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Table29.1 Compositions ofstorage solutions inuse

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Solutions pH Osmolarity

Buffured solutions

Extracellular Blood plasma 7.35– 7.42 295– 310 135– 145 95– 105 3.5– 4.5 0.7– 1 2.2– 2.6 1 29 –

0.9% NS 4.5– 7.0 308 154 154 – – – – – None

AWB 7.4 280– 310 140 110 5 2 – 2 – None

GALA 7.4 309 142– 156 145 5.8– 6 0.89– 1 0.95– 1 0.5 4 Glutathione, l- ascorbic acid, l- arginine, glucose

Celsior™ 7.3 360 100 42 15 13 0.25 – – Glutathione, mannitol, lactobionic acid,

Dr He’s Solution 7.4 – 147 156 4 – 2.3 – 0.2 mL

Intracellular TiProtec™ 7.0 at 20°C 305 16 103.1 93 8 0.05 – –

UWS 7.4 360 27 125 5 – 5 – Lactobionic acid, adenosine, allopurinol,

HTK 7.4 at 4°C 310 15 50 9 4 0.015 – –

(mOsm/ L)

Na+ (mmol/ L)

Cl− (mmol/ L)

K+ (mmol/ L)

Mg2+ (mmol/ L)

Ca2+ (mmol/ L)

2−

(mmol/ L)

−

HCO

(mmol/ L)

of 8.4%

Other components

glutamic acid, histidine

Verapamil hydrochloride, glyceride trinitrate, heparin

α- Ketoglutarate, aspartate, N- acetyl histidine, glycine, alanine, tryptophan, sucrose, glucose, deferoxamine, 3,4- dimethoxy- N- methylbenzohydroxamic acid

rafﬁnose, glutathione, polyhydroxyethyl starch

Histidine, α- ketoglutarate, tryptophan, mannitol

29 Storage solutions forveingrafts 239

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and saline solutions. e advantages are that they can maintain a physiological pH during storage, they contain nutrients and antioxidants, and have a better ionic balance.

• e UWS is an intracellular- like preservation medium commonly

used in organ preservation since the 1980s. It contains free rad-

ical scavengers (glutathione), buering anions, as well as sugars

and colloids (hydroxyethyl starch) to decrease cellular swelling.

Osmotic concentration is maintained by inert additives such as

ranose and lactobionic acid.

• Glutathione- ascorbic - arginine (GALA) solution is a physio-

logical solution based on Hank’s balanced saline solution. Hank’s

balanced salt solution was modied by adding 0.09 g/ L of reduced

glutathione (1000mmol/ L nal concentration) and 0.31 g/ L of -

ascorbic acid (500 mol/ L nal concentration) as antioxidants and

reducing agents, with 0.15 g/ L of - arginine (500 mmol/ L nal

concentration) as a substrate for endothelial nitric oxide synthase.

Heparin (50 U/ mL) is added as an anticoagulant and the pH is ad-

justed to 7.4 using 8.4% sodium bicarbonate solution. Arandom-

ized controlled trial comparing NS to GALA is currently ongoing

(see later).

• Celsior® solution was designed specically for organ preservation.

It is an extracellular solution that has low viscosity, high sodium,

and low potassium. It was initially designed as a cardioplegic solu-

tion for heart transplants. Celsior® was later used for its safety and

eectiveness in preserving the heart and lungs.

• TiProtec™ is a recently developed N- acetyl histidine- buered

storage solution composed by a low concentration in sodium

(16 M) enriched with potassium (93 M), N- acetyl histidine (30

M), glycine (10 M), and added iron chelator deferoxamine. is

intracellular has shown promising results in terms of endothelial

preservation.

• He solution:He and colleagues proposed an easy- made solution,

which contain a combination of glyceryl trinitrate and verapamil

in buered Ringer’s solution. In their study from human SVGs

from 50 patients, they found that irrigation while harvesting and

storage of the SVG with this solution relaxes SVG in vitro within

1– 2 minutes and maintains this action for more than 2 hours.

• Histidine– tryptophan– ketoglutarate (HTK) solution is a low- vis-

cosity and low- potassium crystalloid preservation solution. HTK

was originally designed as a cardioplegia solution with osmolarity

slightly higher than the intracellular space. Histidine serves as a

buer, tryptophan is a membrane stabilizer, and ketoglutarate is

an energy substrate.

