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SECTION 6 Conduits forcoronary artery bypass graft surgery228

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gra biology (Fig. 27.3). Reactive oxygen species production in vein gra wall diminishes nitric oxide (NO) availability by directly reacting with NO and also by causing endothelial NO synthase uncoupling and reduced NO production. Endothelial dysfunction, and expression of adhesion cell molecules favours gra thrombosis and occlusion. Assessment of peripheral endothelial function by non- invasive means (e.g. ow- mediated dilation of brachial artery) poorly correlates with SVG biology. Nonetheless vasomotor organ bath studies in vein gras suggest that impaired ex vivo vasorelaxation of SVG to acetylcholine is associated with reduced early vein patency.

Graft de- endothelization

Graft de- endothelization as a result of surgical manipulation of the vein impairs graft endothelial function, and favours platelet activation and graft thrombosis. Mechanical endothelial

denudation due to harvesting, and exposure of extracellular matrix proteins and tissue factor to the lumen tissue can also result in platelet activation. Activated platelets express thrombogenic substances (e.g. platelet- derived growth- factor (PDGF), transforming growth factor- beta (TGF- β)), and adhesion molecules (e.g. P- selectin, E- selectin, platelet endothelial cell adhesion molecule- 1 (PECAM- 1)), that promote the infiltration of graft wall by immune cells. The interplay between endothelial dysfunction, inflammation, vasoconstriction, and prothrombotic signalling favours graft occlusive thrombosis. This early period of increased thrombotic risk after engraftment is overcome by the adaptation of the vein to arterial conditions and its reendothelization. The latter is a process which starts during the first week post engraftment via the mobilization of endothelial progenitor cells restoring endothelial health and endothelial NO synthase function.

Fig.27.2 Pathophysiology of early and late graft failure. Different biological mechanisms contribute to the pathophysiology of vascular graft

failure. Although early failure is linked to technical factors resulting in endothelial injury and activation with subsequent thrombosis, late failure is more commonly the result of atherogenesis and plaque rupture. In the early stages after graft implantation, endothelial injury because of surgical manipulations and endothelial cell activation (e.g. because of haemodynamic stress or transient ischaemia) can result in the release of prothrombotic and proinﬂammatory molecules (e.g. von Willebrand factor, CD40L, tissue factor) that trigger the thrombotic cascade resulting in acute occlusion. Impaired endothelial function (characterized by poor nitric oxide bioavailability) also promotes a proinﬂammatory and prothrombotic phenotype, whereas local release of cytokines such as PDGF promotes cell migration and neointima formation. On the contrary, late failure (months to years after surgery) is associated with atherosclerotic vascular disease. Systemic biological factors (e.g. diabetes mellitus, smoking, hypercholesterolaemia) and local biological mechanisms (e.g. increased oxidative stress, vascular inﬂammation, endothelial dysfunction) all contribute to the initial plaque formation and subsequent progression until the ﬁnal stage of plaque rupture resulting in thrombosis and occlusion to blood ﬂow. CD40L, cluster of differentiation 40 ligand; LDL, low- density lipoprotein; NO, nitric oxide; PAI- 1, plasminogen activator inhibitor 1; PDGF, platelet- derived growth factor; ROS, reactive oxygen species; TXA2, thromboxane A2; VCAM- 1, vascular cell adhesion molecule 1; VSMC, vascular smooth muscle cell; and vWF, von Willebrand factor.

Reproduced from Gaudino, M., Antoniades, C., Benedetto, U., Deb, S., Di Franco, A., Di Giammarco, G., Fremes, S., Glineur, D., Grau, J., He, G.W., Marinelli, D., Ohmes, L.B., Patrono, C., Puskas, J., Tranbaugh, R., Girardi, L.N., Taggart, D.P. & Alliance, A.2017. Mechanisms, Consequences, and Prevention of Coronary Graft Failure. Circulation, 136, 1749– 1764 with permission from Wolters Kluwer.

27 Early vein graftfailure 229

No Atorvastatin

+SOD

Atorvastatin 5μM Atorvastatin 50μM

)(

https://t.me/medicina_free

(a) (c) (e)

Effects ofsurgery

Early gra failure is traditionally attributed to technical factors associated with the surgical technique, the quality of anastomoses, and gra– target vessel size mismatch. Competitive ow from native coronary arteries without critical stenosis can also result in poor gra ow and early gra occlusion. Proinammatory and prothrombotic mechanisms activated by CABG surgery may also play a role in acute gra thrombosis in the early postoperative period. For example, the use

(b) (d) (f)

of cardiopulmonary bypass surfaces and aortic cross- clamping leads to platelet retention and dysfunction, and thrombin- mediated procoagulant eects; a transient hypercoagulable and proinammatory state is seen with both on- and o- pump techniques.

