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Exclusive internal mammary artery CABG: The nec plus ultra in myocardial revascularisation

An article from the E-Journal of the ESC Council for Cardiology Practice

Long-term results of myocardial revascularization (MR) using the internal thoracic artery (ITA) are superior to those reported with other grafts. Furthermore, it is possible to perform multiple vessel MR using exclusively both ITA in a Y fashion with multiple sequential coronary anastomoses. In triple-vessel diseased patients, this procedure offers coronary arterial tree reconstruction with superior long term graft patency and without increasing operative morbimortality.



1 - Improvement in interventional cardiology

Advances in percutaneous coronary intervention (PCI) have given this therapeutic option -exclusive internal mammary artery CABG - a key and irrevocable role in the management of CAD. There has been a considerable and steady increase in the number of PCI procedures, furthermore, the indications have spread to include triple vessel disease and left main stem lesions which were classically considered exclusive surgical territory.

Surgeons are thus confronted to performing more complex, multiple vessel coronary revascularisation after failure of PCI approach. Target arteries are often multistented or multistenosed with small calibre and poor run-off. Patients are also referred later to surgery with worsening symptoms and greater co-morbidities. Thus the challenge is to achieve complete revascularisation in an unfavourable setting with a greater risk of graft occlusion.

The bypass conduit is a dominant factor in the long-term follow-up of CABG. While the saphenous vein has been considered a predominant graft, venous graft atherosclerosis continues to be the major cause of late failure of CABG (1).

2 - The use of the internal thoracic artery

Parallel to improvement in interventional cardiology and progress from bare metal to drug eluting and biodegradable stents, surgical revascularisation of the myocardium has undergone major advances. Selection of the bypass graft with adequate flow and the greatest longevity is thus of vital importance and consequently the use of the internal thoracic artery (ITA) instead of saphenous vein grafts is preferred whenever possible. The ITA has demonstrated superior long-term clinical results after CABG compared to saphenous vein grafts with 85% to 95% freedom from significant stenosis at 7 to 10 years (2-5).  Moreover, the ITA outperforms other arterial grafts, namely the radial and gastroepiploic arteries, and is now undeniably the conduit of choice for surgical revascularisation.

The structure of the ITA is adapted to arterial pressures and high flow rates and produces greater amounts of relaxing factors namely nitric oxide providing a superior reactivity to flow requirements in the coronary arteries (6). Bypass of the left anterior descending (LAD) artery by the left ITA has been widely accepted as a major positive prognostic factor in patients undergoing CABG and has been standard for more than two decades (7-9).

The use of both ITA has demonstrated additional advantages over the use of single ITA in combination with vein grafts. Bilateral ITA grafting is an independent predictor of improved long-term survival and freedom from recurrence of angina, late myocardial infarction, reoperation, angioplasty and other cardiac-related events (5,10-13). This remains true when ITA is used as in-situ, sequential, or free graft (14,15). Purely ITA grafting for triple-vessel-diseased patients by connecting the free right ITA end-to-side to the in-situ left ITA as a Y graft has been reported with encouraging long term results (16,17).

3 - Description of the technique

The technique consists of complete extra-pleural skeletonised harvesting of both ITA. The fascia is peeled off the ITA while the internal thoracic veins are left in-situ to preserve a certain degree of vascularisation of the sternum. The right ITA is divided at its origin and connected end-to-side to the in-situ left ITA in a Y fashion (ITA-Y anastomosis, figure 1).

The left ITA is generally used to bypass the anterior coronary arteries (LAD, diagonal and ramus intermedius) and the right ITA to the lateral and inferior coronary arteries of the heart (ramus intermedius, obtuse marginal, posterior descending and right posterolateral) in a sequential fashion (figure 2).

Clinical results of the ITA-Y and sequential side-to-side ITA-coronary anastomoses have been inferred from clinical signs and cardiac functional assessments (scintigraphy, exercise ECG, …etc) but their patency has also been evaluated by direct graft visualisation (coronary angiography and CT angioscan) (18). Furthermore, similar patency rates of LITA and RITA connected to the same coronary arteries regardless of the targeted coronary artery or whether they are used in-situ or as free grafts have been reported (19-21).

Figure 1 : End-to-side anastomosis of the right ITA on the in-situ left ITA in a Y fashion

 



















Figure 2
: In the schematic representation, the left ITA is used to bypass the anterior coronary (LAD and diagonal) arteries and the right ITA to the lateral and inferior coronary (obtuse marginal and posterior descending) arteries of the heart in a sequential fashion 

Conclusion:

Exclusive internal thoracic artery bypass is reproducible and safe to perform routinely. Although more demanding technically, this procedure allows arterial reconstruction of the coronary tree without increasing the postoperative morbidity and mortality, providing complete myocardial revascularisation in triple-vessel-diseased patients with an excellent quality of anastomoses and outcome. 

References


1- Fitzgibbon GM, Kafka HP, Leach AJ, Keon WJ, Hooper GD, Burton JR. Coronary bypass graft fate and patient outcome: angiographic follow-up of 5,065 grafts related to survival and reoperation in 1,388 patients during 25 years. J Am Coll Cardiol. 1996;28:616-26.

2- Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K, Taylor PC. Long-term (5 to 12 years) serial studies of internal mammary artery and saphenous vein coronary bypass grafts. J Thorac Cardiovasc Surg. 1985;89:248-58.

3- Cameron A, Davis KB, Green G, Schaff HV. Coronary bypass surgery with internal-artery-grafts—effects on survival over 15 year period. N Engl J Med. 1996; 334: 216–219.

4- Barner HB, Barnett MG. Fifteen- to twenty-one-year angiographic assessment of internal thoracic artery as a bypass conduit. Ann Thorac Surg.  1994; 57: 1526–1528.

5- He GW. Arterial grafts for coronary artery bypass grafting: biological characteristics, functional classification, and clinical choice. Ann Thorac Surg. 1999; 67: 277–284.

6- Luscher TF, Diederich D, Siebenmann R, Lehmann K, Stulz P, von Segesser L, Yang ZH, Turina M, Gradel E, Weber E, et al. Difference between endothelium-dependent relaxation in arterial and in venous coronary bypass grafts. N Engl J Med. 1988; 319: 462–467.

7- Cameron A, Davis KB, Green GE, Schaff HV. Coronary bypass surgery with internal-thoracic-artery grafts: effects on survival over a 15-year period. N Engl J Med. 1996;334: 216–219.

8- Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal-mammary-artery graft on 10-year survival and other cardiac events. N Engl J Med. 1986; 314: 1–6.

9- Zeff RH, Kongtahworn C, Iannone LA, et al. Internal mammary artery versus saphenous vein graft to the left anterior descending coronary artery: prospective randomized study with 10-years follow-up. Ann Thorac Surg. 1988; 45: 533–536.


10- Pick AW, Orszulak TA, Anderson BJ, Schaff HV. Single versus bilateral internal mammary artery grafts: 10-year outcome analysis. Ann Thorac Surg. 1997;64:599-605.

11-  Buxton BF, Komeda M, Fuller JA, Gordon I. Bilateral internal thoracic artery grafting may improve outcome of coronary artery surgery. Risk-adjusted survival. Circulation. 1998;98:II1-6.

12- Lytle BW, Blackstone EH, Loop FD, Houghtaling PL, Arnold JH, Akhrass R, McCarthy PM, Cosgrove DM. Two internal thoracic artery grafts are better than one. J Thorac Cardiovasc Surg. 1999;117:855-72.

13- Taggart DP, D'Amico R, Altman DG. Effect of arterial revascularization on survival: a systematic review of studies comparing bilateral and single internal mammary arteries. Lancet. 2001;358:870-5.

14- Dion R, Glineur D, Derouck D, Verhelst R, Noirhomme P, El Khoury G, Degrave E, Hanet C. Long-term clinical and angiographic follow-up of sequential internal thoracic artery grafting. Eur J Cardiothorac Surg. 2000;17:407-14.

15- Calafiore AM, Contini M, Vitolla G, Di Mauro M, Mazzei V, Teodori G, Di Giammarco G. Bilateral internal thoracic artery grafting: long-term clinical and angiographic results of in situ versus Y grafts. J Thorac Cardiovasc Surg. 2000;120:990-6.

16- Ascione R, Underwood MJ, Lloyd CT, Jeremy JY, Bryan AJ, Angelini GD. Clinical and angiographic outcome of different surgical strategies of bilateral internal mammary artery grafting. Ann Thorac Surg. 2001;72:959-65.

17- Tector AJ, McDonald ML, Kress DC, Downey FX, Schmahl TM. Purely internal thoracic artery grafts: outcomes. Ann Thorac Surg. 2001;72:450-5.

18- Nottin R, Grinda JM, Anidjar S, Folliguet T, Detroux M. Coronary-coronary bypass graft: an arterial conduit-sparing procedure. J Thorac Cardiovasc Surg. 1996;112:1223-30.

19- Azmoun A, Ramadan R, Al-Attar N, Kortas C, Ghostine S, Caussin C, Bourachot ML, Lancelin B, Slama M, Nottin R. Exclusive internal thoracic artery grafting in triple-vessel-disease patients: angiographic control. Ann Thorac Surg. 2007;83:2098-102.

20- Tatoulis J, Buxton BF, Fuller JA. Results of 1,454 free right internal thoracic artery-to-coronary artery grafts. Ann Thorac Surg. 1997;64:1263-8.

21- Tatoulis J, Buxton BF, Fuller JA. Patencies of 2127 arterial to coronary conduits over 15 years. Ann Thorac Surg. 2004;77:93-101.

22- Shah PJ, Durairaj M, Gordon I, Fuller J, Rosalion A, Seevanayagam S, Tatoulis J, Buxton BF. Factors affecting patency of internal thoracic artery graft: clinical and angiographic study in 1434 symptomatic patients operated between 1982 and 2002. Eur J Cardiovasc Surg. 2004;26:118-24.

23- Al-Attar N.  Coronary flow reserve in composite arterial Y grafts. Ann Thorac Surg. 2003;76:659-60.

VolumeNumber:

Vol7 N°37

Notes to editor


Prof Nawwar Al-Attar
Department of Cardiac Surgery, Bichat University Hospital, Paris, France

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.