Evidenced- based studies and current practice onvein graftsstorage

ere is only one randomized clinical trial addressing this issue. Other studies using in vitro techniques and animal models can be extrapolated to answer the following questions.

Is autologous whole blood better than normal saline for vein graft storage?

ree studies have shown better preservation of endothelium with AWB, two others showed no dierence, while two showed lower preservation compared to NS. e authors concluded that there is little evidence of the superiority of AWB. All studies are consistent in demonstrating the detrimental eect of NS on vascular

endothelium. In the study of Lawrie etal., the endothelial function of 85 human vein gras was severely compromised aer preparation with NS compared to AWB and Plasma- Lyte®. In 2013, Wilbring etal. reported improved endothelial function in human SVG with AWB. ey discourage the use of NS and suggested that alternative storage solutions would be preferable.

Should we preferentially use buffered solutions for vein graft storage?

In 2014, a retrospective subanalysis of the PREVENT IV trial showed better SVG patency in gras preserved in buered solution compared to NS and AWB. Balanced, buered electrolyte solutionpreserved gras had 1- year VGF rates signicantly less than two other groups, and were associated with a lesser risk of 5- year death, myocardial infarction, and secondary revascularization.

In 2014, Wise et al. showed better endothelial relaxation and contraction of SVG aer a bath in Celsior®, UWS, and GALA solutions compared to NS or AWB. When compared to NS and HTK, TiProtec™ solution appears superior in terms of endothelial pres- ervation and is able to reduce the loss of endothelium- dependent vascular function during cold storage. Recent evidence suggests the preferable use of buered preservation solutions (Table 29.2).,–  Further studies are needed to determine which solution brings the most benet.

Does thetemperature matter?

e ideal temperature for the best endothelial protection is still debated. Most of the studies were performed at low temperature (4– 10°C) and when compared to room temperature, the same solution used at cold temperature seems more ecient.

Vein graft pressuredistension

During routine competence testing of SVGs, hydrostatic pressure is usually uncontrolled and underestimated. Amedian peak pressure of 350mmHg can be reached with a range of 240– 639mmHg.

Experimental data show that at a distension pressure of over 50 mmHg, more than half of endothelial cells were lost. ese nding were also conrmed by Weiss etal. At a distension pressure of more than 50mmHg, there is also a prominent loss of microbrils, increasing the stiness of the gra and impairing SVG function.

Metabolic changes of the vein gra endothelium aer pressure distension were also observed. With higher distension pressures applied, adenosine triphosphate (ATP) concentrations and the ratio of ATP/ adenosine diphosphate (ADP) decrease was greater while adenosine concentration increased, most likely the result of disruption of the endothelial layer and induced medial damage. Diminished endothelial nitric oxide synthase staining and increased levels of reactive oxygen species were also reported.

Pressure- related immunohistochemical alterations were also found in veins having undergone distention with upregulation of various biomarkers of inammation including scavenger receptors Aand B and cell adhesion molecules.,

Chung etal. observed, in porcine veins subjected to distension with 300mmHg of pressure, increased proteolytic activity of matrix metalloproteinases (MMPs) and downregulated protein expression of tissue inhibitors of MMP (TIMP)- 1 and TIMP- 2, both events that promote smooth cell muscle migration into the intima. Moreover, Stigler etal. observed signicant neointimal proliferation

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Table29.2 Summary ofstudies comparing standard and buffered preservation solutions

Study Design Solution Key endpoints

Catinella etal.

(1982)

Cavallari etal.

(1997)

Thatte etal.

(2003)

Weiss etal.

(2009)

Wilbring etal.

(2013)

Wise etal.

(2014)

Harskamp etal.

(2014)

In vivo/ in vitro human study Angiography at 10days

In vitro animal study NS

In vitro human study NS

Clinical retrospective study

Buffered saline AHB

AHB UWS

AHB GALA

NS + albumin AHB HTK

TiProtec™

UWS Plasma- Lyte®

NS AHB Buffered saline

Higher VGF rate in the AHB group at 10days (20% vs 7%; P <0.01) Endothelial cell desquamation and severe venous smooth muscle cell spam in the AHB group

Endothelial integrity and maximal contractile response preserved in the UWS group when compared to standard preservation solutions

Greater cell integrity maintenance in the GALA group (76– 100%) at 24 hours Calcium mobilization and NO production increased at 5 hours in the GALA group and not detectable in the NS and AHB groups at 3 hours