Intimalhyperplasia

Following the risk of acute thrombosis early postoperatively, intimal

Fig.27.3 Production of superoxide radicals from vein vascular wall and

the direct effects of statins. Vascular segments of saphenous vein grafts (SVGs) were incubated ex vivo with atorvastatin 0 μmol/ L (a, b), 5 μmol/ L (c, d), or 50 μmol/ L (e, f) in the presence (b, d, and f ) and absence (a, c, and e) of PEG- conjugated superoxide dismutase (SOD) (500 U/ mL). SOD inhibited dihydroethidium staining. Superoxide (O

−

) generation (red)

from both the vascular wall and vascular endothelium (arrowheads) was reduced after incubation with atorvastatin compared to control (ﬁgure shows representative example).

Reproduced from Antoniades, C., Bakogiannis, C., Tousoulis, D., Reilly, S., Zhang, M.H., Paschalis, A., Antonopoulos, A., Demosthenous, M., Miliou, A ., Psarros, C., Marinou, K., Sfyras, N., Economopoulos, G., Casadei, B., Channon, K.M. & Stefanadis, C.2010. Preoperative Atorvastatin Treatment in CABG Patients Rapidly Improves Vein Graft Redox State by Inhibition of Rac1 and NADPH- Oxidase Activity Preoperative Atorvastatin Treatment in CABG Patients Rapidly Improves Vein. Circulation, 122, S66– 73 with permission from Wolters Kluwer.

hyperplasia of the gra may develop in the rst year post CABG. Histologically, intimal hyperplasia is the result of proliferation and migration of vascular smooth muscle cells from the media into the intima and subsequent intimal expansion via production of broblastic factors (e.g. TGF- β and PDGF). Engrament of SVG in the arterial circulation leads to increased ow and circumferential wall shear stress which can lead to vascular wall damage and inltration of platelets, brin, and leucocytes (Fig. 27.4). Ischaemia– reperfusion injury of smooth muscle cells during harvesting may also result in smooth muscle cell activation and migration to the intima. Adventitial broblasts also contribute to intimal hyperplasia formation in vein gras, which do not have an elastic laminae, and therefore adventitial broblasts can unrestrictedly migrate to the

(a)

100 μm100 μm

(e)(d)

250 μm

200 μm

250 μm

Fig.27.4 Immunohistochemical characterization of vein grafts. Representative examples of immunohistochemistry studies of murine vein grafts.

(a)Staining for macrophage (brown) and smooth muscle cell (blue) showing heterogeneous areas highly positive for both cell types. (b)CD31- stained endothelial cells (red) highlight neovessels in an advanced atherosclerotic vein graft lesion. (c)Fibrin deposition (brown) in an early (14- day- old) vein graft section. (d, e) Immunoﬂuorescent double staining of CD31 positive neovessels (red) and erythrocytes (green) showing a lesion with intact matured neovessels. All erythrocytes are within the neovessels (d)and a lesion with leaky neovessels displaying intraplaque haemorrhage. Erythrocytes are found throughout the lesion and are not restricted by the neovessels (e).

Source data from de Vries, M.R., Simons, K.H., Jukema, J.W., Braun, J.& Quax, P.H. A.2016. Vein graft failure:from pathophysiology to clinical outcomes. Nature Reviews Cardiology, 13, 451.

SECTION 6 Conduits forcoronary artery bypass graft surgery230

Sabik JF, et al. Ann Thorac Surg 2005

Song SW, et al. Korean Circ J 2012

Occlusion

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On pump

Off pump

On/Off pump

Overall

SVG occlusion (% of grafts)

13612

SVGs (n)

(%)

13,944

8.1±0.9%

Time post CABG (months)

1,165

12.4±2.3%

15.0±3.0%

1,482

33,446

18.6±1.4%

Mehta RH, et al. Circulation 2011 Nakano J, et al. J Thorac Cardiovasc Surg 2013 Fitzgibbon GM, et al. J Am Coll Cardiol 1996 Hattler B, et al. Circulation 2012 Ohira S, et al. Heart Lung Circ 2016 Raza S, et al. J Am Coll Cardiol 2017 Fukui T, et al. Ann Thorac Surg 2010 Tan ES, et al. J Am Coll Cardiol 1999 Sanz G, et al. Circulation 1990 Wu H, et al. Ann Thorac Surg 2015 Desai ND, et al. N EnglJ Med 2004 Goldman S, et al. Circulation 1989 Kim YH, et al. Ann Thorac Surg 2017 Goldman S, et al. JAMA 2011 McLean RC, et al. J Cardiovasc Surg (Torino) 2011 Widimsky P, et al. Circulation 2004 Kim KB, et al. J Thorac Cardiovasc Surg 2008 Gao C, et al. Interact Cardiovasc Thorac Surg 2009 Gao G, et al. J Am Coll Cardiol 2010 Tanaka A, et al. Heart Vessels 2016 Puskas JD, et al. JAMA 2004 Oshima H, et al. Interact Cardiovasc Thorac Surg 201 Goldman S, et al. Circulation 1991 Chesebro JH, et al. N EnglJ Med 1982 Campeau L, et al. Circulation 1975 Kobayashi J, et al. Circulation 2005 Noiseux N, et al. J Thorac Imaging 2017 Al-RuzzehS, et al. BMJ 2006 Sousa UvaM, et al. Eur Heart J 2010 Mannacio VA, et al. Heart 2012 Yun KL, et al. J Thorac Cardiovasc Surg 2005 Campbell PG, et al. Br J Radiol 2009 Gavaghan TP, et al. Circulation 1991 Yamane Y, et al. Gen Thorac Cardiovasc Surg 2017 Lingaas PS, et al. Ann Thorac Surg 2006 Kulik A, et al. Circulation 2010 Cho KR, et al. Eur J Cardiothorac Surg 2006 Bassri H, et al. BMC Cardiovasc Disord 2009 Khan NE, et al. N Engl J Med 2004 Brown BG, et al. Circulation 1985 Sun JC, et al. Am Heart J 2010 Arampatzis CA, et al. EuroIntervention 2016 Nathoe HM, et al. N Engl J Med 2003 Gummert JF, et al. Ann Thorac Surg 2006 Yoo KJ, et al. Eur J Cardiothorac Surg 2003 Perrault LP, et al. J Thorac Cardiovasc Surg 2004

