Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery
George Krasopoulos1,2, Andrea D'Alessio1, Danilo Verdichizzo1
1Department of Cardiothoracic Surgery, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.
Insights
Graft flow in coronary artery bypass grafting (CABG) is influenced by pre-operative flow and patient sex. Male patients demonstrated higher graft flows, highlighting factors affecting surgical outcomes.
Area of Science:
- Cardiovascular Surgery
- Vascular Physiology
- Surgical Outcomes
Background:
- Long-term outcomes in coronary artery bypass grafting (CABG) depend on arterial graft physiology.
- Internal mammary artery grafts to the left anterior descending artery are crucial for CABG success.
- Understanding factors influencing graft resistance to flow is essential for improving CABG procedures.
Purpose of the Study:
- To investigate factors affecting arterial graft flow and resistance in CABG patients.
- To analyze the impact of pre-operative flow, patient demographics, and graft characteristics on graft performance.
- To introduce novel concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.
Main Methods:
- Prospective, nonrandomized observational study of 100 consecutive patients undergoing CABG.
- Assessment of coronary stenoses using conventional and quantitative coronary angiography.
- Measurement of graft flow and pulsatility index (PI) using transit-time flowmetry.
- Statistical analysis including fractional polynomials and multivariable regression.
Main Results:
- Higher end-of-operation graft flows were associated with higher cross-clamp on flows, male sex, lower end-of-operation PI, and larger recipient artery size.
- Multivariable analysis confirmed significant associations between end-of-operation graft flow, cross-clamp on flow, sex, and end-of-operation PI.
- Concomitant valve surgery did not significantly impact graft flows; male patients exhibited 18 mL/min higher flow.
Conclusions:
- Graft flow at the end of CABG is predictable by pre-operative flow (cross-clamp on) and post-operative PI (cross-clamp off).
- Significant sex-based differences in graft flow were observed, with males having higher flows.
- The study introduces "adequate flow" and "resistance-to-forward-flow" as key metrics for evaluating patent coronary grafts.
Introduction:
Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery.
Methods:
This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis.
Results:
Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow.
Conclusions:
The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.
