Myocardial infarction
Myocardial infarction
- Healing process
- Within 24 hours, leukocytes infiltrate the area of cell death
- Proteolytic enzymes of neutrophils and macrophages begin to remove necrotic tissue by fourth day → thin wall
- Necrotic zone identifiable by ECG changes
- Collagen matrix laid down
- 10 to 14 days after MI, scar tissue is still weak
- Heart muscle vulnerable to stress
- Monitor patient carefully as activity level increases
- By 6 weeks after MI, scar tissue has replaced necrotic tissue
- Area is said to be healed, but less compliant
- Ventricular remodeling
- Normal myocardium will hypertrophy and dilate in an attempt to compensate for infarcted muscle
- Complications of myocardial infarction
- Dysrhythmias
- Most common complication
- Present in 80% to 90% of MI patients
- Can be caused by ischemia, electrolyte imbalances, or SNS stimulation
- VT and VF are most common cause of death in prehospitalization period
- Heart failure
- Occurs when pumping power of heart has diminished
- Left-sided HF
- Mild dyspnea, restlessness, agitation, slight tachycardia initially
- Right-sided HF
- Jugular venous distention, hepatic congestion, lower extremity edema
- Cardiogenic shock
- Occurs because of
- Severe LV failure, papillary muscle rupture, ventricular septal rupture, LV free wall rupture, right ventricular infarction
- Requires aggressive management
- Associated with a high death rate
- Papillary muscle dysfunction or rupture
- Causes mitral valve regurgitation
- Aggravates an already compromised LV → rapid clinical deterioration
- Left ventricular aneurysm
- Myocardial wall becomes thinned and bulges out during contraction
- Leads to HF, dysrhythmias, and angina
- Ventricular septal wall rupture and left ventricular free wall rupture
- New, loud systolic murmur
- HF and cardiogenic shock
- Emergency repair
- Rare condition associated with high death rate
- Acute pericarditis
- Inflammation of visceral and/or parietal pericardium
- Mild to severe chest pain
- Increases with inspiration, coughing, movement of upper body
- Relieved by sitting in forward position
- Pericardial friction rub
- ECG changes
- Dressler syndrome
- Pericarditis and fever that develops 1 to 8 weeks after MI
- Chest pain, fever, malaise, pericardial friction rub, arthralgia
- High dose aspirin is treatment of choice