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CAN LAD OCCLUSION RESTORE LIMA GRAFT FLOW?
Running Title: Competetive Flow Between LAD and LIMA
Assist. Prof. M. Hakan Tas, M.D.1, Assist. Prof. Ziya Simsek, M.D.1, Dr.Husnu Degirmenci,
M.D.1, Assist. Dr. Lutfu Askin , M.D.1, Assoc. Prof. Ednan Bayram, M.D1, Prof. Huseyin Senocak,
M.D 1 .
1
Department of Cardiology, Faculty of Medicine, Ataturk University, Erzurum, Turkey
Address for correspondence:
Assist.Prof.Dr.M. Hakan Tas
Atatürk University Cardiology Department
25240-Erzurum/TURKEY
Telephone: +90-532-6856848
Fax number: +904422352384
E-mail: mhakantas@gmail.com
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Abstract
Competetive flow is the major reason for failure of Coronary Artery Bypass Grafting
(CABG). Physiological effects and etiological causes of coronary competetive flow are still
certainly unknown. But in noncritical coronary lesions it is more frequently and on higher
rates. For this reason if you are deciding for CABG it is important to evaluate coronary
lesions correctly for prevention of coronary competetive flow. This case report introduces
clinically improved coronary arterial disease after turning of competetive flow to graft artery
by worsening stenosis of native coronary artery.
Keywords: Angiography, Competetive flow, Coronary Artery Bypass Grafting.
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Introduction
Competetive flow is defined as competetion of native arteries and grafts for distal
perfusion after Coronary Artery Bypass Grafting ( CABG ) operation. 1 Cause of this
phenomenon is certanly unknown however it is affected by the degree of stenosis on diseased
vessel, kind of the graft, diameter of graft vessel and anastomosed diseased vessel, injury of
graft and technical inaccuracies .2 In this report we want to acquire a case for literature which
is clinically improved coronary arterial disease after turning of competetive flow to graft
artery by worsening the stenosis of native coronary artery.
Case
63 years old male applied to our policlinic with typical chest pain. In his medical
history after an inferior myocardial infarction and a stent was implanted to right coronary
artery (RCA) 2 years ago. 1 years ago patient underwent surgical revascularisation involving
left internal mammarian artery (LIMA) graft on left anterior descending artery (LAD) and a
venous graft on RCA. Patient has got diabetes mellitus and hypertension. We found
pathologic Q vawes on ECG. Cardiac markers were normal. Patient admitted to our
cardiology clinic. Despite medications patient’s chest pain continued. Patient has undergone
coronary angiography. Native RCA was 90% stenosed but venous graft was patent. 70%
stenosis in proximal LAD on cranial position founded. There was no flow in LIMA graft
(Figure 1A). A stent was implanted to LAD and TIMI 3 flow restored (Figure 1B). Patient
discharged from hospital with medications. Five months later patient applied to our policlinic
with exercise induced angina. We learned that patient did not take his drugs regularly. And a
new coronary angiography performed. 90% instent restenosis founded in LAD (Figure 1C).
But LIMA-LAD bypass was seen patent (Figure 2A-B). We thought that current situation
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originated from the competetive flow between LIMA graft and native LAD. Patient’s medical
treatment arrenged again and discharged from the hospital.
