Arterial Conduits in CABG

1. Arterial Conduits in CABG Ayman Abdul-Ghani June 2003 CTC - Liverpool

2. 35 - yr history of CABG. • Better outcome with technical refinements, myocardial protection and search for better conduits.

3. Vein grafts: • Early post-operative events: • Thrombosis • Hypercoagulable state • Technical reasons • upto 2.5 yras post op: Intimal Hyperplasia • 3 years or more: Atherosclerotic • Post-op antiplatelets/lipid lowering agents.

4. Why Arterial Patency is better: • Vasoconstrictor effects of leukotrienes less effective in IMA compared to SVG. • Antithrombotic properties of vein graft endothelium less well developed than in arterial grafts - less secretion of NO and PGI-2 by vein graft endothelium • Intimal proliferation • Graft-coronary discrepancy - eg.smaller proximal diameter, stasis + clot.

5. Other Alternative veins: • Lesser Saphenous vein: acceptable in 70%,difficult to harvest,many valves,concomitant sinus dilatations that disrupts laminar flow, lots of branches, anecdotal results on long term patency. • Brachial vein,cephalic,basilic:arm veins are small and thin walled, difficult to use, abnormal due to previous iv,prone to aneurysmal dilatation,segmental stenosis-1 yr patency 57%-66%, 6 yr 10%

6. Umbilical Vein:Gluteraldehyde-prepared, off the shelf, difficult to contour around the heart, 1 yr patency 50%. • Cryopreserved allograft sahenous veins:off the shelf 1-4 yr patency 15-47%,last resort, life saving procedures, to be replaced.

7. Arterial Grafts: • Intimal Hyperplasia and atherosclerosis RARE. • Long term failure is usually due to progressive athersosclerosis in CA.

8. ITA: • Gold Standard. • Superiority of ITA to LAD disclosed in 1986 - Loop and colleagues from the Cleveland Clinic. • Lytle and associates: Two ITA grafts are better than one.

9. ITA: • Resistant to atherosclerosis (well formed internal elastic lamina, perivascular lymphatic drainage,fewer muscle cells in the media, biochemical differences compared with SVG. • 3% are atherosclerotic at origin. • Use of papaverine !

10. ITA: • Longer operative time, post-op bleeding,sternal healing with bilateral use. • Uncommon problems: steal from proximal branches, atherosclerosis, fistulization to the lung, severe tortuosity and atherosclerosis. • Currently Best graft available.

11. Radial artery: • First used for CABG by Carpentier & associates 1973. • Abandoned soon due to strong tendency to spasm. • Revived in 1990’s by Acar & colleagues with the use of Ca channel blockers.

12. Radial artery: • Thicker wall than ITA. • Ideal diameter. • Rarely affected by atherosclerosis. • When to use it ? • Contraindiction: positive Allen’s test. • Others: Raynaud’s,Buerger’s disease, subclavian bruit, planned AV fistula.

13. Radial artery: • Long term patency results. • Use of Calcium channel blockers. • Harvest/ enblock with fat and concomitant veins, temporary occlusion proximally, stump pressure measurement !

14. The Allen Test: • 1929. • Thromboangiitis obliterans. • 6% UA originates from RA. • 3% incomplete deep palmar arch. • 53% incomplete superficial palmar arch. • 1% significant loss to SPA, 3% significant loss to DPA with sacrifice of RA.

15. The Allen Test: • 1929. • Thromboangiitis obliterans. • 6% UA originates from RA. • 3% incomplete deep palmar arch. • 53% incomplete superficial palmar arch. • 1% significant loss to SPA, 3% significant loss to DPA with sacrifice of RA.

16. Right Gastroepiploic artery: • Early 1980’s. • Lumen-to-outer media distance is slightly less than ITA. • Less elastic tissue. • Fewer smooth muscle cells in media. • Initially strict indications: no other conduit available, now used more. • Propensity to spasm. In vitro studies, rings develop three times the force of ITA.

17. Right Gastroepiploic artery: • Too small for use as a bypass graft in only 1.4 % in USA. • Contraindications: previous gastric resection, morbid obesity, atherosclerosis of the descending aorta and celiac axis. • Harvest is time consuming, Emergency ! • Long term patency ! • Calcium Channel blockers start in theatre !

18. Right Gastroepiploic artery: • Atherosclerosis is rare. • Difficult to angio, spasm ! • Use: avoid BIMA, near occlusion to RCA or PDA, anastomosis of SVG to GEA in calcified ascending aorta (no touch tech.). • Correct orientation.

19. Inferior epigastric Artery: • Harvest: different side of ITA. • Athersclerosis near orifice of IEA in small percentage. • Patency rate: 57-86% at 25 months. • Patch of pericardium or SV at proximal end improved patency. • Decreased patency with small coronaries, not to use in DG or small OM • Better patency reported with anastomses to ITA pedicle

20. Splenic artery: • Used in early years of CABG. • Patency 1-2 yr reported up to 90%. • Very difficult to harvest, tortuosity. • 42% evidence of atherosclerosis in vessel wall. • Significant incidence of pancreatitis.

21. Left gastric artery: • Three cases reported by one surgeon.

22. Lateral costal artery: • Found in 27% of cadavers. • Traverses 6 intercostal spaces. • Originates from ITA,SCA or supreme ICA. • Histologically identical to ITA. • Can be used as free or pedicled graft.

23. Subscapular artery: • Origin: axillary artery. • Bifurcates to thoracodorsal and circumflex scapular arteries. • Can be dissected in Lt. Thoracotomies for re-do CABG. • Used as free graft from descending aorta to CA. • 8% have atherosclerotic disease. • Few reported cases.

24. Other grafts: • Dacron: no new intima formation, thrombogenic. • PTFE - Perma flow graft: 32% patency at 2 years, Aorta-SVC fistula. Diffuser-reducer cone at venous end, cautious optimism and pharmacologic agents.