What is the management of intraoperative myocardial infarction (MI) in patients undergoing non-cardiac surgery?

Intraoperative Management of Myocardial Infarction in Non-Cardiac Surgery

When MI occurs intraoperatively during non-cardiac surgery, immediately initiate aspirin, beta-blockers, and intravenous anticoagulation, then rapidly determine if this represents acute coronary occlusion (Type 1 MI) requiring emergency catheterization versus supply-demand mismatch (Type 2 MI) requiring hemodynamic optimization. 1, 2

Immediate Recognition and Diagnosis

• Obtain troponin measurement immediately in patients with ECG changes or chest pain typical of acute coronary syndrome, as troponin elevation with appropriate clinical context is more diagnostic than isolated ECG changes 1, 3
• Perform continuous cardiac monitoring and serial ECGs to track evolving changes and detect ST-segment elevation or new Q waves 1
• Obtain urgent echocardiography to assess ventricular function and detect mechanical complications such as ventricular septal defect or acute mitral regurgitation 1

Critical Decision Point: Identify the MI Mechanism

The management strategy hinges entirely on distinguishing between Type 1 MI (acute plaque rupture with thrombotic occlusion) versus Type 2 MI (supply-demand mismatch). 2, 3

Type 1 MI (Acute Coronary Occlusion):

• Presents with ST-segment elevation, new Q waves, or regional wall motion abnormalities on echocardiography 1
• Requires consideration for emergency cardiac catheterization and PCI if feasible within 12 hours of symptom onset 4, 1, 3
• Time to reperfusion is critical—any delay beyond 12 hours substantially reduces benefit 4

Type 2 MI (Supply-Demand Mismatch):

• More common in the perioperative setting, caused by tachycardia, hypertension, hypotension, anemia, or hypoxemia 2, 3
• Lowering heart rate and optimizing blood pressure is of greater benefit and carries less risk than emergency catheterization 4
• Focus on correcting the underlying cause rather than invasive intervention 2

Immediate Medical Therapy (Initiate Simultaneously)

All patients with intraoperative MI should receive standard medical therapy regardless of whether invasive management is pursued. 2

• Aspirin: Initiate immediately (loading dose) and continue indefinitely unless bleeding risk is prohibitive 4, 1, 2
• Beta-blockers: Start immediately to reduce myocardial oxygen demand through heart rate and blood pressure control, targeting heart rate 60-70 bpm and systolic BP >100 mmHg 4, 1, 2
• Intravenous anticoagulation: Initiate heparin to prevent further thrombosis 1
• ACE inhibitors: Especially beneficial in patients with low ejection fractions or anterior infarctions 4, 1, 2
• Nitrates: For ongoing chest pain and to reduce preload 1

Revascularization Decision Algorithm

For ST-Elevation MI or Hemodynamic Instability:

• Hemodynamically stable patients: Perform coronary angiography and PCI within 60 minutes from onset of symptoms if bleeding risk permits 1, 2
• Hemodynamically unstable patients or large area at risk: Consider insertion of intra-aortic balloon pump and emergency coronary angiography 1
• Critical caveat: The benefits of revascularization must be weighed against the risk of postoperative bleeding from periprocedural anticoagulation and post-revascularization antiplatelet therapy 4

For Non-ST-Elevation MI:

• Optimize medical therapy first 4
• Reserve catheterization for patients with recurrent instability, ongoing ischemia, or heart failure 2, 5
• Most patients should NOT be referred to emergency cardiac catheterization if MI is due to supply-demand mismatch 4, 2

Management of Mechanical Complications

• Sudden hemodynamic deterioration with low cardiac output or pulmonary edema requires immediate consideration of mechanical defects (ventricular septal defect, acute mitral regurgitation, free wall rupture) 1
• Listen for new cardiac murmur and obtain urgent transesophageal echocardiography 1
• These complications require emergency surgical intervention 1

Critical Pitfalls to Avoid

Do not routinely perform emergency angiography and revascularization in postoperative patients when MI is not related to acute coronary occlusion. 4 In cases of increased myocardial demand from postoperative tachycardia or hypertension, correcting these hemodynamic abnormalities is more beneficial and safer than invasive procedures 4.

Do not withhold aspirin before urgent CABG if this becomes necessary—aspirin is essential for preventing further thrombosis 1.

Prognostic Implications

• Intraoperative nonfatal MI carries extremely high mortality risk (40-70% for symptomatic MI) and substantially increases risk of future cardiac events dominated by cardiovascular death 2
• Patients presenting with perioperative MI have nearly one-third mortality or readmission rate at 30 days 2

Pre-Discharge Requirements

• Evaluate left ventricular function with echocardiography before hospital discharge 4, 1, 2
• Prescribe standard post-infarction medical therapy including aspirin, beta-blockers, ACE inhibitors, and high-intensity statin therapy 4, 1, 2
• Perform risk stratification with exercise testing or pharmacological stress testing to assess risk of further cardiovascular events 1, 2
• Implement aggressive cardiovascular risk factor modification including blood pressure control, smoking cessation, and management of diabetes and hyperlipidemia 1, 2