External support

In cardiac surgery and vascular surgery, external support (or external stent) is a type of scaffold made of metal or plastic material that is inserted over the outside of the vein graft in order to decrease the intermediate and late vein graft failure after bypass surgery (e.g. CABG).

Venous external support made of cobalt chromium alloy mesh.

An external support (external stent) should be differentiated from a stent. An external support is placed on the outside of the vessel whereas a stent is inserted into the lumen of a vessel.

Background

Veins are adapted to an environment of low pressure and low flow. In order to bypass the coronary obstruction and restore blood flow, veins are transferred and integrated into the arterial circulation, where they exposed to high pressure and flow. These new hemodynamic conditions cause intimal hyperplasia and atherosclerosis that cause intermediate and late vein graft failure.[1][2] The idea of placing an external support on the vein graft was first suggested in 1963.[3] The rational being that it will diminish the circumferential strain of the graft wall, therefore inhibiting intimal hyperplasia and later superimposed atherosclerosis, aiding with the adaptation of the vein toward the arterial environment.

Method

The external scaffold provides a mechanical support for the vein graft, absorbs the high arterial pressure, constrict the vein graft dilatation, reduces lumen irregularities and mitigates intimal hyperplasia formation. As shown both in human tissue cultures and experimental models.[4][5][6][7][8] However, until recently there were a limited number of clinical studies that showed less positive results.[9][10][11] It was hypothesized that graft patency rates were lower with external support, because of aggressive over constriction of the vein graft, unsuitable material of the devices and the use of fibrin glue that has shown to cause tissue damage, fibrosis and intimal hyperplasia.[12][13][14] Lately, more promising results with second generation devices showed that external support can mitigate intimal hyperplasia development, improve vein graft lumen uniformity and improve the flow pattern inside the graft.[15][16][17][18] These benefits shown to remain for up to five years follow up.[19] In addition to improving the vein graft failure rates in bypass surgeries, other research studies showed that external support might allow the use of conduits that previously have been considered to be unsuitable for surgery.[20][21]

To date the technique is practiced in several cardiac centers in Europe, Israel and South Africa. Further clinical studies are ongoing in Europe and the US on a larger number of patients.[22][23][24]

