Key result
Bypassing hemodynamically non-significant coronary lesions is linked to ~33% lower mean graft flow.
Why the study?
The study was conducted to assess the correlation between target coronary artery stenosis severity measured by iFR and intraoperative TTFM of attached grafts, and to evaluate flow competition.
Does preoperative instantaneous wave-free ratio (iFR) predict intraoperative graft flow and competitive flow in patients undergoing CABG?
Observational (n=25)
No
Does preoperative instantaneous wave-free ratio (iFR) predict intraoperative graft flow and competitive flow in patients undergoing CABG?
Absolute Event Rate: 31.3% vs 46.9%
p-value: p=0.002
Preoperative iFR assessment can predict competitive flow in CABG grafts, demonstrating that grafting vessels with non-significant stenosis (iFR > 0.90) leads to poorer graft flow parameters.
Background and Objectives: To assess the correlation between the degree of target coronary artery stenosis measured by instantaneous wave-free ratio (iFR) and the intraoperative transit time flow measurement (TTFM) of attached grafts as well as evaluate flow competition between the native coronary artery and the attached graft according to the severity of stenosis. Materials and Methods: In total, 89 grafts were subjected to intraoperative transit time flow measurement after coronary artery bypass grafting (CABG) in 25 patients with multivessel coronary artery disease (CAD). The iFR was evaluated for all coronary arteries with grafts. The coronary artery stenoses were divided into three groups based on the iFR value: iFR < 0.86 (group 1); iFR 0.86–0.90 (group 2); and iFR > 0.90 (group 3). Results: The mean graft flow (MGF) was 46.9 ± 18.4 mL/min for group 1, 45.3 ± 20.9 mL/min for group 2, and 31.3 ± 18.5 mL/min for group 3. A statistically significant difference was confirmed between groups 1 and 3 (p = 0.002) and between groups 2 and 3 (p = 0.025). The pulsatility index (PI) was 2.49 ± 1.20 for group 1, 2.66 ± 2.13 for group 2, and 4.70 ± 3.66 for group 3. A statistically significant difference was found between groups 1 and 3 (p = 0.006) and between groups 2 and 3 (p = 0.032). Backward flow was detected in 7.5% of grafts for group 1, in 16.6% of grafts for group 2, and in 16% of grafts for group 3. A statistically significant difference was found between groups 1 and 2 (p = 0.025) and between groups 1 and 3 (p = 0.029). Conclusions: The iFR is a useful tool for predicting the impact of competitive flow observed between a native artery and an attached graft. The effect of competitive flow significantly increases when the graft is attached to a vessel with mild coronary stenosis. In a coronary artery where the iFR was not hemodynamically significant, the MGF was lower, the PI was higher, and a larger proportion of grafts with backward flow (BF) was detected compared to when there was significant stenosis (iFR < 0.86).
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Tolegenuly et al. (2020) conducted an observational in Multivessel stable coronary artery disease (n=25). Hemodynamically non-significant coronary stenosis (iFR > 0.90) vs. Severe coronary stenosis (iFR < 0.86) was evaluated on Mean graft flow (MGF) in mL/min (p=0.002). Grafts attached to coronary arteries with hemodynamically non-significant stenosis (iFR > 0.90) demonstrated significantly lower mean graft flow compared to those with severe stenosis (31.3 vs 46.9 mL/min, p=0.002).
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