# Should we ligate coronary conduits when flow measurements indicate competitive flow? a case report

## TL;DR

A case report discusses how competitive flow in coronary bypass grafting can lead to functional graft occlusion and highlights the importance of adjusting surgical plans based on flow measurements.

## Contribution

The paper presents a novel clinical case and rationale for ligating grafts based on competitive flow measurements during coronary artery bypass grafting.

## Key findings

- High backward flow values in TTFM suggest competitive flow even with otherwise normal parameters.
- Proximal LAD stenosis near a grafted diagonal branch increases the risk of functional graft occlusion.
- Adjusting revascularization plans based on TTFM can improve patient outcomes.

## Abstract

Competitive flow (CF) in coronary artery bypass grafting (CABG) occurs when graft flow is impaired due to higher competing flow from either the native circulation or another graft and may result in functional graft occlusion. We report a case of functional graft occlusion of a left internal mammary artery (LIMA) due to flow competition with a saphenous vein graft (SVG) and discuss the rationale of ligating the graft responsible for the CF.

The case refers to a 56-year-old man with an isolated subtotal ostial left anterior descending (LAD) lesion who underwent conventional double on-pump CABG with an in situ (LIMA) to the LAD and a centrally anastomosed SVG to the Diagonal branch (D1). Concerning the initial Transit-time flow measurements (TTFM), the SVG had a mean graft flow (MGF) of 49 ml/min, a Pulsatility index (PI) of 1 and a Diastolic flow (DF) of 66%. The LIMA graft had an MGF of 31 ml/minute, a PI of 3.8, a DF of 80%, but a Backward flow (BF) of 8%. As the LIMA BF was quite high, we suspected competitive flow of the graft and thus decided to transiently apply a bulldog clamp to the SVG, to check if the LIMA TTFM would change. Indeed, MGF was 44 ml/minute, the PI was 2.3, DF was 60%, and BF was 0.9%. Despite these results, the operating surgeon did not alter the revascularization plan and the operation was finished. The patient was discharged uneventfully. However, in a 6-month follow-up, the patient was symptomatic and with poor ejection fraction, and the diagnostic work-up revealed the functional occlusion of the LIMA graft with a string sign, and a patent SVG. After Heart Team consultation and patient update, he underwent left main stent implantation.

There should be a great degree of suspicion for CF with high BF values, even when the rest of the parameters measured during TTFM are normal or marginal. Also, the location of the LAD stenosis proximal to the D1 is a risk factor for CF when both arteries are grafted. Changing the revascularization plan based on TTFM is warranted for optimal outcomes.

The online version contains supplementary material available at 10.1186/s13019-025-03529-0.