References
  1. Harskamp, RE; Lopes, RD; Baisden, CE; de Winter, RJ; Alexander, JH (May 2013). "Saphenous vein graft failure after coronary artery bypass surgery: pathophysiology, management, and future directions". Annals of Surgery. 257 (5): 824–33. doi:10.1097/SLA.0b013e318288c38d. PMID 23574989. S2CID 45552165.
  2. Motwani, JG; Topol, EJ (10 March 1998). "Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention". Circulation. 97 (9): 916–31. doi:10.1161/01.CIR.97.9.916. PMID 9521341.
  3. PARSONNET, V; LARI, AA; SHAH, IH (October 1963). "New Stent for Support of Veins in Arterial Grafts". Archives of Surgery. 87 (4): 696–702. doi:10.1001/archsurg.1963.01310160158031. PMID 14056256.
  4. Izzat, MB; Mehta, D; Bryan, AJ; Reeves, B; Newby, AC; Angelini, GD (1 October 1996). "Influence of external stent size on early medial and neointimal thickening in a pig model of saphenous vein bypass grafting". Circulation. 94 (7): 1741–5. doi:10.1161/01.CIR.94.7.1741. PMID 8840869.
  5. Angelini, GD; Lloyd, C; Bush, R; Johnson, J; Newby, AC (November 2002). "An external, oversized, porous polyester stent reduces vein graft neointima formation, cholesterol concentration, and vascular cell adhesion molecule 1 expression in cholesterol-fed pigs". The Journal of Thoracic and Cardiovascular Surgery. 124 (5): 950–6. doi:10.1067/mtc.2002.127004. PMID 12407378.
  6. Lardenoye, JH; De Vries, MR; Grimbergen, JM; Havekes, LM; Knaapen, MW; Kockx, MM; van Hinsbergh, VW; van Bockel, JH; Quax, PH (1 September 2002). "Inhibition of accelerated atherosclerosis in vein grafts by placement of external stent in apoE*3-Leiden transgenic mice". Arteriosclerosis, Thrombosis, and Vascular Biology. 22 (9): 1433–8. doi:10.1161/01.ATV.0000030339.79524.6E. PMID 12231562.
  7. Moodley, L; Franz, T; Human, P; Wolf, MF; Bezuidenhout, D; Scherman, J; Zilla, P (July 2013). "Protective constriction of coronary vein grafts with knitted nitinol". European Journal of Cardio-Thoracic Surgery. 44 (1): 64–71. doi:10.1093/ejcts/ezs670. PMC 3708718. PMID 23295444.
  8. Longchamp, A; Alonso, F; Dubuis, C; Allagnat, F; Berard, X; Meda, P; Saucy, F; Corpataux, JM; Déglise, S; Haefliger, JA (March 2014). "The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins". Biomaterials. 35 (9): 2588–99. doi:10.1016/j.biomaterials.2013.12.041. PMID 24429385.
  9. Murphy, GJ; Newby, AC; Jeremy, JY; Baumbach, A; Angelini, GD (August 2007). "A randomized trial of an external Dacron sheath for the prevention of vein graft disease: the Extent study". The Journal of Thoracic and Cardiovascular Surgery. 134 (2): 504–5. doi:10.1016/j.jtcvs.2007.01.092. PMID 17662798.
  10. Schoettler, J; Jussli-Melchers, J; Grothusen, C; Stracke, L; Schoeneich, F; Stohn, S; Hoffmann, G; Cremer, J (October 2011). "Highly flexible nitinol mesh to encase aortocoronary saphenous vein grafts: first clinical experiences and angiographic results nine months postoperatively". Interactive Cardiovascular and Thoracic Surgery. 13 (4): 396–400. doi:10.1510/icvts.2010.265116. PMID 21724659.
  11. Emery, RW; Solien, E; Klima, U (2014). "Clinical evaluation of the eSVS Mesh: First-in-Man trial outcomes". ASAIO Journal. 61 (2): 178–83. doi:10.1097/MAT.0000000000000187. PMID 25493460. S2CID 23333421.
  12. de Vries, MR; Simons, KH; Jukema, JW; Braun, J; Quax, PH (August 2016). "Vein graft failure: from pathophysiology to clinical outcomes". Nature Reviews. Cardiology. 13 (8): 451–70. doi:10.1038/nrcardio.2016.76. PMID 27194091. S2CID 10771813.
  13. Mawhinney, Jamie A; Mounsey, Craig A; Taggart, David P (8 December 2017). "The potential role of external venous supports in coronary artery bypass graft surgery†". European Journal of Cardio-Thoracic Surgery. 53 (6): 1127–1134. doi:10.1093/ejcts/ezx432. PMID 29228235.
  14. Stojanovic, Tomislav; El-Sayed Ahmad, Ali; Didilis, Vasilios; Ali, Osama; Popov, Aron F.; Danner, Bernd C.; Seipelt, Ralf; Dörge, Hilmar; Schöndube, Friedrich A. (29 May 2008). "Extravascular perivenous fibrin support leads to aneurysmal degeneration and intimal hyperplasia in arterialized vein grafts in the rat". Langenbeck's Archives of Surgery. 394 (2): 357–362. doi:10.1007/s00423-008-0341-3. PMID 18509670.
  15. Taggart, DP; Ben Gal, Y; Lees, B; Patel, N; Webb, C; Rehman, SM; Desouza, A; Yadav, R; De Robertis, F; Dalby, M; Banning, A; Channon, KM; Di Mario, C; Orion, E (June 2015). "A Randomized Trial of External Stenting for Saphenous Vein Grafts in Coronary Artery Bypass Grafting" (PDF). The Annals of Thoracic Surgery. 99 (6): 2039–45. doi:10.1016/j.athoracsur.2015.01.060. hdl:10044/1/53822. PMID 25886810. S2CID 25323596.
  16. Taggart, DP; Amin, S; Djordjevic, J; Oikonomou, EK; Thomas, S; Kampoli, AM; Sabharwal, N; Antoniades, C; Krasopoulos, G (1 May 2017). "A prospective study of external stenting of saphenous vein grafts to the right coronary artery: the VEST II study". European Journal of Cardio-Thoracic Surgery. 51 (5): 952–958. doi:10.1093/ejcts/ezw438. PMID 28379404.
  17. Webb, CM; Orion, E; Taggart, DP; Channon, KM; Di Mario, C (November 2016). "OCT imaging of aorto-coronary vein graft pathology modified by external stenting: 1-year post-surgery". European Heart Journal - Cardiovascular Imaging. 17 (11): 1290–1295. doi:10.1093/ehjci/jev310. PMID 26628615.
  18. "Vascular Graft Solutions' Improvements in Bypass Surgery Outcomes -". 6 January 2017.
  19. Taggart, DP; Webb, CM; Desouza, A; Yadav, R; Channon, KM; De Robertis, F; Di Mario, C (19 November 2018). "Long-term performance of an external stent for saphenous vein grafts: the VEST IV trial". Journal of Cardiothoracic Surgery. 13 (1): 117. doi:10.1186/s13019-018-0803-9. PMC 6245530. PMID 30453984.
  20. Zurbrügg, HR; Hetzer, R (December 1996). "The use of biocompound-grafts together with varicose veins. First clinical experience". The Journal of Cardiovascular Surgery. 37 (6 Suppl 1): 143–6. PMID 10064367.
  21. Zurbrügg, HR; Knollmann, F; Musci, M; Wied, M; Bauer, M; Chavez, T; Krukenberg, A; Hetzer, R (November 2000). "The biocompound method in coronary artery bypass operations: surgical technique and 3-year patency". The Annals of Thoracic Surgery. 70 (5): 1536–40. doi:10.1016/S0003-4975(00)01997-4. PMID 11093483.
  22. Head, Stuart J.; Milojevic, Milan; Taggart, David P.; Puskas, John D. (2 October 2017). "Current Practice of State-of-the-Art Surgical Coronary Revascularization". Circulation. 136 (14): 1331–1345. doi:10.1161/CIRCULATIONAHA.116.022572. PMID 28972063.
  23. "VEST III PMS Clinical Protocol - Full Text View - ClinicalTrials.gov".
  24. "VEST Venous Graft External Support Pivotal Study - Full Text View - ClinicalTrials.gov". 31 March 2021.
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