Fig.27.5 Published studies and reported rates of early saphenous vein graft (SVG) occlusion. The ﬁgure shows the rates of early SVG occlusion

≤12months after coronary artery bypass grafting (CABG) from a total of 48 published studies on 23,103 patients, involving follow up of 41,530 SVGs. The size of each study on the graph is weighted for its sample size. The number of each study on the graph corresponds to the reference number of each study.

intima. Bone marrow- derived progenitor cells are also reportedly involved in vein gra intimal hyperplasia. Expression of growth factors (e.g. vascular endothelial growth factor, basic broblastic

to native coronary artery disease, which may rapidly progress. Atherosclerotic lesions in SVGs are also more prone to rupture and

total vessel occlusion with a high thrombotic burden. growth factor, TGF-β), and extracellular matrix degradation by matrix metalloproteinases (MMP), mainly MMP- 2 and MMP- 9, by activated smooth muscle cells or broblasts are the pivotal underlying mechanisms of intimal hyperplasia development. Overexpression of

Incidence and clinical predictors ofearly vein graftfailure

tissue inhibitors of MMPs (TIMPs) attenuates intimal hyperplasia formation in animal models. Gra intimal hyperplasia is typically seen at the anastomotic sites within the rst months post CABG, but it can also be generalized and result in critical stenosis and poor gra ow. Low or high shear stress and/ or a mismatch in the elastic properties of vascular gras and native vessels have been also implicated in the mechanisms of intimal hyperplasia.

Graftatherosclerosis

Vein gra failure due to atherosclerosis is typically seen late aer surgery. Development of foam cells in human SVGs can be observed from as early as the rst year, while a necrotic core, neovessel formation, and intraplaque haemorrhage are typically developed aer the second year post CABG (Fig. 27.4). Atherosclerosis of SVGs is characterized by a more diuse and concentric pattern compared

ere are reports of reduced gra patency at 12– 18months with

the use of endoscopic vein harvesting. is has been tradition-

ally attributed to the better preservation of gra biology with open

vein harvesting, although results from recent randomized trials

failed to detect any signicant dierences between open and endo-

scopic vein harvesting in terms of gra biology and mid- term clin-

ical outcomes., In the Radial Artery Patency Study, diabetes

mellitus was an independent predictor of gra occlusion at 1year

post- CABG (relative risk 1.45, 95% condence interval 1.03– 2.05;

P=0.03). Other factors that have been associated with increased

risk of SVG failure within the rst year post CABG are female sex,

small target vessel size, or o- pump surgery. Biological factors,

such as vascular oxidative stress and gra endothelial function,

could be equally important in the development of SVG disease,

27 Early vein graftfailure 231

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but their predictive role has not been explored to date. us, in contrast to the long- term patency of SVGs which has been systematically investigated in several clinical studies, the risk factors for early SVG occlusion are less well understood. Surprisingly there is a large discrepancy in the reported rates of SVG occlusion early post CABG, which even in the more recent studies ranges from 4% to as high as 46% at 12months. An overview of the incidence of SVG occlusion within the rst postoperative year is provided in Fig. 27.5 (data from a total of 48 clinical studies and 41,530 SVGs).

e risk factors for late gra occlusion are not dierent from the classic atherosclerotic ones. In one of the largest studies with long- term angiographic follow- up of 11,519 CABG patients, internal thoracic artery gra patency was stable over time at 1, 5, 10, and 20years, 96%, 96%, 95%, and 93%, while SVG patency was estimated at 82%, 72%, 58%, and 41% respectively at the same time points. Female sex, triglycerides, and le circumex graing were all independent risk factors for gra occlusion. Surprisingly, in this study diabetes mellitus was not an independent predictor of late gra failure. Conversely, other studies support a detrimental eect of diabetes on late gra patency. e impact of traditional atherosclerotic risk factors on gra patency increases late (i.e. years) aer surgery. In a study that involved long- term angiographic follow- up of gras (i.e. >10years aer surgery), age, cholesterol levels, and Canadian functional class II– IV were independent predictors of long- term gra status.