The HTK solution failed to maintain cell integrity

The endothelium- dependent vasodilation abolished in the NS group and preserved in the TiProtec™ group at 96 hours

Reduced KCl- induced contractility in the NS group when compared to UWS

1- year VGF rates were lower in the buffered solutions than in the saline group (graft- level odds ratio 0.63; P <0.001) or the blood group (graft- level odds ratio 0.62; P <0.001) 5- year HR for death, myocardial infarction, and repeat revascularization was 0.81 (buffered saline vs AHB/ NS)

AHB, autologous heparinized blood; GALA, glutathione, ascorbic acid, l- arginine; HTK, histidine– tryptophan– ketoglutarate; HR, hazard ratio; NO, nitric oxide; NS, normal saline; UWS, University of Wisconsin solution; VGF, vein graft failure.

at distension pressures as low as 100mmHg. is pathological response which precedes VGF, increased with incremental distension pressures, reaching almost four times baseline intimal thickness at 300mmHg. Pressure- induced intimal hyperplasia was also reported by Osgood etal.

Many studies reported in porcine saphenous vein models that pressure- related vein damages can be prevented with the simple use of pressure release valves.–  Pressure- controlled syringes (e.g. Vasoshield pressure controlling syringe, Maquet Inc., Rastatt, Germany) are commercially available but costs and lack of robust clinical data limit their application at a large scale. Obviously, the ultimate way to limit pressure distension vascular damage is to avoid it, such as is recommended in Souza’s no- touch technique.

Genetic therapeutic:lessons fromthe PREVENT IVtrial

PREVENT IV trial was a phase III, multicentre, randomized, doubleblind, placebo- controlled trial that evaluated the eect of ex vivo treatment of vein gras with an oligonucleotide decoy to E2F transcription factors (edifoligide) in 3000 patients who underwent CABG surgery. E2F transcription factors are implicated in the up- regulation of genes believed to play a key role in the initiation of neointimal hyperplasia. It was the rst major clinical trial of applied genetic therapy on vein gras in CABG surgery. e primary end point was the incidence of critical gra restenosis (>75% stenosis) assessed by angiography aer a year of follow- up. is trial revealed that edifoligide was no more eective than placebo in preventing gra failure.

Targeted therapeutics:SELECT- CABGtrial

Some experimental and clinical evidence has supported the poten-

the eect of inclacumab, a human monoclonal antibody directed against P- selectin, on VGF assessed by quantitative coronary angiography 1year aer CABG surgery. is prospective randomized, multicentre, double- blind, placebo- controlled trial included 384 patients. e results of this study showed that the specic anti- Pselectin antibody did not exert signicant favourable eects on VGF.

Ongoing clinicaltrials

Only one study on gra storage solution is ongoing in ClinicalTrial. gov. It aims to evaluate the use of the DuraGra® (Somah lution, Jupiter, FL, USA) solution (SOMVC001) in patients undergoing CABG (ClinicalTrial.gov ientier:NCT02272582). is prospective randomized, double- blinded trial started in 2014 and is currently extended to increase time of follow- up to 1year. e primary objective is to assess the impact of SOMVC001 (GALA) in comparison to heparinized saline. It evaluates the eect on gra patency of gras at 12months following CABG surgery using 64- slice or better multidetector computed tomography angiography. Each patient will serve as his/ her own control because each patient will have one segment immersed in SOMVC001 and the other in heparin- dosed saline. SVG harvesting is performed using an open or endoscopic vein harvesting technique. In addition to gra patency, this study will also identify eects related to the vessel remodelling such as changes in the lumen and wall thickness over time. ese eects will be evaluated as secondary end points. Enrolment was due to end in December 2016 (n=120 patients) and positive results have been recently published.

Conclusion

tial therapeutic role of P- selectin inhibitors. e SELECT- CABG trial (Eects of P- Selectin Antagonist Inclacumab in Patients Undergoing Coronary Artery Bypass Gra Surgery) aimed to assess

VGF is a major concern aer CABG. One answer to decrease this complex phenomenon may be the use of the right solution for storage

29 Storage solutions forveingrafts 241

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of the vein gras aer meticulous harvesting. Most studies showed that no storage solution can reverse the endothelial damage caused by a traumatic harvesting or high pressure. Among the available storage solutions, buered salines showed the best results as they have the added benets of antioxidants, chelators, a more physiological pH, nitric oxide precursor L- arginine, and physiological electrolytes concentrations. Despite both experimental and clinical results in favour of buered solutions, NS is still being the most widely used solution. Ongoing clinical studies will probably provide stronger evidence for the use of storage solutions.

