to the arm, jaw, neck, arms, or back.  Usually affects the left side.
Dyspnea, which may either accompany chest pain or not
Nausea and/or abdominal pain (often present in infarcts of the inferior wall)
Anxiety, diaphoresis, lightheadedness, and/or syncope
Elevated creatinine kinase (CK-MB) enzymes
Chest pain and altered ECG readings
ST elevated initially, followed by T wave inversion with ST depression
Pathological Q-waves may appear within a couple hours or 24+ hours
Non-Q wave infarct: ST depression and T wave inversion may occur without ST elevation
Acute Treatment
Therapy Reason
Aspirin chewable 160-325mg stat decreases mortality 25% when used alone (40% when combined with other thrombolytic therapies)
Analgesia: morphine 2-5mg iv q5h prn relief of pain and anxiety associated with MI
Oxygen (> 90% saturation with 2-4L nasal cannula) general measure used in treatment of MI.  Improves overall mortality
Nitroglycerin 10mcg/min for 24-48 hours after first symptoms used to reduce ischemic events associated with myocardial infarction
Thrombolytics (streptokinase, alteplase) decreases morbidity and mortality about 30% (time dependent)
ACE inhibitors initiated within 24 hours decreases morbidity and mortality; greater benefit shown in patients with heart failure (EF < 40%) anterior wall myocardial infarction
Lopressor 5mg iv q15m x 3 doses, followed by oral medication 12 hours after last iv dose decreases incidence of ventricular arrhythmias, reinfarction, ischemia, and mortality
Heparin within first 24-48 hours (to aPTT 1.5-2.0 times control (50-70 seconds) shown to have beneficial effect on morbidity and mortalitiy; give after steptokinase/urokinase and give with alteplase/retaplase
Calcium channel blockers may be considered in non-Q wave myocardial infarction who have preserved LV function and no edema; also can be used to treat ischemia, hypertension, and atrial fibrillation if beta-blockers are contraindicated
Secondary Treatment
EC Aspirin 80-325 daily decreases rate of reinfarction and mortality by about 25%
ACE inhibitors (ramipril) decreases morbidity and mortality in patients with left systolic failure; continue for 4-6 weeks post-MI and discontinue if no evidence of left systolic failure
Beta-blockers decreases reinfarction and mortality about 25%
Warfarin (maintain INR 2-3) consider in patients with the following: chronic/paroxysmial atrial fibrillation, left ventricular thrombus, unable to take aspirin, extensive wall motion abnormalities, large anterior wall MI, or severe LV systolic dysfunction
Lipid lowering therapy HMG-CoA reductase inhibitors reduce mortality.  Gemfibrozil improves mortality in patients with HDL cholesterol; goal LDL < 100mg/dl
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