With regard to the prevention of gra failure, the introduction of single antiplatelet therapy decades ago was associated with improved gra patency in relevant landmark clinical trials. Recently, the use of dual antiplatelet treatment using ticagrelor plus aspirin was found to signicantly increase gra patency aer 1year compared to aspirin alone. Notably, there is evidence that nonselective administration of dual antiplatelet therapy to all CABG patients increases bleeding risk. Intraoperative gra ow measurements are important to identify gra malfunction, but they lack standardization to reliably guide interventions. Increasing perivascular delivery of NO seems a promising strategy to preserve vein endothelial function and possibly also gra patency too. Statins have benecial pleiotropic vascular eects, including endothelial function improvement, reduction of vascular oxidative stress and inammation, and could potentially prevent gra failure. We have previously shown that ex vivo incubation of SVGs with statins leads to a rapid decrease in superoxide generation. Ongoing trials aim at exploring whether high- dose statin treatment may reduce vein gra failure.

Conclusion

e mechanisms of gra failure are complex, and involve patientrelated clinical risk factors, operation- related technical factors, such as the quality of anastomoses, gra size, and target vessel size, and stenosis as well as gra biology. Preventive treatments to reduce acute gra thrombosis and intimal hyperplasia (e.g. with dual antiplatelet therapy or high- dose statins respectively), may have a role in the prevention of gra failure but further evidence is required to select the most appropriate patients for such interventions.

REFERENCES

1. Motwani JG, Topol EJ. Aortocoronary saphenous vein gra disease:pathogenesis, predisposition, and prevention. Circulation. 1998;97(9):916– 31.

2. Raza S, Blackstone EH, Houghtaling PL, Rajeswaran J, Riaz H, Bakaeen FG, etal. Inuence of diabetes on long- term coronary artery bypass gra patency. J Am Coll Cardiol. 2017;70(5):515– 24.

3. Gaudino M, Antoniades C, Benedetto U, Deb S, Di Franco A, Di Giammarco G, etal. Mechanisms, consequences, and prevention of coronary gra failure. Circulation. 2017;136(18):1749– 64.

4. De Vries MR, Simons KH, Jukema JW, Braun J, Quax PHA. Vein gra failure:from pathophysiology to clinical outcomes. Nat Rev Cardiol. 2016;13(8):451– 70.

5. Antoniades C, Bakogiannis C, Tousoulis D, Reilly S, Zhang MH, Paschalis A, etal. Preoperative atorvastatin treatment in CABG patients rapidly improves vein gra redox state by inhibition of Rac1 and NADPH- oxidase activity. Circulation. 2010;122(11 Suppl):S66– 73.

6. Antoniades C, Mussa S, Shirodaria C, Lee J, Diesch J, Taggart DP, etal. Relation of preoperative radial artery ow- mediated dilatation to nitric oxide bioavailability in radial artery gras used in o- pump coronary artery bypass graing. Am J Cardiol. 2009;103(2):216– 20.

7. Antonopoulos AS, Odutayo A, Oikonomou EK, Trivella M, Petrou M, Collins GS, Antoniades C; SAFINOUS-CABG (Saphenous Vein Gra Failure—An Outcomes Study in Coronary Artery Bypass Graing) group. Development of a risk score for early saphenous vein gra failure: An individual patient data meta-analysis. J orac Cardiovasc Surg. 2020 Jul;160(1):116–

127.e4. doi: 10.1016/j.jtcvs.2019.07.086.

8. Antonopoulos AS, Kardos A, Antoniades C. Reply from authors: Vein gra biology and the risk of gra occlusion. J orac Cardiovasc Surg. 2020 Jul;160(1):e2–e4. doi: 10.1016/j. jtcvs.2020.04.048. Epub 2020 May 21.

9. Biglioli P, Cannata A, Alamanni F, Naliato M, Porqueddu M, Zanobini M, etal. Biological eects of o- pump vs. on- pump coronary artery surgery:focus on inammation, hemostasis and oxidative stress. Eur J Cardiothorac Surg. 2003;24(2):260– 69.

10. Van Straten AHM, Soliman Hamad MA, Van Zundert AJ, Martens EJ, Schönberger JPAM, De Wolf AM. Preoperative Creactive protein levels to predict early and late mortalities aer coronary artery bypass surgery:eight years of follow- up. J orac Cardiovasc Surg. 2009;138(4):954– 58.

11. Lemson MS, Tordoir JH, Daemen MJ, Kitslaar PJ. Intimal hyperplasia in vascular gras. Eur J Vasc Endovasc Surg. 2000;19(4):336– 50.

12. George SJ, Johnson JL, Angelini GD, Newby AC, Baker AH. Adenovirus- mediated gene transfer of the human TIMP- 1 gene inhibits smooth muscle cell migration and neointimal formation in human saphenous vein. Hum Gene er. 1998;9(6):867– 77.

13. Lopes RD, Haey GE, Allen KB, Ferguson TB, Peterson ED, Harrington RA, etal. Endoscopic versus open vein- gra harvesting in coronary- artery bypass surgery. N Engl J Med. 2009;361(3):235– 44.