REFERENCES

1. 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.

2. Harskamp RE, Alexander JH, Schulte PJ, Brophy CM, Mack MJ, Peterson ED, etal. Vein gra preservation solutions, patency, and outcomes aer coronary artery bypass gra surgery:follow- up from the PREVENT IV randomized clinical trial. JAMA Surg. 2014;149(8):798– 805.

3. Schachner T. Pharmacologic inhibition of vein gra neointimal hyperplasia. J orac Cardiovasc Surg. 2006;131(5):1065– 72.

4. He GW, Rosenfeldt FL, Angus JA. Pharmacological relaxation of the saphenous vein during harvesting for coronary artery bypass graing. Ann orac Surg. 1993;55(5):1210– 7.

5. Lawrie GM, Weilbacher DE, Henry PD. Endothelium- dependent relaxation in human saphenous vein gras. Eects of preparation and clinicopathologic correlations. J orac Cardiovasc Surg. 1990;100(4):612– 20.

6. Wilbring M, Tugtekin SM, Zatschler B, Ebner A, Reichenspurner H, Kappert U, etal. Preservation of endothelial vascular function of saphenous vein gras aer long- time storage with a recently developed potassium- chloride and N- acetylhistidine enriched storage solution. orac Cardiovasc Surg. 2013;61(8):656– 62.

7. Wise ES, Hocking KM, Cheung- Flynn J, Brophy CM. Balanced, pH- buered preservation solutions improved physiologic response in human saphenous vein gra. Arterioscler romb Vasc Biol. 2014;34:A322.

8. Catinella FP, Cunningham JN, Jr, Srungaram RK, Baumann FG, Nathan IM, Glassman EA, etal. e factors inuencing early patency of coronary artery bypass vein gras:correlation of angiographic and ultrastructural ndings. J orac Cardiovasc Surg. 1982;83(5):686– 700.

9. Cavallari N, Abebe W, Mingoli A, Hunter WJ, Agrawal DK, Sapienza P, etal. Functional and morphological evaluation of canine veins following preservation in dierent storage media. J Surg Res. 1997;68(2):106– 15.

10. atte HS, Biswas KS, Najjar SF, Birjiniuk V, Crittenden MD, Michel T, etal. Multi- photon microscopic evaluation of saphenous vein endothelium and its preservation with a new solution, GALA. Ann orac Surg. 2003;75(4):1145– 52.

11. Weiss DR, Juchem G, Kemkes BM, Gansera B, Nees S. Extensive deendothelialization and thrombogenicity in routinely prepared vein gras for coronary bypass operations:facts and remedy. Int J Clin Exp Med. 2009;2(2):95– 113.

12. Stigler R, Steger C, Schachner T, Holfeld J, Edlinger M, Grimm M, etal. e impact of distension pressure on acute endothelial cell loss and neointimal proliferation in saphenous vein gras. Eur J Cardiothorac Surg. 2012;42(4):e74– 9.

13. Weiss DR, Juchem G, Eblenkamp M, Kemkes BM, Gansera B, Geier M, etal. Search for optimized conditions for sealing and storage of bypass vessels:inuence of preservation solution and lling pressure on the degree of endothelialization. Int J Clin Exp Med. 2010;3(1):10– 27.

14. Ozturk N, Sucu N, Comelekoglu U, Yilmaz BC, Aytacoglu BN, Vezir O. Pressure applied during surgery alters the biomechanical properties of human saphenous vein gra. Heart Vessels. 2013;28(2):237– 45.

15. Angelini GD, Passani SL, Breckenridge IM, Newby AC. Nature and pressure dependence of damage induced by distension of human saphenous vein coronary artery bypass gras. Cardiovasc Res. 1987;21(12):902– 7.

16. Osgood MJ, Hocking KM, Voskresensky IV, Li FD, Komalavilas P, Cheung- Flynn J, etal. Surgical vein gra preparation promotes cellular dysfunction, oxidative stress, and intimal hyperplasia in human saphenous vein. J Vasc Surg. 2014;60(1):202– 11.

17. Khaleel MS, Dorheim TA, Duryee MJ, Durbin HE, Bussey WD, Garvin RP, etal. High- pressure distention of the saphenous vein during preparation results in increased markers of inammation:a potential mechanism for gra failure. Ann orac Surg. 2012;93(2):552– 8.

