The impact of competitive flow on distal coronary flow and on graft flow during coronary artery bypass surgery

Abstract

To determine the impact of left anterior descending-competitive flow (LAD-CF) on distal coronary flow (LAD-DF) and on left internal mammary artery-graft flow (LIMA-GF), we performed a quantitative blood-flow analysis in a swine model of a LIMA-to-LAD coronary artery bypass graft (CABG). In six swine, a LIMA-to-LAD CABG was performed. LAD blood-flow was measured bilaterally to the LIMA-to-LAD anastomosis, in the LIMA and in the pulmonary artery (cardiac output, CO) along with the LIMA pulsatility index (LIMA-PI) and the left ventricular pressure (LVP). PreCABG measurements were followed by postCABG measurements at five levels of LAD-CF: 100%, 75%, 50%, 25% and 0% after gradually snaring down a snare placed proximally of the LAD-CF flow-probe. PreCABG CO and LVP remained unchanged postCABG. LAD-DF was reduced significantly postCABG (-33%, P<0.0001). Reduction of the LAD-CF (at 75%, 50%, 25% and 0%) resulted in significant increase of LIMA-GF (+38%, +63%, +113%, +225%, P<0.036 at all LAD-CF levels), reduced PI (6.8, 5.7, 4.1, 3.1, 2.5) with simultaneous increase of LAD-DF (+8%, P=NS, +8%, P=NS, +17%, P=NS, +50%, P=0.0044). Decreased LAD-CF resulted in increased LAD-DF, increased LIMA-GF and decreased LIMA-PI. To the best of our knowledge, this is the first study where blood-flow was directly and simultaneously measured in all the components of the LIMA-to-LAD anastomosis.

Intraoperative transit time flow measurements during off‐pump coronary artery bypass surgery: The impact of coronary stenosis on competitive flow

“…Small canine and porcine studies showed a decrease in left internal mammary artery (LIMA) flow in patent coronary arteries. [10][11][12] Furthermore, a human study investigating the use of LIMA grafting in moderately stenotic coronary arteries 13 and one case report 14 showed similar results.…”

Free right internal mammary artery graft in bilateral internal mammary artery grafting

“…В случае некритического стеноза (≤70%) и, как следствие, наличия конкурентного кровотока результаты использования ВГА in situ снижаются до 77,8%. Некоторые авторы считают [18,19], что при наличии незначимого стеноза нативной артерии возникает конкурентный кровоток, который для маммарного кондуита, работающего по принципу потребности, приводит к редукции с последующей окклюзией. Подобная зависимость от нативного кровотока отсутствует при использовании ВГА свободным лоскутом.…”

Commentary: We are talking about a vessel and not just a pipe

“…In addition, biological signaling likely influences the LITA according to competitive flow and myocardium demands. 2 , 3 Gaudino and colleagues 7 have previously showed, in a series, that a high proportion of LITA grafts found to be malfunctioning at late angiography were due to technical issues, whereas functional LITA insufficiency only seemed to play a marginal role. It might be only in rare cases, ie, when the flow coming from the LITA is completely superfluous, that competitive flow leads to a permanently unfunctional graft.…”

“…Arterial grafts can dilate and therefore increase their flow in response to increased metabolic demands of the myocardium, or when the degree of stenosis in the coronary increases and vice versa ( Figure 1 ). 2 , 3

Figure 1 Illustration showing physiologic adaptation of the LITA according to varying degrees of stenosis in the coronary and to the metabolic myocardium demands. Arrow to the right shows that LITA can dilate and therefore increase its flow in response to increased metabolic demands of the myocardium, or when the degree of stenosis in the coronary increases.

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“…The 2 joined arteries, the LITA and its target revascularized coronary, interact together in supplying the myocardium. 2 Tsirikos Karapanos and colleagues 2 have showed experimentally that as the stenosis in the coronary increases or decreases, the blood flow through each artery compensates for the other. In addition, biological signaling likely influences the LITA according to competitive flow and myocardium demands.…”