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Do coronary bypass graft flows differ between on-pump and off-pump operations?
Yves A G Louagie1, Jacques Jamart, André Gruslin
1Department of Cardiovascular and Thoracic Surgery, University Clinics of Mont Godinne, Université Catholique de Louvain, Yvoir, Belgium. louagie@chir.ucl.ac.be
Insights
Off-pump coronary bypass surgery shows lower graft flow velocity and higher resistance compared to on-pump surgery, primarily due to hematocrit changes from hemodilution.
Area of Science:
- Cardiovascular Surgery
- Hemodynamics
- Bypass Grafting
Background:
- Coronary artery bypass grafting (CABG) is a common procedure.
- On-pump CABG uses cardiopulmonary bypass, while off-pump CABG does not.
- Hemodynamic differences between these techniques require investigation.
Purpose of the Study:
- To compare hemodynamic parameters in coronary bypass grafts between on-pump and off-pump CABG.
- To identify factors influencing graft performance in both surgical approaches.
Main Methods:
- Two propensity score-matched cohorts of 89 patients each were analyzed.
- 408 dual beam Doppler flow measurements were obtained from patent, single terminolateral bypass grafts.
- Hemodynamic factors including flow, velocity, resistance, and pulsatility index were measured.
Main Results:
- Off-pump grafts exhibited lower flow velocity (20.5 cm/s vs 23.8 cm/s) and higher resistance (1.76 vs 1.50 mm Hg/(mL/min(-1))) compared to on-pump grafts (p<0.05).
- Hematocrit levels were significantly higher in the off-pump group (32.9% vs 23.5%, p<0.001).
- Hematocrit was the primary determinant of flow and velocity, with no significant differences in graft hemodynamics when hematocrit was matched.
Conclusions:
- Off-pump CABG is associated with reduced graft flow velocity and increased resistance, largely attributable to hemodilution-induced changes in hematocrit and viscosity.
- These findings highlight the impact of intraoperative fluid management on graft performance.
- Optimizing hematocrit may be crucial for improving off-pump graft outcomes.
Background:
The aim of this study is to compare hemodynamic factors in coronary bypass grafts on-pump and off-pump.
Methods:
Two propensity score-matched groups of 89 patients each including 408 dual beam Doppler flow measurements were compared. The study included only patent and single terminolateral bypass grafts.
Results:
Flow was 64.9 +/- 37.3 mL/min in the on-pump group versus 58.6 +/- 35.0 mL/min in the off-pump group (p = 0.063); velocity was 23.8 +/- 10.5 versus 20.5 +/- 10.4 cm/s (p = 0.004); resistance measured as mm Hg/(mL/min(-1)) was 1.50 +/- 1.09 versus 1.76 +/- 1.14 (p = 0.020); pulsatility index was 1.98 +/- 1.52 versus 2.44 +/- 1.62 (p = 0.004). The hematocrit was 23.5 +/- 3.8% in the on-pump and 32.9 +/- 4.1% in the off-pump groups (p < 0 0.001). Multivariate analysis showed that hematocrit was the most significant factor influencing flow (p < 0.001) and velocity (p < 0.001), along with resistance (p = 0.004) and pulsatility index (p < 0.001). In a subset of 50 hemodynamic measurements made on left internal thoracic arteries implanted onto left anterior descending arteries and matched for hematocrit, there were no differences between on-pump and off-pump groups regarding flow, velocity, resistance, or pulsatility index.
Conclusions:
Off-pump compared with on-pump bypass surgery is associated with lower velocity and higher resistance in the grafts, mainly caused by changes in hematocrit and viscosity related to hemodilution.
