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. 2021 May 10;32(5):711-718.
doi: 10.1093/icvts/ivaa328.

A new way to use transit-time flow measurement for coronary artery bypass grafting

Lukas Stastny  1 , Markus Kofler  1 , Vitalijs Zujs  1 , Elfriede Ruttmann  1 , Julia Dumfarth  1 , Juliane Kilo  1 , Alexandra Brix  1 , Simone Gasser  1 , Adel Sakic  1 , Thomas Schachner  1 , Michael Grimm  1 , Nikolaos Bonaros  1
Affiliations

A new way to use transit-time flow measurement for coronary artery bypass grafting

Lukas Stastny et al. Interact Cardiovasc Thorac Surg. .

Abstract

Objectives: Transit-time flow measurement is a recognized method for graft evaluation in coronary surgery. However, single flow measurement has been associated with a low specificity for detecting graft dysfunction. The goal of this study was to assess the value of transit-time flow measurement for assessing in situ internal mammary artery grafts during non-existent native coronary circulation and the relevance of collateral blood flow in target vessels.

Methods: Between 2014 and 2018, a total of 134 patients undergoing on-pump coronary artery bypass grafting were evaluated using transit-time flow measurement. We analysed 111 single left internal mammary artery and 57 single right internal mammary artery bypasses. Correlations between coronary relevant parameters were calculated using Spearman's ρ coefficient. Risk factors for decreased flow with an arrested heart (FAH) <30 ml/min and an increased pulsatility index (PI) >3.0 as well as flow reduction >30% were calculated.

Results: FAH correlated with the diameter of the target vessel (Spearman's ρ = 0.32; P < 0.001), the amount of blood distribution (Spearman's ρ = 0.34; P < 0.001), the PI (Spearman's ρ = 0.19; P = 0.019) and the degree of stenosis (Spearman's ρ = -0.17; P = 0.042). The percentage of flow change was found to correlate with the PI (Spearman's ρ = -0.47; P < 0.0001), the degree of stenosis (Spearman's ρ = 0.42; P < 0.001), the diameter of the target vessel (Spearman's ρ = -0.22; P = 0.008) and the area of blood distribution (Spearman's ρ = -0.19; P = 0.018). A small blood distribution area was the only risk factor for decreased FAH [odds ratio (OR) 8.43, confidence interval (CI) 95% (3.04-23.41); P < 0.001]. Binary logistic regression identified PI [OR 2.05, CI 95% (1.36-3.10); P = 0.001], FAH [OR 0.98, CI 95% (0.97-0.99); P = 0.005] and degree of stenosis [OR 0.95, CI 95% (0.92-0.99); P = 0.011] as risk factors for decreased flow after cardiopulmonary bypass (<30 ml/min). An increased PI (>3) was mainly influenced by percentage of flow change [OR 0.99, CI 95% (0.98-1.00); P = 0.031].

Conclusions: FAH and percentage of flow change are related to the dimensions of the target vessel and the degree of stenosis. The addition of flow measurements with the heart arrested provides additional information about the bypass graft, the quality of the anastomosis and the physiology of the coronary circulation.

Keywords: Coronary artery bypass grafting; Quality control; Transit-time flow measurement.

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Figures

Figure 1:
Figure 1:
Examples of intraoperative graft assessment. (A) Severe stenosis of the left main artery and a large distribution area. (B) Moderate stenosis of LAD and a large blood distribution area. (C) Severe stenosis of the LAD, small vessel with a small blood distribution area. CAG: coronary angiogram; LAD: left anterior descending artery; LIMA: left internal mammary artery; TTFM: transit-time flow measurement.
None
See this image and copyright information in PMC

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