What are the causes of postoperative ST-Elevation Myocardial Infarction (STEMI)?

Causes of Postoperative ST-Elevation Myocardial Infarction (STEMI)

Postoperative STEMI is most commonly caused by supply-demand mismatch (type 2 MI), though acute plaque rupture (type 1 MI) can also occur after noncardiac surgery. 1

Primary Mechanisms of Postoperative STEMI

Type 1 MI (Plaque Rupture)

• Acute thrombotic occlusion developing from an atherosclerotic plaque in an epicardial coronary vessel 2
• More common in patients with pre-existing coronary artery disease and hypertension 3
• Can occur due to perioperative stress triggering plaque instability and rupture 1

Type 2 MI (Supply-Demand Mismatch)

• Most common mechanism in the perioperative setting 1
• Caused by imbalance between myocardial oxygen supply and demand 1, 3
• Contributing factors include:
  • Hypotension
  • Tachycardia
  • Anemia
  • Hypoxia
  • Respiratory imbalances 3

Specific Mechanical Complications

Graft-Related Complications (Post-CABG)

• SVG (saphenous vein graft) thrombosis or occlusion 1
• Technical complications during early postoperative period 1
• Spasm in grafts or native vessels 1
• Intimal hyperplasia or atherosclerosis in SVGs (particularly thrombotic lesions) 1

Structural Complications

• Ventricular septal rupture (usually within first 24 hours) 1
• Left ventricular free-wall rupture (especially in first MI, anterior infarction, elderly, women) 1
• Mitral regurgitation due to papillary muscle rupture or LV remodeling 1
• Left ventricular aneurysm formation (more frequent with anterior infarction) 1

Patient-Related Risk Factors

• Advanced age 4, 3
• Female sex 4
• Low body weight 4
• Renal insufficiency 4
• Anemia 4, 3
• Pre-existing peripheral arterial disease 4
• History of previous MI or heart failure 3
• Hypertension during acute phase 1
• Lack of antecedent angina or prior MI 1
• Absence of collateral blood flow 1

Procedure-Related Risk Factors

• High-risk surgical procedures (vascular, prolonged operations) 1, 5
• Use of glycoprotein IIb/IIIa inhibitors 4
• Femoral access site complications in cardiac procedures 4
• Inadequate perioperative beta-blockade in high-risk patients 1
• Administration of fibrinolytic therapy >14 hours after symptom onset 1
• Use of corticosteroids or nonsteroidal anti-inflammatory drugs 1

Recognition Challenges

• Diagnosis of perioperative MI may be difficult due to:
  • Sedation and analgesia limiting patient's symptoms 1
  • Reduced ability to report symptoms 1
  • Atypical presentation in postoperative setting 6
  • Absence of typical chest pain 1

Management Considerations

• Patients who develop STEMI after noncardiac surgery should receive guideline-directed medical therapy (GDMT) and be considered for invasive coronary angiography (ICA) 1
• Treatment decisions must balance bleeding and thrombotic risks with the severity of clinical presentation 1
• For symptomatic perioperative STEMI, angioplasty should be considered when benefits outweigh risks 1
• Aspirin therapy should be started as soon as possible if not contraindicated 1
• Beta-blockers and ACE inhibitors may be beneficial for both symptom relief and long-term risk reduction 1

Prevention Strategies

• Preoperative optimization including appropriate revascularization when indicated 5
• Careful perioperative management of antiplatelet and anticoagulant medications 4
• Maintenance of hemodynamic stability 3
• Avoidance of significant anemia and hypoxia 3
• Appropriate pain management to reduce cardiovascular stress 3
• Glucose control (maintaining levels below 180 mg/dL while avoiding hypoglycemia) 4