14. Krishnamoorthy B, Critchley WR, ompson AJ, Payne K, Morris J, Venkateswaran RV, etal. Study comparing vein integrity and clinical outcomes in open vein harvesting and 2 types of endoscopic vein harvesting for coronary artery bypass graing:the VICO randomized clinical trial (vein integrity and clinical outcomes). Circulation. 2017;136(18):1688– 702.

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15. Zenati MA, Bhatt DL, Bakaeen FG, Stock EM, Biswas K, Gaziano JM, etal. Randomized trial of endoscopic or open vein- gra harvesting for coronary- artery bypass. N Engl J Med. 2019;380(2):132– 41.

16. Desai ND, Cohen EA, Naylor CD, Fremes SE, Radial Artery Patency Study Investigators. Arandomized comparison of radialartery and saphenous- vein coronary bypass gras. N Engl J Med. 2004;351(22):2302– 9.

17. Mclean RC, Nazarian SM, Gluckman TJ, Schulman SP, iemann DR, Shapiro EP, etal. Relative importance of patient, procedural and anatomic risk factors for early vein gra thrombosis aer coronary artery bypass gra surgery. J Cardiovasc Surg (Torino). 2011;52(6):877– 85.

18. Dashwood MR, Tsui JC. ‘No- touch’ saphenous vein harvesting improves gra performance in patients undergoing coronary artery bypass surgery:a journey from bedside to bench. Vascul Pharmacol. 2013;58(3):240– 50.

19. Widimsky P, Straka Z, Stros P, Jirasek K, Dvorak J, Votava J, etal. One- year coronary bypass gra patency:a randomized comparison between o- pump and on- pump surgery angiographic results of the PRAGUE- 4 trial. Circulation. 2004;110(22):3418– 23.

20. Zhao Q, Zhu Y, Xu Z, Cheng Z, Mei J, Chen X, Wang X. Eect of ticagrelor plus aspirin, ticagrelor alone, or aspirin alone on saphenous vein gra patency 1year aer coronary artery bypass graing:a randomized clinical trial. JAMA. 2018;319(16):1677– 86.

21. Margaritis M, Channon KM, Antoniades C. Statins and vein gra failure in coronary bypass surgery. Curr Opin Pharmacol. 2012;12(2):172– 80.

22. Kulik A, Abreu AM, Boronat V, Ruel M. Intensive versus moderate atorvastatin therapy and one- year gra patency aer CABG:rationale and design of the ACTIVE (Aggressive cholesterol erapy to Inhibit Vein Gra Events) randomized controlled trial (NCT01528709). Contemp Clin Trials. 2017;59:98– 104.

Surgeon’s experienc

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The selection ofconduits forcoronary artery bypasssurgery

Mario Gaudino, Martin Misfeld, and R. John. L. Brereton

Introduction

Coronary artery bypass graing (CABG) is the most common adult cardiac surgery operation performed in the United States and probably worldwide. Complete revascularization and excellent patency of the implanted gras are the primary aims of CABG; individualized selection of conduits appropriate for the specic coronary anatomy and clinical characteristics of each patient is key to achieving this goal.

e preoperative planning phase of the graing strategy is arguably one of the most important parts of the CABG operation and includes a careful review of the precise coronary anatomy, the size and quality of the proposed target vessels, the quality and severity of the stenosis, the proposed conguration of gra deployment, evaluation of the availability of the various CABG conduits, and a detailed assessment of patient comorbidities and functional status that may aect gra harvest. e operator’s experience and familiarity with the various alternative graing congurations may also play a role in the decision- making process. e specic preoperative tests aimed at assessing the suitability of various conduits are detailed in the chapters dedicated to the radial artery (RA), the internal thoracic arteries (ITAs), and the gastroepiploic artery. Mapping of the saphenous vein (SV) may be potentially useful and is increasingly used in clinical practice.

Of note, despite the relatively long history of CABG, limited evidence and very few specic guidelines currently exist on the choice of conduits for CABG. One notable exception is the Society of oracic Surgeons clinical practice guidelines on arterial conduits for coronary artery bypass graing that will be extensively quoted in this chapter. Fiy years aer Favaloro’s systematic description of CABG, the choice of conduits remains as much art as science.

The right internal thoracicartery

gra. Large angiographic datasets have shown extremely high patency rates at very long- term follow- up (>90% at 15years) and a large body of observational evidence suggests longer survival for patients receiving multiple ITA gras.– 

Technically, the use of the right ITA is probably more challenging than that of the RA because of its more fragile wall and more limited length that requires careful intraoperative judgement of the gra geometry. For surgeons with limited experience with arterial gras, the RA should probably be the rst step to provide patients with a second arterial conduit, and the right ITA may be better reserved for a more advanced phase of the arterial graing learning curve. is is especially true in cases where complex graing strategies (Y gras, sequentials) are planned (Fig. 28.1).

