Can coronary artery bypass grafting (CABG) cause reperfusion ST elevation post-procedure?

Can CABG Cause Reperfusion ST Elevation Post-Procedure?

Yes, coronary artery bypass grafting can cause reperfusion ST elevation post-procedure as a manifestation of reperfusion injury, which occurs in approximately 25% of CABG patients and is associated with myocardial damage following restoration of coronary blood flow. 1

Mechanism and Pathophysiology

Reperfusion injury is a well-established phenomenon that occurs when coronary circulation is restored after CABG, particularly during the period following aortic cross-clamp removal. 2 The injury results from:

• Opening of the mitochondrial permeability transition pore during reperfusion, which uncouples oxidative phosphorylation and leads to cell death 3
• Release of cytokines, chemokines, oxidative stress mediators, and activation of inflammatory cascades during cardiopulmonary bypass 3
• Biochemical and microanatomic alterations affecting myocardial oxygen supply and demand 3

Clinical Evidence and Timing

Cardiac marker proteins demonstrate reperfusion injury as early as 0.5 hours after reperfusion begins, distinguishing it from postoperative myocardial infarction. 4 This early release pattern includes:

• Significantly elevated creatine kinase, creatine kinase-MB, fatty acid-binding protein, and myoglobin at 30 minutes post-reperfusion in patients undergoing CABG with cardiopulmonary bypass 4
• No such elevation in off-pump CABG patients, confirming the injury is related to the reperfusion process itself 4

Risk Factors for Reperfusion Injury

Patients at higher risk for reperfusion injury and associated ST elevation include those with:

• Preoperative NYHA Class III symptoms (p < 0.05) 1
• Coronary endarterectomy procedures (p < 0.01) 1
• Prolonged aortic cross-clamp time (p < 0.01) 1
• Active ongoing ischemia or infarction at the time of surgery 3

Distinguishing Reperfusion Injury from Acute Graft Failure

When ST elevation occurs post-CABG, urgent evaluation is critical:

• Immediate transthoracic echocardiography should be performed to rule out mechanical complications and assess ventricular function 5
• Emergency coronary angiography with potential PCI is indicated if graft failure is suspected with hemodynamic instability or cardiogenic shock 5
• Fatty acid-binding protein measurement can help distinguish early postoperative MI from reperfusion injury, as it rises 4 hours earlier than other markers in true MI 4

Important Clinical Caveats

Reperfusion injury is associated with concomitant myocardial infarction in 94% of cases (46 of 49 patients) where it contributes to fatal outcomes. 1 This highlights that ST elevation from reperfusion injury often coexists with actual myocardial damage rather than being a benign ECG finding.

CABG mortality is elevated for the first 3-7 days after myocardial infarction, and the timing of surgery relative to recent MI significantly impacts the risk of reperfusion injury. 3, 5

Management Implications

Despite intense research into pharmacological interventions targeting reperfusion injury components, none has been found efficacious for preventing this complication. 3 However:

• Ischemic postconditioning (three cycles of 1-minute ischemia/reperfusion after cross-clamp removal) may provide clinical benefits and maintain post-ischemic left ventricular performance 2
• Aspirin should be administered within 24 hours post-CABG unless contraindicated 5
• Avoid glucocorticoids and NSAIDs for post-CABG pericarditis as they are potentially harmful 5