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Define myocardial infarction
A medical emergency in which some of the heart's blood supply is suddenly and severely reduced or cut off, causing myocardium to die because of deprevation of O2 supply.
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Etiology of myocardial infarction
- acute thrombus from plaque rupture occluding the artery
- arterial embolization rare
- coronary artery spasm from drugs
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What area of the heart is affected?
- The left ventrical but damage could extend to right ventricle or atria.
- In pts. that die, LV less than or equal to 50% mass damage
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Anterior Infarcts
- Larger
- Worse prognosis than inferior-posterior infarts
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Transmural Infarcts
Involve the whole thickness of mycoardium
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Signs and Symptoms of Myocardial Infarction
- 2/3 pts. symptoms days to weeks before MI
- Increasing angina-SOB-Fatigue
- 1st symptom: deep, substernal, visceral pain. radiates to jaw, back and arm. Isn't cured with rest or nitroglycerin
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What's the % of acute MIs that are silent or unrcognized?
20% because it's a mild chest discomfort
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Signs of Myocardial Infarction
- anxious
- sense of impending doom
- nausea/vomiting
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Other signs of Myocardial Infarction
- Severe pain
- restless and apprehensive
- pale, cool, diaphoretic skin
- peripheral or central cyanosis
- thready pulse
- variable BP
- distant heart sounds
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Complications of Myocardial Infartion
- *Arrhythmia: in less than 90%. Bradycardia.
- *Sinus node disturbaces: brady- no biggy unless above 50. tach- bad
- *Atrial arrhythmia: in 10%
- *AV block: Mobitz II-bad
- *Ventricular arrhythmias: common. Primary VFib1st few hrs.
- *Heart Failure
- *RV infarction
- *Hypoxemia: abNL V/Q matching, edema, atelectasis, shunting
- *Hypotenstion: decrease ventricular filling
- *Cardiogenic shock: mortality less or equal to 65%
- *Recurring ischemia: pericarditis or pulmonary embolus
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Diagnosis and Lab Finding of Myocardial Infarction
- Diagnosed by history
- Confirmed by ECG
- Supported by serial cardiac enzyme changes
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Blood Tests of Myocardial Infarction
- *Creatine Kinase: rises in 4-8 hr, peaks in 24 hrs, and is NL in 3-4 days
- *Troponin T & I: not in healthy, cardiac injury. Rises 4-6 hr, peaks 12-48 hr, elevated for 10 days.
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Prognosis of Myocardial Infarction
- of those who die, 60% die of primary VFib before reaching the hospital
- surviving the initial hospitalization, mortality 8-10%
- death in first 3-4 months
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Treatment GOALS of Myocardial Infarction
- Relieve distress
- Reverse ischemia
- Limit infarct size
- Reduce cardiac work
- Prevent/treat complications
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Treatment of Myocardial Infarction
- Quiet, calm, resful room in CCU
- Mild tranquilizer
- Don't smoke
- Diet-low Na, cholesterol and sat fats
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Initial Treatment of Myocardial Infarction
- Don't deny symptoms
- Rapid dx, alleviate & stabilize with thrombolytic
- Establish I.V. & draw blood for enzymes, do ECG
- Give aspirin
- Oxygen
- Morphine IV PRN
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Thrombolytic Therapy of Myocardial Infarction
- Most effective
- Greatest risk is hemmorrage
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Drugs to Reduce Cardiac Work in Myocardial Infarction
- B-Blockers
- ACE inhibitors
- Vasodilators
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Rehab for Myocardial Infarction
- Bed rest 1-3 days
- Chair rest, passive exercises
- NL activity after 6 weeks
- Regular exercise
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