18. Chello M, Mastroroberto P, Frati G, Patti G, D’Ambrosio A, Di

of endothelial adhesion molecules in the human saphenous vein gra. Ann orac Surg. 2003;76(2):453– 8.

19. Chung AW, Rauniyar P, Luo H, Hsiang YN, van Breemen C, Okon EB. Pressure distention compared with pharmacologic relaxation in vein graing upregulates matrix metalloproteinase2 and - 9. J Vasc Surg. 2005;42(4):747– 56.

20. Li FD, Eagle S, Brophy C, Hocking KM, Osgood M, Komalavilas P, etal. Pressure control during preparation of saphenous veins. JAMA Surg. 2014;149(7):655– 62.

21. Cheung- Flynn J, Song J, Voskresensky I, Wise ES, Liu Y, Xiong Y, etal. Limiting injury during saphenous vein gra preparation for coronary arterial bypass prevents metabolic decompensation. Sci Rep. 2017; 7(1):14179.

22. Wise ES, Hocking KM, Evans BC, Duvall CL, Cheung- Flynn J, Brophy CM. Unregulated saphenous vein gra distension decreases tissue viscoelasticity. Perfusion. 2017;32(6):489– 94.

23. Souza D. A new no- touch preparation technique. Technical notes. Scand J orac Cardiovasc Surg. 1996;30(1):41– 4.

24. Stähli BE, Tardif JC, Carrier M, Gallo R, Emery RW, Robb S, etal. Eects of P- selectin antagonist Inclacumab in patients undergoing coronary artery bypass gra surgery:SELECT- CABG Trial. J Am Coll Cardiol. 2016;67(3):344– 6.

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*Two ongoing multicenter

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No- touch saphenous vein gras incoronary artery bypasssurgery

A comprehensive review

Ninos Samano and Domingos Souza

Historicalperspective

Harvesting conduits with a pedicle was well know when preparing the le internal thoracic (mammary) artery (LITA). However, this

e need to improve the performance of the saphenous vein gra (SVG) in coronary artery bypass (CABG) surgery has been a challenging task for several decades. e use of arterial gras has been

concept was never applied to the SV. is led to the rst harvesting of the saphenous vein with a pedicle of surrounding tissue, thus avoiding gra spasm and the need for manual dilatation.

proven to be eective, especially with regard to the long- term survival and patency rates. Despite this, the SVG is still the most common gra used in CABG. is is due to numerous advantages,

First randomized controlledtrial

including ease of access and manipulation, sucient length for graing, and short harvesting time, in addition to the fact that prolonged gra durability is not always the primary concern, especially in elderly patients with multiple comorbidities.

e no- touch (NT) technique for harvesting the saphenous vein was rst considered in 1989. e saphenous vein was observed to remain relaxed and dilated just before removing the surrounding tissue, only to develop spasm aer this tissue was removed.

NT SVG vs endoscopic SVG

RCT, NT SVG vs RA

NT SVG & vasa vasorum

RCT 8.5 yrs, NT SVG comparable to LIMA

NT SVG & intact endothelium

First observation & harvesting

First RCT, NT SVG vs C vs IM

RCT, 1.5 yrs’ follow-up

RCT 8.5 yrs, clinical follow-up

NT SVG & high-pressure distension

NT SVG & atherosclerosis

e NT technique was initially described in detail and published in 1996. However, 3 years earlier, the rst randomized clinical trial (RCT) was started (Fig. 30.1). e trial compared three SVG harvesting techniques in CABG. In the conventional (C)group, the vein was stripped of its surrounding tissue and manually distended with saline before graing. In the intermediate (IM) group, the vein was stripped but not distended and in the NT group, it was neither

*Endoscopic NT SVG harvesting

*PCI in NT SVGs

NT SVG to the LAD artery

RCT 16 yrs, NT SVG still

comparable to LITA

RCT 8 yrs, NT SVG vs RA

NT SVG recommended in

ESC/EACTS guidelines

*Combination of arterial and NT SVGs as ‘gold standard’ in CABG

*NT SVG as ﬁrst choice in sequential graft

RCTs, NT SVG vs C;

China: NCT03126409

Sweden: NCT03501303

Fig.30.1 Milestones in the development of the no- touch saphenous vein graft (NT SVG) in coronary artery bypass grafting (CABG). C, conventional;

EACTS, European Association for Cardio- Thoracic Surgery; ESC, European Society of Cardiology; IM, intermediate; LAD, left anterior descending; LITA, left internal thoracic artery; PCI, percutaneous coronary intervention; RA, radial artery; RCT, randomized controlled trial.

