What are the intra‑operative complications of off‑pump coronary artery bypass grafting (OPCAB) and their management?

Intraoperative Complications During Off-Pump CABG and Their Management

Primary Intraoperative Complications

The two major intraoperative complications during OPCAB are hemodynamic instability during cardiac manipulation and dysrhythmias, both requiring immediate recognition and aggressive management to prevent conversion to emergency on-pump surgery. 1, 2

Hemodynamic Instability

Hemodynamic compromise occurs primarily during heart enucleation and positioning required to access different coronary territories, particularly the lateral and posterior vessels. 2

• Inotropic support is required in 30% of OPCAB cases compared to only 15% in on-pump CABG, representing a doubling of the need for pharmacologic hemodynamic support 1
• The instability results from decreased venous return and cardiac output when the heart is lifted and rotated to expose target vessels 2
• Management requires:
  • Aggressive volume loading prior to cardiac manipulation 2
  • Immediate inotropic support (dobutamine or milrinone) when cardiac output falls 1, 2
  • Trendelenburg positioning to improve venous return 2
  • Immediate conversion to on-pump bypass if hemodynamics cannot be stabilized, as patients with hemodynamic compromise should undergo on-pump CABG 3

Intraoperative Dysrhythmias

Dysrhythmias occur in 15% of OPCAB cases versus only 3.5% in conventional CABG, representing a more than 4-fold increase in arrhythmic complications. 1

• Ventricular arrhythmias are triggered by mechanical irritation during cardiac manipulation and regional ischemia during coronary occlusion 1, 2
• Atrial fibrillation occurs in 43% of high-risk OPCAB patients versus 22% in low-risk patients 4
• Management approach:
  • Prophylactic beta-blockers reduce AF incidence from 40% to 20% and should be continued perioperatively 5
  • For acute ventricular arrhythmias: immediate defibrillation if unstable, lidocaine bolus if stable 2
  • For hemodynamically significant AF: short-acting beta-blockers (esmolol) or amiodarone 5
  • If dysrhythmias persist despite medical management, immediate conversion to on-pump bypass is required 1

Myocardial Ischemia During Grafting

Regional myocardial ischemia is unavoidable when coronary flow is interrupted during anastomosis construction, requiring specific protective strategies. 2

• Volatile anesthetics (sevoflurane, desflurane) provide marked cardioprotection against ischemia and are specifically indicated for OPCAB 2
• Intracoronary shunts should be used when available to maintain distal perfusion during anastomosis 2
• Minimize ischemic time by efficient surgical technique and proper stabilization 2
• Monitor for ST-segment changes and new wall motion abnormalities on TEE 2

Embolic Complications and Stroke Prevention

The primary advantage of OPCAB is stroke reduction, but this benefit is only realized when aortic manipulation is completely avoided using clampless/anaortic techniques. 6, 3

Aortic Manipulation Risks

• Standard OPCAB with partial aortic clamping produces significantly more solid microemboli on transcranial Doppler than clampless surgery 6
• Clampless off-pump CABG reduces stroke risk by 64% (OR = 0.36,95% CI: 0.13–0.99) compared to conventional techniques 6
• Complete avoidance of aortic manipulation further reduces stroke, atrial fibrillation, and acute renal failure compared to OPCAB with aortic clamping 7

Management Strategy

• Use all-arterial grafting with in-situ grafts (LIMA, RIMA) to avoid proximal anastomoses on the aorta 6, 7
• If vein grafts are necessary, use clampless proximal anastomotic devices (HeartString) 6
• Perform epiaortic ultrasound to identify atherosclerotic disease and avoid manipulation of diseased segments 6
• Patients with severe ascending aortic atherosclerosis represent the strongest indication for complete anaortic OPCAB 3

Incomplete Revascularization

OPCAB is associated with higher rates of incomplete revascularization due to technical difficulty accessing certain coronary territories, particularly lateral wall vessels. 6, 3

• Fewer distal anastomoses are performed with complete anaortic technique (3.2 ± 0.9) compared to conventional CABG (3.7 ± 0.9) 7
• Incomplete revascularization results in reduced long-term survival 6
• Management approach:
  • Use optimal stabilization devices (Donut Heart Stabilizer) to access all territories 8
  • Convert to on-pump if complete revascularization cannot be achieved off-pump 3
  • Consider hybrid revascularization with PCI for inaccessible vessels 6

Graft Patency Issues

Inferior graft patency is a major concern with OPCAB, with 27% higher risk of graft occlusion compared to on-pump CABG. 6, 3

• One-year graft patency is 82.6% for OPCAB versus 87.8% for on-pump CABG 6, 3
• Technical difficulty on the beating heart contributes to suboptimal anastomoses 6, 3
• Intraoperative management:
  • Use intraoperative graft assessment with SPY fluorescence imaging to detect failed grafts immediately 8
  • Revise any graft with poor flow or technical issues before closing 8
  • Ensure adequate stabilization to create motionless operative field 8

High-Risk Patient Considerations

High-risk patients (EuroSCORE >5) experience significantly more complications during OPCAB despite theoretical benefits. 4

• Blood transfusion required in 70% of high-risk versus 31% of low-risk patients 4
• Intraaortic balloon pump insertion needed in 16% of high-risk versus 3% of low-risk patients 4
• Renal failure occurs in 13% of high-risk versus 3% of low-risk patients 4
• Mortality is 9% in high-risk versus 0% in low-risk OPCAB patients 4
• Management implications:
  • Have IABP immediately available for high-risk cases 4
  • Maintain lower threshold for conversion to on-pump bypass 4
  • OPCAB should only be performed by surgeons with extensive experience 3

Critical Pitfall: Conversion to Emergency On-Pump

The conversion rate from OPCAB to emergency on-pump surgery is 11.8%, representing a high-risk situation requiring immediate team coordination. 1

• Indications for conversion include refractory hemodynamic instability, uncontrolled dysrhythmias, or inability to access target vessels 1, 2
• Have perfusion team immediately available with primed bypass circuit 6
• Recognize that delayed conversion increases mortality 1