What is the recommended cardioplegia strategy for patients with low ejection fraction undergoing coronary artery bypass grafting (CABG)?

Cardioplegia Strategy for Patients with Low Ejection Fraction Undergoing CABG

In patients with low ejection fraction undergoing CABG, warm blood cardioplegia with prolonged reperfusion and a terminal "hot shot" is recommended to optimize myocardial protection and restore ventricular function. 1

Primary Cardioplegia Approach

Warm blood cardioplegia should be strongly considered as the preferred strategy in high-risk patients with poor ventricular function, as it improves postoperative left ventricular function compared to cold techniques. 1 The rationale is that dysfunctional myocardium in these patients is often "stunned" or "hibernating" rather than irreversibly damaged, and warm cardioplegia provides superior protection during revascularization. 1

Key Technical Components

• Prolonged reperfusion with terminal warm cardioplegia ("hot shot") should be employed to restore function in patients with poor ventricular function. 1 This controlled reperfusion strategy helps limit perioperative ischemic injury. 1

• Avoid cold injury and ensure homogeneous cardioplegic delivery, as inhomogeneous delivery may exacerbate perioperative ischemic injury and result in inadequate early postoperative ventricular function. 1

• Blood cardioplegia is preferred over crystalloid cardioplegia in patients with low ejection fraction to minimize hemodilution-related complications, particularly in those with anemia, low body surface area, or chronic kidney disease. 2

Alternative Modern Approaches

Recent evidence supports del Nido cardioplegia as an acceptable alternative in patients with reduced ejection fraction (EF ≤40%), showing equivalent short-term outcomes to conventional cold blood cardioplegia. 3, 4, 5

Del Nido Cardioplegia Advantages

• Provides satisfactory myocardial protection with similar biomarker release (troponin and CK-MB) compared to cold blood cardioplegia at 12 and 36 hours postoperatively. 4, 5

• Higher rate of spontaneous sinus rhythm return after cross-clamp release (80% vs. 48.9%, p=0.003) compared to cold blood cardioplegia. 4

• Significantly shorter cardiopulmonary bypass times (113.2 vs. 122.4 minutes, p=0.043) without compromising outcomes. 3

• Trend toward lower atrial fibrillation rates (6.7% vs. 17.8%, p=0.051) and lower CK-MB release at 36 hours. 4

Delivery Method Considerations

Combined antegrade and retrograde cardioplegia delivery should be considered for complex cases with extended cross-clamp times to ensure adequate distribution throughout the myocardium. 2

Critical Safety Parameters

• Maintain coronary sinus pressure between 30-50 mmHg when using retrograde cardioplegia to prevent venous injury, as pressures above 50 mmHg can cause coronary venous system damage. 2

• Avoid excessive antegrade delivery pressures to prevent endothelial damage. 2

• Ensure adequate distribution in patients with severe coronary disease or aortic valvular insufficiency, as these conditions can lead to uneven myocardial protection. 2

Adjunctive Pharmacological Support

Perioperative levosimendan administration should be considered to reduce the risk of low cardiac output syndrome in patients with reduced left ventricular ejection fraction undergoing isolated CABG (Class IIa, Level A). 1 This calcium sensitizer improves outcomes without significantly increasing myocardial oxygen consumption. 1

Common Pitfalls to Avoid

• Do not use crystalloid cardioplegia as first-line in patients with low ejection fraction due to significant hemodilution causing decreased oxygen-carrying capacity, greater blood loss, and higher transfusion requirements. 2

• Avoid interruption of cardioplegia delivery during normothermic techniques, as this can induce anaerobic metabolism and warm ischemic injury. 2

• Monitor for hyperkalemia upon reperfusion from high potassium concentrations in cardioplegia solutions. 2

• Be vigilant about glucose-containing cardioplegia solutions as they may exacerbate perioperative hyperglycemia, which is associated with adverse outcomes including atrial fibrillation and longer ICU stays. 2

Expected Outcomes

With appropriate cardioplegia strategies, patients with severely impaired left ventricular function (EF ≤30%) can achieve:

• 30-day mortality of 2-4.8% with modern techniques. 6, 7
• Significant improvement in postoperative ejection fraction (mean improvement from 15.7% to 22.6%, p<0.0002). 6
• Similar perioperative outcomes to conventional techniques when del Nido is used, including comparable rates of stroke, myocardial infarction, and major adverse cardiac events. 4, 5