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stripped nor distended. All patients received a LITA to the le anterior descending (LAD) artery. e patients in C and NT groups were followed up at 1.5, 8.5, and 16years postoperatively.–  e patency rate in the C group was signicantly lower than that in the NT group; 89% versus 95%, 77% versus 91%, and 64% versus 83% at all three follow- ups respectively. In the last two instances, the patency rate of the NT SVGs to non- LAD targets was comparable to that of the LITA to LAD. is indicates that the target vessel size,

ejection fraction aer 16years. e IM group was not included in the last two follow- ups due to nancial limitations and relevance— the patency of the IM group was inferior to both the C and NT arms at 1.5years postoperatively. Clinical outcomes were also evaluated during the trial and the results published in 2009. ere were signicantly more patients free from angina and in NewYork Heart Association classIin the NT group at a mean time of 8.5years

postoperatively. the vessel quality, and degree of stenosis have little, or no, eect on NT SVG performance, in contrast to arterial gras. is may be due to the fact that undamaged or minimally manipulated NT SVGs

Atherosclerosis

anastomosed to dierent target vessels possess a greater ability to remodel, either increasing or decreasing in size based on ow demand. In addition to this, the NT SVG preserved the le ventricular

During the two follow- ups of the rst RCT, an intravascular ultra-

sound was performed on a group of patients who were considered

Fig.30.2 Postmortem biopsies of no- touch saphenous vein grafts obtained 3, 8, 10, and 19years postoperatively.

30 No-touch saphenous vein grafts incoronary artery bypasssurgery 245

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to have patent SVGs. Patients from both the C and NT groups were included and the degree of patency was established by coronary angiography. e gras were evaluated with respect to lumen volume, intimal thickness, incidence of plaque, and plaque components. Intravascular ultrasound showed signicantly fewer gras containing multiple plaques, less advanced plaque with lipid, and

distension and removal of, or damage to, perivascular tissue. In addition, the perivascular adipose tissue is a source of adipocytederived, anticontractile factors, such as NO and leptin, which may play a role in reducing spasm and maintaining gra patency. e consequences of high- pressure distension are further discussed in a

letter published in 2017. less maximal plaque thickness in the NT group. Several postmortem biopsies from dierent time periods postoperatively corroborated these ndings. e biopsies showed considerable necrotic and friable tissue as well as a diuse atherosclerotic process in the C group

No- touch saphenous vein grafts versus theradialartery

compared to the less pronounced and more localized atherosclerotic process in NT gras (Fig. 30.2).

Another RCT was started in 2004 including 108 patients. Each pa-

tient received one LITA, one radial artery, and one NT SVG as con-

Endothelialintegrity

duit material. e LITA was used to bypass the LAD artery, and the

radial artery and NT SVG were randomized to bypass either the le

or the right coronary territory. e patients were followed up with Endothelial cell integrity of the SVG harvested by the three dierent

techniques was examined early in the RCT. Morphological techniques, including scanning and transmission electron microscopy, were used. Preservation of endothelial cell integrity was greater with the NT harvesting than with the other methods. is nding was shared in a following study in which additional analyses were performed. Acombination of histochemistry and autoradiography was used to identify

at 3 and 8 years postoperatively. No- touch SVGs showed a signi-

cantly higher patency rate than that of the radial artery, at 3 years

94% versus 82% respectively. Of note however, the majority of radial

artery gras were used to bypass coronary arteries with native sten-

osis below the threshold usually recommended by contemporary

guidelines. At 8 years’ follow-up, the patency was similar, 86% vs

79% for NT SVGs respective radial artery gras, p=0.22. nitric oxide synthase (NOS) in SVGs. NOS is needed to produce nitric

oxide (NO). e latter mediates vasodilatation and has an inhibitory eect on platelet aggregation and adhesion. e study concluded that

Vasavasorum

some of the sites with potential for NO release (endothelium and adventitial vasa vasorum) were removed in C compared to NT SVGs.