Most frequently, the right ITA is used in situ to gra the le anterior descending artery, or as a free composite gra anastomosed to the le ITA when its length is inadequate to reach the le anterior descending artery, or if more than two distal anastomoses are required on the le side.

e use of the right ITA to the right coronary artery has been associated with suboptimal patency rates unless the stenosis of the native right coronary artery is severe. Nonetheless, some authors routinely use ITA Y gras with the last anastomosis to the posterolateral branch of the right coronary artery with good results. Compared

RITA

Grafting complexity

–

RITA

Due to the widely accepted prognostic importance of the use of the le ITA to revascularize the le anterior descending artery, the right ITA has traditionally been considered the natural second arterial

Fig.28.1 Individualization of the second arterial conduit to the grafting

strategy and the operator experience. RA, radial artery; RITA, right internal thoracic artery.

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Table28.1 Scheme forthe choice ofthe second arterial conduit.

RA RITA

High risk of mediastinitis + –

Moderate target vessel stenosis – +

Distal or multiple targets + –

Lack of ulnar compensation or previous transradial procedure

RA, radial artery; RITA, right internal thoracic artery.

– +

availability of fractional ow reserve or other functional data is ideal to inform decision- making in this setting).

e RA is particularly indicated as the second arterial gra in patients for whom the use of bilateral ITAs is likely to signicantly increase the risk of sternal wound complications. Apost- hoc analysis of the Radial Artery Patency Study reported excellent results of the RA in patients with diabetes, making the use of this conduit in this population particularly attractive, due to the increased risk of sternal complications when both ITAs are used.

e most important contraindication to the use of the RA is the lack of adequate perfusion across the palmar arch from the ulnar

to the RA, the ITA is less sensitive to competitive ow and is a better solution when used to gra target vessels with moderate stenosis.

e right ITA can be anastomosed to the ascending aorta with good mid- term patency, although many surgeons prefer to suture a very short piece of vein to the ascending aorta and anastomose the free right ITA to that vein hood, avoiding a direct anastomosis between the relatively thick- walled aorta and the thin- walled, small- calibre, fragile

artery. e incidence of this nding varies based on the methods of detection and denition used, but there is a small number of patients whose hand circulation is RA dependent— see Chapter35 on the RA for details. Reynaud’s disease, chronic renal failure, and collagen vascular diseases are other important contraindications to RA harvesting. RAs used for transradial coronary procedures should not be used for CABG, unless no other conduit is available.

right ITA. is conguration may allow the extra length required to gra more distal targets when a Y gra composite conduit taking inow from the le ITA cannot be used. Asimple scheme for the choice

The gastroepiploicartery

between the RA and the right ITA is provided in Table 28.1.

e most important downside to the use of bilateral ITAs is the increased risk of sternal wound complications. is risk can be signicantly reduced (but probably not abolished, at least in high- risk patients) by using the skeletonization technique for harvesting. Specic details are given in the relevant chapters on bilateral ITAs and skeletonization harvesting techniques.

e gastroepiploic artery (see Chapter36) is widely used in Asia, and, despite some reluctance from the Western surgical community, is an excellent choice to gra the posterior wall. Adetailed description of the indications for its use and relevant technical considerations is given in the dedicated chapter. It is important that the target vessel has a severe stenosis and that the artery is harvested using the atraumatic skeletonized method. e gastroepiploic artery can be

The radialartery

used to substitute the RA in the right coronary system when the RA is not available, or as a third arterial gra to complete a total arterial revascularization strategy.

e RA is the second arterial conduit for which the most solid evidence exists to date. In fact, with the exception of the use of the ITA to gra the le anterior descending artery, the use of the RA is the only classIrec-

The saphenousvein

ommendation regarding graing strategy in the most recent 2018 European Society of Cardiology/ European Association for Cardiooracic Surgery Guidelines on myocardial revascularization.

e key for successful use of the RA is the careful preoperative evaluation of the severity of stenosis of the target vessel(s), as it has been clearly shown that the RA patency rate is tightly correlated with the severity of the native coronary disease. Traditional stenosis cutos are 70% in the le coronary system and 90% in the right coronary ar ter y, but a 1.7– 2.0 ratio between the diameter of the distal RA and the residual luminal diameter of the target vessel is a more physiological approach used by most RA experts, although never formally tested (M. Gaudino, personal communication). Alesser degree of target vessel stenose may be acceptable for side- to- side anastomoses of sequential gras as long as the nal end- to- side anastomosis is performed on a severely stenotic coronary vessel.

e SV is still the most frequently used conduit for CABG, despite its known limitations in terms of long- term patency rates. e SV is extremely easy to handle and to harvest and is the gra of choice for the non- le anterior descending targets in emergency situations, for complex associated coronary and valvular or aortic cases, or in patients with extensive comorbidities. e use of guidelines- directed medical therapy is likely to have a substantial impact on SV gras failure and new techniques and devices (no- touch technique, external stents) seem to have promising potential to increase SV patency rates. Specic details on these techniques and devices are given in the appropriate chapters.

Despite past concerns, the use of endoscopic vein harvesting does not seem to adversely aect the clinical outcomes of CABG while signicantly reducing the incidence of harvest site complications.

e RA is easier to handle than other arterial conduits and simplies the execution of even complex graing strategies. e length is adequate to gra any potential coronary target and is usually ad-

Conclusion

equate to perform sequential, Y and ‘baby Y’ gras. Although several authors have reported excellent results with ITA- based RA Y gras, in the Y conguration the RA patency is even more affected by competitive coronary ow and the surgical strategy must be carefully tailored to the status of the coronary circulation (the

e choice of conduits and graing strategy should be tailored to each individual patient and is key to the success and benet of the CABG operation. It is important that the modern coronary surgeon be familiar with all the available conduits and graing techniques.

