What is considered a long cardiopulmonary bypass (CPB) time for mitral valve replacement and maze procedure with left atrial appendage excision?

Cardiopulmonary Bypass Time Considerations for Mitral Valve Replacement with Maze and LAA Excision

For combined mitral valve replacement, full maze procedure, and left atrial appendage excision, cardiopulmonary bypass (CPB) times exceeding 2 hours should be considered prolonged, with aortic cross-clamp times beyond 120 minutes warranting serious consideration for conversion to a simpler approach or staged completion. 1

Specific Time Thresholds

Cross-Clamp Time Limits

• Maximum recommended cross-clamp time is 2 hours (120 minutes), particularly in robotic-assisted or minimally invasive approaches 1
• Even shorter cross-clamp times are advisable in patients with impaired ventricular function 1
• Designating a team member to impose a "hard stop" after predetermined time limits allows for safe conversion and completion of the operation 1

Expected CPB Times for Combined Procedures

• Mitral valve repair alone with maze: 150-174 minutes mean CPB time 2, 3
• The maze procedure adds approximately 21 minutes of additional cross-clamp time to mitral valve surgery 4
• Cross-clamp times for mitral valve repair with maze: 95-122 minutes mean 2, 3
• Adding left atrial appendage excision is considered a simpler concurrent procedure that adds minimal time compared to the full biatrial maze 1

Procedural Complexity Hierarchy

Progression of Surgical Experience Required

Surgeons should gain proficiency with simpler concurrent procedures before attempting complex combinations 1:

1. Simple procedures (minimal added time):

   • Patent foramen ovale closure through the left atrium 1
   • Pulmonary vein isolation 1
   • Left atrial appendage closure 1

2. Complex procedures (significant added time):

   • Full biatrial Cox-maze procedures 1
   • Concurrent tricuspid valve repair 1

Performing concurrent procedures may prolong already extended perfusion and clamp times, requiring significant experience with primary isolated procedures and consistently shorter clamp times before attempting combinations 1

Critical Safety Considerations

Complications Associated with Prolonged Times

• Unilateral pulmonary edema is a rare but life-threatening complication most commonly associated with prolonged perfusion and cross-clamp times, occurring early in a team's learning curve 1
• Extended bypass times increase risk of:
  • Inadequate myocardial protection 1
  • Increased bleeding requiring re-exploration 2, 3
  • Postoperative bradycardia requiring permanent pacing 1, 5, 4

Conversion Criteria

Immediate conversion to sternotomy is warranted when:

• Cross-clamp time approaches or exceeds 2 hours 1
• Inadequate myocardial protection occurs (heart not electrically quiet, asystolic, or cold) 1
• Poor visualization compromises mitral valve exposure 1

Comparative Data from Research Studies

Actual Reported Times

Studies comparing mitral valve surgery with and without maze procedure demonstrate 2, 3:

• CPB time increased by 24-30 minutes when adding maze to mitral valve repair
• Cross-clamp time increased by 27-30 minutes when adding maze to mitral valve repair
• Despite longer times, no increase in hospital mortality was observed in experienced hands 2, 3

Full Maze vs. Mini-Maze Considerations

• Full biatrial maze procedure (Cox-maze III or IV) provides 75-95% success rates for sinus rhythm conversion but requires longer operative times 1, 5
• Less extensive "mini-maze" procedures (pulmonary vein isolation alone or left-sided only) are less effective (10-40% success) but reduce operative time 1
• The full maze is preferable when feasible, despite longer times, due to superior efficacy 1

Practical Time Management

For mitral valve replacement with full maze and LAA excision, anticipate:

• Total CPB time: 170-200 minutes
• Cross-clamp time: 100-140 minutes
• Times exceeding these ranges should trigger reassessment of technique, consideration for conversion, or acceptance that the team is still on the learning curve 1, 2, 3