Discussion
The main cause for insufficiency of coronary bypass grafts is the competetive flow
with native coronary arteries. Contributary factors for competetive flow are progression of
atherosclerosis, intimal hyperplasia and technical deficiencies.3 However noncritical coronary
arterial stenosis decreases wall shear stress of LIMA graft and anastomosis; in this wise
competetive flow increases. Nowadays computational liquid dynamics is used for
investigating the wall shear stress of bypass graft and native coronary arteries.4
Some studies showed relationship between stenosis of native coronary artery and the
degree of competetive flow. Berger et al. reported that proximal coronary arterial stenosis is
the major indicator of the LIMA graft occlusion.5 Pevni et al. reported that noncritical
coronary arterial stenosis causes nonfunctioning grafts.6 Nordgaard et al. showed that high
grade competetive flows could be originate from noncritical coronary lesions and partial
competetive flows could be originate from critical coronary lesions. They did not see
competetive flow in totally stenosed coronary arteries.2 A recently published animal study
showed the predictive value for competetive flow of LIMA graft is the <75% stenosis of
coronary arteries.7 In our case we thought that high grade competetive flow occured by the
mistake of evaluating coronary lesions before bypass operation. In the light of existing studies
we observed that the noncritical coronary lesions contribute competetive flow. Siebenmann et
al. reported string phenomenon of the internal mammarian artery caused by 50% and less
stenosis of grafted vessel.8 In our case we did not see string phenomenon because of
competetive flow. This event can be attached to not enough time for development of
endotelial dysfunction and partial competetive flow. Our case is instructive and remarkable
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for bypass grafted noncritical lesions can cause competetive flow and it can worsen coronary
arterial disease clinically. But our patient's coronary arterial disease improved and changed
the flow LAD to LIMA.
Conclusion:
Decision for CABG should be given with multidisciplinary approach and competetive
flow should always be considered. However, diameter mismatch of graft and artery and
bypass grafting to mild lesions should be avoided. On controversial cases measuring flows of
two vessels can be directive for avoiding competetive flow.
References
1. Pagni S, Storey J, Ballen j, et al. Factors affecting internal mammary artery graft
survival: how is competitive flow from a patent native coronary vessel a risk factor? J
Surg Res 1997; 71(2):172-178.
2. Nordgaard H, Nordhaug D, Kirkeby-Garstad, Lovstakken L, Vitale N, Haaverstad R.
Different graft flow patterns due to competitive flow or stenosis in the coronary
anastomosis assessed by transit-time flowmetry in a porcine model. Eur J
Cardiothorac Surg. 2009; 36(1): 137-142.
3. Nwasokwa ON. Coronary artery bypass graft disease. Ann Intern Med 1995;123: 528
– 533.
4. Stone PH, Coskun AU, Kinlay S, Popma JJ, Sonka M, Wahle A et al . Regions of low
endothelial shear stress are the sites where coronary plaque progresses and vascular
remodelling occurs in humans: an in vivo serial study. Eur Heart J 2007;28:705 – 710.
5. Berger A, MacCarthy PA, Siebert U, Carlier S, Wijns W, Heyndrickx G et al. Longterm patency of internal mammary artery bypass grafts: relationship with preoperative severity of the native coronary artery stenosis. Circulation 2004;110:11-36.
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6. D. Pevni, I. Hertz, B. Medalion et al.’Angiographic evidence for reduced graft patency
due to competitive flow in composite arterial grafts’’. The Journal of Thoracic and
Cardiovascular Surgery. vol. 133, no. 5, pp. 1220–1225, 2007.
7. Havard N, Abigail S, Dag N, et al. Impact of competitive flow on wall shear stress in
coronary surgery: computational fluid dynamics
of a LIMA-LAD model.
Cardiovascular Research (2010) 88, 512-519.
8. Siebenmann R, Egloff L, Hirzel H, Rothlin M, Studer M, Tartini R. The internal
mammary artery string phenomenon. Analysis of 10 cases. Eur J Cardiothorac Surg.
1993; 7(5):235-8.
Figure Legends
Figure 1A: The angiographic view at the anterior-posterior position; there was no flow from
LIMA graft to LAD. 1B: The angiographic view at the left caudal oblique position; there was
TIMI 3 flow in LAD after stent implantation.1C: The angiographic view at the left caudal
oblique position; there was a critical lesion in proximal LAD after stent restenosis.
Figure 2A-B
The angiographic views at the anterior-posterior position; LIMA graft flow restored after
LAD occlusion
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Figure 1A-B-C
Figure 2A-B