28 The selection ofconduits forcoronary artery bypasssurgery 235

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Elective CABG candidate with no contraindication to RA or GEA harvesting*

No major risk factors for postoperative mediastinitis

Target vessel stenosis >70%

Lateral wall

70–90% stenosis

ITA/RA

Target vessel stenosis ≤70%

Inferior wall Inferior wall

>90% stenosis

RA/GEA

SVG

Lateral wall

ITA

†

SVG

Major risk factors for postoperative mediastinitis

Target vessel stenosis >70% Target vessel stenosis ≤70%

Lateral wall

Inferior wall

70–90% stenosis

>90% stenosis

RA/GEA

SVG

†

SVG

Fig.28.2 Ascheme for the choice of conduits for coronary artery bypass surgery. Composite and elongated grafts are not considered. *In the

case of contraindications to RA or GEA harvesting, SVG should be used. †Deﬁned as obesity, diabetes, and severe chronic lung disease, especially in combination. CABG, coronary artery bypass graft; GEA, gastroepiploic artery; ITA, internal thoracic artery; RA, radial artery; SVG, saphenous vein graft.

Reproduced from Gaudino M, Taggart D, Suma H, Puskas JD, Crea F, Massetti M.The Choice of Conduits in Coronary Artery Bypass Surgery. J Am Coll Cardiol. 2015 Oct 13;66(15):1729– 37 with permission from Elsevier.

Ascheme for the choice of conduits based on the available evidence is given in Fig. 28.2.

8. Tatoulis J, Buxton BF, Fuller JA. e right internal thoracic artery:is it underutilized? Curr Opin Cardiol. 2011;26(6):528– 35.

9. Hwang HY, Oh HC, Kim YH, Kim K- B. Complete

REFERENCES

1. ElBardissi AW, Aranki SF, Sheng S, O’Brien SM, Greenberg CC, Gammie JS. Trends in isolated coronary artery bypass graing:an analysis of the Society of oracic Surgeons adult cardiac surgery database. J orac Cardiovasc Surg. 2012;143(2):273– 81.

2. Gaudino M, Taggart D, Suma H, Puskas JD, Crea F, Massetti M. e choice of conduits in coronary artery bypass surgery. J Am Coll Cardiol. 2015;66(15):1729– 37.

3. Aldea GS, Bakaeen FG, Pal J, Fremes S, Head SJ, Sabik J, etal. e Society of oracic Surgeons clinical practice guidelines on arterial conduits for coronary artery bypass graing. Ann orac Surg. 2016;101(2):801– 9.

4. Favaloro RG. Saphenous vein autogra replacement of severe segmental coronary artery occlusion:operative technique. Ann orac Surg. 1968;5(4):334– 9.

5. Tatoulis J, Buxton BF, Fuller JA. Patencies of 2,127 arterial to coronary conduits over 15years. Ann orac Surg. 2004;77(1):93– 101.

6. Benedetto U, Raja SG, Albanese A, Amrani M, Biondi- Zoccai G, Frati G. Searching for the second best gra for coronary artery bypass surgery:a network meta- analysis of randomized controlled trials. Eur J Cardiothorac Surg. 2015;47(1):59– 65.

7. Buttar SN, Yan TD, Taggart DP, Tian DH. Long- term and shortterm outcomes of using bilateral internal mammary artery graing versus le internal mammary artery graing:a meta- analysis. Heart. 2017;103(18):1419– 26.

revascularization of the three- vessel territories using a le internal thoracic artery composite gra. Ann orac Surg. 2015;100(1):59– 66.

10. Hayward PA, Buxton BF. Mid- term results of the Radial Artery Patency and Clinical Outcomes randomized trial. Ann Cardiothorac Surg. 2013;2(4):458– 66.

11. Deo SV, Shah IK, Dunlay SM, Erwin PJ, Locker C, Altarabsheh SE, etal. Bilateral internal thoracic artery harvest and deep sternal wound infection in diabetic patients. Ann orac Surg. 2013;95(3):862– 9.

12. Gaudino M, Mack MJ, Taggart DP. Additional arterial conduits in coronary artery bypass surgery:nally coming of age. J Am Coll Cardiol. 2018;71(25):2974– 6.

13. Sousa- Uva M, Neumann F- J, Ahlsson A, Alfonso F, Banning AP, Benedetto U, etal. 2018 ESC/ EACTS Guidelines on myocardial revascularization. Eur J Cardiothorac Surg. 2019;40(2):87– 165.

14. Royse AG, Brennan AP, Ou- Young J, Pawanis Z, Canty DJ, Royse CF. 21- year survival of le internal mammary artery- radial artery- Y gra. J Am Coll Cardiol. 2018;72(12):1332– 40.

