What is the management of suspected perioperative myocardial infarction (MI) during coronary artery bypass grafting (CABG)?

Management of Perioperative Myocardial Infarction During CABG

Immediately optimize coronary arterial perfusion by targeting heart rate, diastolic/mean arterial pressure, and ventricular end-diastolic pressures to reduce ongoing ischemia and infarction. 1

Immediate Intraoperative Assessment

Perform intraoperative transesophageal echocardiography (TEE) immediately for evaluation of acute, persistent, and life-threatening hemodynamic disturbances that have not responded to treatment. 1, 2 This is a Class I recommendation that allows real-time assessment of:

• Regional wall motion abnormalities indicating acute ischemia 1
• Ventricular function and hemodynamic status 1
• Mechanical complications (papillary muscle rupture, ventricular septal defect) 1

TEE is reasonable for continuous monitoring of hemodynamic status, ventricular function, regional wall motion, and valvular function throughout the CABG procedure. 1

Hemodynamic Optimization Strategy

Target these specific parameters to maximize coronary perfusion: 1, 2

• Heart rate control: Maintain appropriate rate to optimize diastolic filling time 1
• Diastolic pressure: Maximize diastolic arterial pressure as this is the primary determinant of coronary perfusion 1
• Mean arterial pressure: Maintain adequate MAP for coronary perfusion 1
• Ventricular end-diastolic pressure: Optimize preload without causing excessive wall tension 1

Consider intra-aortic balloon counterpulsation for mechanical assistance to improve coronary perfusion in patients with persistent ischemia or hemodynamic instability. 1

Anesthetic Management

Use volatile anesthetic-based regimens as they can be useful in reducing the risk of perioperative myocardial ischemia and infarction (Class IIa recommendation). 1, 2 This approach has dual benefits of myocardial protection and facilitating early extubation. 1, 2

Decision Algorithm for Re-Revascularization

Emergency Coronary Angiography Indications

Proceed immediately to coronary angiography if any of the following are present: 1

1. Persistent ischemia of a significant myocardial area at rest AND/OR hemodynamic instability refractory to medical therapy 1
2. Cardiogenic shock (regardless of time from MI onset) 1
3. Life-threatening ventricular arrhythmias believed to be ischemic in origin 1
4. Acute mechanical complications: ventricular septal rupture, mitral valve insufficiency from papillary muscle infarction/rupture, or free wall rupture 1

Re-Revascularization Strategy Based on Angiographic Findings

If angiography reveals graft failure or native vessel occlusion: 3

• Emergency PCI is preferred if technically feasible, as it limits myocardial cellular damage compared to reoperation (peak troponin I: 81±18 ng/ml vs 178±62 ng/ml, p<0.001) 3
• Emergency reoperation is indicated when PCI is not feasible due to anatomy or when mechanical complications require surgical repair 1, 3
• Conservative management only if no significant graft failure is identified and patient is hemodynamically stable 3

Contraindications to Emergency Intervention

Do NOT proceed with emergency CABG or PCI if: 1

• Persistent angina with only a small area of viable myocardium and hemodynamic stability 1
• No-reflow state (successful epicardial reperfusion but unsuccessful microvascular reperfusion) 1
• Revascularization is impossible due to target anatomy 1
• Patient or designee does not wish further invasive care 1

Antiplatelet Management

For confirmed perioperative MI, consider dual antiplatelet therapy (DAPT) with aspirin plus clopidogrel despite the lack of strong evidence for mortality benefit. 4 While DAPT was not associated with reduced 30-day death, MI, or stroke in perioperative MI (adjusted HR not significant), it was associated with fewer all-cause re-hospitalizations (adjusted HR 0.71, CI 0.52-0.97, p=0.033). 4

Critical timing consideration: If clopidogrel was given preoperatively and bleeding complications occur, recognize that patients who underwent CABG <5 days after the last clopidogrel dose have significantly greater incidence of reoperation and major bleeding compared to those with >5 days washout. 5

Beta-Blocker Therapy

Reinstitute beta-blockers as soon as hemodynamically tolerated after perioperative MI. 2, 6 For patients with confirmed MI during CABG:

• Begin metoprolol 25-50 mg orally every 6 hours (depending on hemodynamic tolerance) once stable 6
• Advance to maintenance dose of 100 mg twice daily as tolerated 6
• Beta-blockers reduce postoperative atrial fibrillation and should be prescribed at discharge to all patients without contraindications 2

Prognostic Implications

Recognize that perioperative MI carries significant adverse outcomes: 7

• One-year vein graft failure occurs in 62.4% of patients with perioperative MI versus 43.8% without (p<0.001) 7
• Two-year composite outcome (death, MI, or revascularization) is worse: 19.4% versus 15.2% (adjusted HR 1.33,95% CI 1.00-1.76, p=0.046) 7
• In-hospital mortality ranges from 12-20% depending on re-revascularization strategy 3

Important caveat: Mechanisms other than vein graft failure account for a substantial proportion of perioperative MIs, suggesting that optimizing surgical technique, cardioplegia strategies, and perioperative hemodynamics is critical for prevention. 7

Common Pitfalls to Avoid

Do not delay TEE assessment when hemodynamic instability occurs—this is the only way to rapidly diagnose mechanical complications that require immediate surgical intervention. 1, 2

Do not perform emergency reoperation after failed PCI in the absence of ongoing ischemia or threatened occlusion, as this increases risk without benefit. 1

Do not use cyclooxygenase-2 inhibitors for postoperative pain relief, as these are potentially harmful after CABG. 1, 2

Avoid routine early extubation strategies in facilities with limited backup for airway emergencies when perioperative MI is suspected or confirmed. 1, 2