What is the role of an epicardial pacemaker (electrode implanted directly on the heart) in managing cardiac arrest post open heart surgery?

Role of Epicardial Pacing in Cardiac Arrest Post Open Heart Surgery

Epicardial pacing is a critical intervention for managing cardiac arrest following open heart surgery, particularly for bradyarrhythmias and asystole, and should be implemented before external cardiac massage when immediately available.

Indications and Rationale

• Temporary epicardial pacing wires should be routinely placed during all open heart surgeries to manage potential postoperative arrhythmias that could lead to cardiac arrest 1
• Arrhythmias are extremely common after cardiac surgery, with ventricular arrhythmias occurring frequently in the immediate postoperative period due to hypothermia, ischemia, and electrolyte abnormalities 1
• The risk of heart block requiring temporary or permanent pacing is highest in the immediate postoperative period, with permanent pacemaker implantation required in approximately 1.5% of all cardiac surgery cases 1

Protocol for Cardiac Arrest Management Post Cardiac Surgery

• In asystole or extreme bradycardia, pacing (where immediately available via epicardial wires) should precede external cardiac massage 2
• For ventricular fibrillation, three sequential defibrillation attempts should be performed before initiating external cardiac massage 2
• If pacing and defibrillation fail to restore circulation, early resternotomy should be considered, particularly in pulseless electrical activity 2

Specific Pacing Considerations by Surgery Type

After Valve Surgery

• Patients undergoing mitral valve surgery have a 1-9% risk of requiring permanent pacing 1
• Tricuspid valve surgery carries an even higher risk of postoperative conduction disorders, making epicardial pacing particularly important 1
• Aortic valve procedures frequently affect the His bundle, potentially requiring temporary or permanent pacing 1

After Surgery for Atrial Fibrillation

• Patients undergoing surgery for atrial fibrillation should have routine placement of temporary epicardial pacing wires 1
• Up to 11% of patients undergoing a Cox Maze IV procedure with mitral valve surgery require postoperative permanent pacemaker implantation 1

Technical Aspects of Epicardial Pacing

• Epicardial pacing involves direct electrode placement on the heart's surface during surgery, allowing for immediate electrical stimulation when needed 3
• Dual chamber temporary pulse generators offer sophisticated pacing options that can be tailored to the patient's specific arrhythmia 3
• Pacing parameters should be optimized to avoid complications such as oversensing, undersensing, cross-talk, and pacemaker-mediated tachycardia 3

Timing and Duration

• For patients with new postoperative sinus node dysfunction or atrioventricular block associated with symptoms or hemodynamic instability that does not resolve after surgery, permanent pacing is recommended before discharge 1
• The timing of permanent pacemaker implantation has not been formally studied but 5-7 days post-surgery is generally considered reasonable 1

Limitations and Complications

• External cardiac pacing is not effective as routine treatment in patients with asystolic cardiac arrest of prolonged duration 1, 4
• Epicardial pacing wires can rarely cause life-threatening complications such as hemorrhage during removal 5
• The effectiveness of pacing in cardiac arrest diminishes significantly with time from arrest onset 4

Risk Factors for Requiring Pacing

• Prolonged cross-clamping time and larger volumes of cardioplegic agent during surgery are significant predictors of temporary pacemaker need 6
• Other risk factors include preoperative conduction abnormalities (RBBB, LBBB, PR interval >200 ms), multivalve surgery (particularly involving the tricuspid valve), prior valve surgery, age >70 years, and reoperations 1

By understanding these principles and implementing them promptly, the management of cardiac arrest following open heart surgery can be optimized to improve patient outcomes and survival.