15. Gaudino M, Alessandrini F, Pragliola C, Cellini C, Glieca F, Luciani N, etal. Eect of target artery location and severity of stenosis on mid- term patency of aorta- anastomosed vs. internal thoracic artery- anastomosed radial artery gras. Eur J Cardiothorac Surg. 2004;25(3):424– 8.

16. Deb S, Singh SK, Moussa F, Tsubota H, Une D, Kiss A, etal. e long- term impact of diabetes on gra patency aer coronary artery

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bypass graing surgery:a substudy of the multicenter Radial Artery Patency Study. J orac Cardiovasc Surg. 2014;148(4):1246– 53.

17. Gaudino M, Fremes S, Schwann TA, Tatoulis J, Wingo M, Tranbaugh RF. Technical aspects of the use of the radial artery in coronary artery bypass surgery. Ann orac Surg. 2019;108(2):613– 22.

18. Suma H, Tanabe H, Yamada J, Mikuriya A, Horii T, Isomura T. Midterm results for use of the skeletonized gastroepiploic artery gra in coronary artery bypass. Circ J. 2007;71(10):1503– 5.

19. Kang S, Liu Y, Liu X. Eects of aggressive statin therapy on patients with coronary saphenous vein bypass gras:a systematic review and meta- analysis of randomized, controlled trials. Clin er. 2013;35(8):1125– 36.

20. Zenati MA, Bhatt DL, Bakaeen FG, Stock EM, Biswas K, Gaziano JM, etal. Randomized trial of endoscopic or open vein- gra harvesting for coronary- artery bypass. N Engl J Med. 2019 10;380(2):132– 41.

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Storage solutions forveingras

Minh Quan Vu, Pierre- Emmanuel Noly, Walid Ben Ali, and Louis P. Perrault

Introduction

e loss of endothelial cells and the denudation of the intimal

layer during the vein harvesting and manipulations, ischaemic–

Even though total arterial revascularization is increasingly used, saphenous vein gras (SVGs) are still the most commonly used conduits for coronary arterial bypass graing (CABG) worldwide. Every surgeon should keep in mind that a vascular gra is living tissue with active metabolism, analogous to a solid organ for transplant, and should understand the impact of the choice of the storage solution.

Unfortunately, the choice of the storage solution is usually not

reperfusion injury, and inammation can all lead to the loss of endothelium function (nitric oxide production, vasodilatation, activation of VCAM- 1, ICAM- 1, and selectins) and expose the gra to acute thrombosis, stenosis, or occlusion. Facing higher intraluminal pressure and shear stress, there is an increased production of growth factors and remodelling of matrix components due to increased protease activity. is phenomenon can lead to gra dilatation and VGF.

the result of a thoughtful review of alternatives and evidence but is a function of habit, convenience, and availability. e ideal storage solution should preserve and restore endothelial functional aer harvesting. Much eort has been invested in nding ways to avoid or prevent endothelial lesions during harvesting and storage, as well as delaying vein gra dilatation aer CABG.

Aer a brief reminder of the vein gra failure (VGF) pathophysiology, we discuss storage conditions using the existing gra storage solutions and their inuence on endothelial function and gra patency. e use of external stenting for vein gras is addressed in Chapter31.

Storagesolutions

Existing vein graft storagesolutions

See Table 29.1.

0.9% normalsaline

Normal saline (NS) is one of the most frequently used solutions and is usually mixed with heparin. However, many studies have shown that NS impairs endothelial function, even during short- term storage, and may

Overview ofthe pathophysiology ofvenous graftfailure

e largest prospective study of VGF rates, the Project of Ex- Vivo Vein Gra Engineering via Transfection IV (PREVENT IV) trial, revealed that almost half of gras had VGF and one- third of the patients presented with VGF at only 1year. VGF comprises three temporally distinct but pathophysiological related processes:thrombosis, intimal hyperplasia, and atherosclerosis. rombosis- mediated gra failure is an early event causing about 10– 15% of SVGs to occlude within the rst month of bypass surgery.

Initially, intimal hyperplasia is an endothelial- mediated physiological mechanism in response to the new pulsatile and high blood pressure regimen in the vein. e increase of wall tension and the shear stress caused by viscous friction on the vascular wall leads to a smooth cell muscle proliferation. is is the foundation for later gra atheroma development, leading to intermediate- to late- stage VGF.

promote neointimal hyperplasia and intramural oedema. It contains approximately 154mmol/ L of sodium chloride, is acidic (pH=5.0), and is slightly hypertonic with an estimated osmolarity of 308 mOsm/ L.

Autologous wholeblood

Usually used at 4°C, the composition of autologous whole blood (AWB) varies among patients and conditions. On contact with air, blood loses carbon dioxide and becomes alkaline. Comparison between AWB and NS yields conicting conclusions. Some authors report better preservation of the endothelium- dependent vasoactive responses with heparinized AWB compared to NS. However, when compared to buered or enhanced solutions such as the University of Wisconsin solution (UWS), AWB and NS showed worse outcomes. e literature remains inconclusive about the superiority of AWB compared to saline and thus, AWB failed to replace NS use.

Bufferedsolutions

Buered solutions showed superior ex vivo preservation of the structural and functional endothelial integrity compared to blood

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