What is the management of delayed arrhythmia post coronary artery bypass graft (CABG)?

Management of Delayed Arrhythmia Post-CABG

For patients with new-onset symptomatic bradycardia (sick sinus syndrome or advanced AV block) that persists 5-7 days after isolated CABG, permanent pacemaker implantation is recommended before discharge. 1

Bradyarrhythmias (Conduction Defects)

Initial Assessment and Temporary Management

• Temporary epicardial pacing wires placed during surgery serve as the bridge for managing postoperative conduction abnormalities, with an 8.6% overall need for temporary pacing support 1
• Monitor for new-onset sick sinus node dysfunction (SND) or atrioventricular block, which occur in 2-58% of patients depending on surgical factors including direct conduction system damage, myocardial ischemia, or inadequate myocardial protection 1

Indications for Permanent Pacing

• Permanent pacemaker implantation (Class I recommendation) is indicated when new postoperative SND or AV block causes persistent symptoms or hemodynamic instability that does not resolve after surgery 1
• Timing: 5-7 days post-surgery is reasonable for permanent pacemaker placement when conduction abnormalities persist, facilitating ICU discharge, ambulation, and anticoagulation initiation when necessary 1
• Preoperatively existing conduction abnormalities with symptomatic bradycardia will generally not resolve with CABG alone and require pacing 1

Special Considerations

• Patients with severe left ventricular dysfunction and accompanying left bundle branch block may benefit from temporary cardiac resynchronization therapy using right atrial, right ventricular, and left ventricular epicardial wires in the immediate postoperative period 1
• For patients likely to require future cardiac resynchronization therapy (CRT), consider intraoperative placement of a permanent epicardial left ventricular lead (Class IIb recommendation) 1

Atrial Fibrillation

Acute Management Strategy

Initial management prioritizes ventricular rate control over immediate rhythm conversion, as early cardioversion attempts are often unsuccessful and poorly tolerated immediately post-surgery 2, 3

Rate Control Approach

• Beta-adrenergic blockers are the most effective first-line agents for both rate control and rhythm conversion in post-CABG atrial fibrillation, superior to other antiarrhythmic drugs in this specific setting 2, 3
• Intravenous diltiazem serves as an alternative calcium channel blocker for rate control, though less extensively studied than beta-blockers post-CABG 2
• Digoxin, amiodarone, and sotalol are surprisingly less effective for post-CABG atrial fibrillation compared to beta-blockers 2

Rhythm Control

• Delay elective cardioversion (electrical or pharmacological) for as long as clinically tolerable after surgery, as spontaneous conversion is common 2, 3
• Reserve Class IA and III antiarrhythmic drugs for persistent, poorly tolerated, or prolonged episodes of atrial fibrillation 2
• Immediate cardioversion is indicated only for hemodynamically unstable or severely symptomatic patients 4, 2

Anticoagulation Decision-Making

• Anticoagulate after cardioversion or if atrial fibrillation persists >48 hours in patients with stroke risk factors 4, 3
• Minimum duration: 4 weeks of anticoagulation is recommended, but longer duration should be considered in patients at high stroke risk regardless of atrial fibrillation recurrence 4
• Anticoagulation for post-CABG atrial fibrillation balances thromboembolism risk (including stroke) against bleeding risk in the early postoperative period 4, 2, 3

Timing and Natural History

• Atrial fibrillation typically occurs in paroxysms between postoperative days 2-5, with prevalence of 15-45% after CABG 4, 2, 3
• Most cases are self-limited and benign, though they increase morbidity, cost, and length of hospital stay 2, 3
• Sinus rhythm is typically achieved before extubation in the majority of patients 5

Ventricular Arrhythmias

Risk Stratification

• Sustained ventricular tachycardia/ventricular fibrillation occur infrequently (<2% of patients) but carry high mortality rates 3
• Simple ventricular arrhythmias are common after CABG and do not affect prognosis, requiring no specific intervention 3

Management of Life-Threatening Ventricular Arrhythmias

• Correct precipitating factors first, particularly myocardial ischemia, electrolyte abnormalities, and inadequate myocardial protection 3
• CABG is recommended (Class I) for patients with resuscitated sudden cardiac death or sustained ventricular tachycardia caused by significant CAD (>50% left main or >70% stenosis of epicardial vessels) with resultant myocardial ischemia 1
• Implantable cardioverter-defibrillator (ICD) implantation should be considered for survivors of sustained VT/VF after CABG, as revascularization may not eliminate all arrhythmogenic substrates 1, 3
• Electrophysiologically guided drug therapy may be appropriate for select patients surviving initial ventricular arrhythmia events 3

Contraindication

• CABG should not be performed (Class III: Harm) in patients with ventricular tachycardia with scar and no evidence of ischemia 1

Common Pitfalls to Avoid

• Do not delay permanent pacemaker placement beyond 5-7 days in patients with persistent symptomatic bradycardia, as this prolongs ICU stay and delays mobilization 1
• Avoid premature cardioversion of atrial fibrillation in the immediate postoperative period; opt for rate control initially 2
• Do not withhold anticoagulation in persistent atrial fibrillation >48 hours with stroke risk factors due to concerns about bleeding—the stroke risk often outweighs bleeding risk after the first 48-72 hours 4, 3
• Recognize that preoperative beta-blockers may not independently prevent post-CABG atrial fibrillation despite guideline recommendations, though they remain effective for acute management 6