Can heart block occur post-operatively?

From the Guidelines

Yes, heart block can occur post-operatively, particularly after cardiac surgeries such as valve replacements and coronary artery bypass grafting. This complication may be temporary or permanent, ranging from first-degree (prolonged PR interval) to complete heart block (no conduction between atria and ventricles) 1. Risk factors include pre-existing conduction abnormalities, advanced age, electrolyte disturbances, hypothermia during surgery, and direct trauma to the conduction system during procedures.

Post-Operative Heart Block Management

Management depends on the severity and symptoms, with temporary pacing often used for significant bradycardia. Asymptomatic first-degree block typically requires monitoring only, while symptomatic higher-degree blocks may need temporary pacing wires placed during surgery. If the block persists beyond 7-10 days, permanent pacemaker implantation is usually considered, as indicated by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.

Causes of Post-Operative Heart Block

Post-operative heart block occurs because surgical manipulation, inflammation, or edema can damage or irritate the heart's electrical conduction pathways, particularly the atrioventricular node or bundle branches, disrupting the normal electrical signals that coordinate heartbeats. The assessment of bradyarrhythmias in this setting is often complicated by the coexistence of atrial tachyarrhythmia, transient and time-dependent postoperative effects on sinus and atrioventricular node function, and the potential presence of antiarrhythmic drugs 1.

Key Considerations

• The incidence of post-operative atrial fibrillation (AF) can range from 10% to 65%, with a peak incidence 2 to 4 days postoperatively 1.
• Permanent pacemaker implantation is required in 1.5% of cases for postoperative atrioventricular block after cardiac surgery 1.
• Predictors of postoperative pacing include preoperative first-degree atrioventricular block with and without left anterior fascicular block and/or intraventricular conduction delay, postoperative cardiac arrest, and combined mitral and aortic valve replacements 1.
• The 2018 ACC/AHA/HRS guideline recommends a period of watchful waiting rather than early PPM implantation for bradyarrhythmias in the setting of postoperative AF, treating them similarly to those occurring in the nonoperative setting 1.

From the Research

Heart Block After Surgery

• Heart block can occur after surgery, as reported in several studies 2, 3, 4, 5, 6.
• The incidence of heart block after surgery varies, with one study reporting an incidence of 1% in pediatric patients after congenital heart surgery 2.
• Another study found that 2% of patients who underwent cardiac surgery developed post-operative heart block, with 0.6% requiring pacemaker placement 5.
• Risk factors for heart block after surgery include:
  • Type of surgery, such as mitral valve surgery 6
  • Implantation of bioprosthetic devices 6
  • Age over 60 years 6
  • Prior use of anti-arrhythmic drugs 6
  • Previous use of beta-blockers 6
• Heart block after surgery can be associated with increased mortality, as reported in one study 2.
• However, another study found that the presence of atrio-ventricular block did not significantly increase mortality, but did prolong hospital length-of-stay and increase hospital costs 6.
• Some patients who develop heart block after surgery may experience recovery of atrioventricular node function, with one study reporting a recovery rate of 70% 5.
• Factors associated with recovery of atrioventricular node function include:
  • Single-ventricle physiology 5
  • Greater weight at the time of surgery 5
  • Shorter cardiopulmonary bypass time 5