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The effect of protamine on the epicardial microflow and the graft flow in open-heart surgery
1Department of Thoracic and Cardiovascular Surgery, University of Göteborg, Sahlgrenska University Hospital, Sweden.
Insights
Coronary artery bypass grafting enhances myocardial microcirculation and graft flow. Protamine administration may reduce graft flow post-surgery, suggesting a need for alternative heparin reversal methods.
Area of Science:
- Cardiovascular Surgery
- Myocardial Perfusion Assessment
- Surgical Outcomes
Background:
- Assessing myocardial perfusion and graft flow is crucial for evaluating surgical success in coronary artery bypass grafting (CABG).
- Laser Doppler flowmetry (LDF) and electromagnetic flowmetry are key techniques for measuring microcirculation and graft flow, respectively.
Purpose of the Study:
- To evaluate the impact of coronary revascularization on myocardial perfusion and surgical outcomes.
- To assess graft flow dynamics following coronary artery bypass grafting (CABG) and valve replacement (VR) procedures.
Main Methods:
- Utilized laser Doppler flowmetry (LDF) to measure epicardial microcirculation in patients undergoing CABG or valve replacement (VR).
- Employed electromagnetic flowmetry to measure graft flow in the CABG group.
- Correlated LDF and graft flow measurements at various postoperative time points.
Main Results:
- CABG significantly increased myocardial microcirculation (LDF) post-cardiopulmonary bypass (CPB) and after protamine infusion.
- Graft flow also increased post-protamine but subsequently decreased, indicating a potential negative impact of protamine.
- A strong positive correlation was observed between LDF and graft flow in the CABG group.
Conclusions:
- Coronary bypass grafting improves myocardial microcirculation, with graft flow serving as an early indicator of surgical effectiveness.
- Protamine administration is implicated in postoperative graft flow reduction, highlighting the need for alternative heparin reversal strategies.
Abstract:
To evaluate the effect of coronary revascularization on myocardial perfusion and surgical outcome regarding graft flow, we used laser Doppler flowmetry to assess the epicardial microcirculation in patients undergoing coronary artery bypass grafting (CABG) or valve replacement (VR) and electromagnetic flowmetry to measure graft flow in the CABG group. In the CABG group, the preoperative mean laser Doppler flow rate (LDF) in the epicardium of the left ventricle significantly increased at the end of cardiopulmonary bypass (CPB) (22 +/- 7 arbitrary units (AU) to 60 +/- 13 AU, p < 0.001). This value further increased 10 min after protamine infusion (66 +/- 14 AU, p < 0.01), but was significantly reduced 30 min later (51 +/- 14 AU, p < 0.002). Compared to the post-CPB value (34 +/- 10 ml/min) before protamine infusion, the mean graft flow (ml/min) to this area significantly increased 10 min after protamine infusion (41.3 +/- 10 ml/min, p < 0.001) but significantly decreased 30 min later (29 +/- 9 ml/min, p < 0.001). The preoperative mean LDF in the VR group was significantly higher than in the CABG group (p < 0.01). In the CABG group, there was a positive correlation between the LDF and graft flow at the end of CPB (r = 0.788) and 10 (r = 0.767) and 30 (r = 0.784) min after protamine infusion. This study shows that coronary bypass grafting increases the myocardial microcirculation which, together with graft flow, could give an early indication of the effect of surgery on myocardial microcirculation. Furthermore, protamine was found to be one of the factors contributing to graft flow reduction postoperatively and, therefore, newer methods of heparin reversal may be desirable.