In the previously described RCT, samples of dierent conduits

(LITA, NT SVG, C SVG, and radial artery) where collected for fur-

High- pressuredistension

ther analysis. e aim of this study was to quantify the vasa vasorum

in the dierent gras and also to determine endothelial NO levels

and NOS activity. e vasa vasorum is a network of nourishing Further studies were conducted to investigate the eect of highpressure distention on endothelial integrity and NOS in SVGs. Combinations of immunohistochemistry, Western blot analysis, reverse transcriptase polymerase chain reaction, and enzyme assay were applied in distended (with and without perivascular tissue) compared with nondistended segments. Endothelial NOS expression and activity were signicantly reduced by high- pressure

microvessels supplying nutrients and oxygen to the blood vessel

wall (Fig. 30.3). is analysis showed far more vasa vasorum in

SVGs than LITA and radial artery gras. Skeletonization of sa-

phenous veins reduced the number of these microvessels. us,

NT SVG harvesting preserves the vasa vasorum and maintains

transmural blood supply, in addition to the conservation of an im-

portant supply of endothelial- derived NO.

Fig.30.3 Ano- touch saphenous vein graft (NT SVG) showing abundant vaso vasorum.

SECTION 6 Conduits forcoronary artery bypass graft surgery246

https://t.me/medicina_free

No- touch versus endoscopic conventional harvesting ofthe saphenous veingraft

Endoscopic saphenous vein (endo- vein) harvesting is an established method especially in the United States and some parts of Europe. is is due to the lower rate of associated harvest site complications. Acomparison of gra patency and wound complications was performed in 210 CABG patients who received either a NT SVG (87 patients) or endo- vein (123 patients). A symptom- directed cardiac catheterization was performed on these patients showing a signicantly higher patency rate in the NT group compared to the endo- vein group, 94% and 27% respectively. However, harvest site complications were signicantly higher in the NT patients, 18% compared to 2% in the endo- vein patients.

its course. Astudy published in 2014 showed similar functional leg recovery between the C and NT harvesting techniques 12months aer surgery. Needless to say, we would prefer a conduit that performs longer even if the risk for wound complications is higher. An ideal situation would be to have a superior conduit with minimal risk for surgical complications. is could eventually be achieved with developing an endoscopic harvesting technique for the NT SVG. We sincerely encourage all attempts to improve the NT technique but we advise caution in coming to conclusions with the lack of long- term reliable data.

Over the years, percutaneous coronary intervention in SVGs has been shown to have poor outcomes. is is mainly due to the diffuse atherosclerotic changes occurring in these gras. e NT SVGs oen develop more localized changes and percutaneous coronary intervention in these gras could produce better results. is is currently being studied in our department.

No- touch saphenous vein graft tothe left anterior descendingartery

e use of the LITA as the rst choice to bypass the LAD artery, is a settled issue. is is accomplished in almost 95% of CABG patients. Nevertheless, the remaining 5% of patients is a large number,

In our opinion, a combination of arterial and NT SVGs will continue to be the optimal strategy in the future treatment of most CABG patients and the NT SVG as the rst choice in sequential graing of target coronaries. Academic rivalry is not always in the interest of the patient and future cooperation is the path for optimizing the treatment of ischaemic heart disease.

giving the fact that a CABG operation is one of the most common operations in the world. ere is still debate about the best secondchoice conduit to bypass the LAD. An improved SVG could simplify a complex CABG procedure if the patency was improved. With this background, a study was launched examining gra patency in 91 CABG patients at a mean time of 6years postoperatively. ese patients had received at least one NT SVG to the LAD artery. e NT SVG to the LAD and other target coronaries showed a patency of

95.6% and 93.8% respectively. us, in elderly patients with multiple comorbidities, the NT SVG was suggested as a promising substitute to bypass the LAD artery.

European Society ofCardiology and European Association forCardio- ThoracicSurgery

Aer almost 30years of practice and research, the NT SVG was recommended in 2018 by the European Society of Cardiology and European Association for Cardio- oracic Surgery to be used in open harvesting of the saphenous vein. is comes aer multiple randomized trials showing superior patency rates of greater than 80% aer 16years.

Future aspects andchallenges

e NT technique has encountered several challenges over the years. e short learning curve is crucial to overcome and improved efciency with experience is the norm. Concerns have been raised about the issue of increased wound complications. Good preparation preoperatively is a key factor in reducing some of these concerns, namely mapping of the saphenous vein with ultrasonographic imaging to assess the quality and size of the vein, as well as marking

REFERENCES

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