Definition
Irreversible ischemic necrosis (death) of heart muscle due to complete blockage of a coronary artery.
Etiology & Pathogenesis
- Underlying mechanism: Rupture of an atherosclerotic plaque → thrombus → complete arterial occlusion.
- Less common causes: Coronary spasm (e.g. cocaine, extreme stress, cold), severe inflammation, embolism.
- Cascade: Arterial blockage → myocardial ischemia → ↓ contractility → ↓ stroke volume, HR, CO → acute heart failure and possible death.
- Timeline: >20–40 minutes of ischemia causes irreversible myocyte damage.
Symptoms
- Chest pain: retrosternal tightness or crushing pain, may radiate to left arm (especially last two fingers), jaw, back, epigastrium; lasts >30 minutes; does not change with position.
- Autonomic: sweating, nausea, vomiting, fatigue, syncope.
- Dyspnea (shortness of breath).
- Heart rate: usually tachycardia, except in septal infarction (AV-node involvement → AV block → bradycardia).
- Atypical presentations in women, elderly, diabetics, postoperative or critically ill: palpitations, vague discomfort, silent MI.
Physical Examination
- Skin: cold, clammy, pale.
- Vital signs: BP may be high (pain, catecholamines) or low (pump failure); HR typically elevated and may be irregular.
- Lung auscultation: crackles or non-resonant rhonchi if left-sided failure/pulmonary edema.
- Heart auscultation: possible premature beats; S3 gallop or systolic murmur at apex (due to acute mitral regurgitation from papillary muscle dysfunction).
- In chronic ischemic cardiomyopathy: arrhythmias and signs of left heart failure or hypertension.