condiuts in Coronary artery bypass grafting

Dr.Ramprasath

Arterial ConduitsAutologous Internal thoracic artery Right gastroepiploic artery Inferior epigastric artery Radial artery Splenic artery Gastroduodenal artery Left gastric artery Intercostal arteryNonautologous Bovine internal thoracic artery

Venous Conduits

Autologous Greater saphenous vein Short (lesser) saphenous vein Upper extremity veins (cephalic and

basilic)Nonautologous Umbilical vein Greater saphenous vein homografts

Conduit Options ?

How to decide about ? Life expectancy of individual? Elective or emergency? Age ? Target vessel in Angio ? Co-morbidities?

Cleeveland clinic study

Comparison of Saphenous Vein and Internal Thoracic Artery Graft Patency by Coronary System(1972-1999)

Joseph F. Sabik, III, MDa,*, Bruce W. Lytle, MDa, Eugene H. Blackstone, MDa,b, Penny L. Houghtaling, MSb, Delos M. Cosgrove, MDa

LIMA - 93%, 90%, and 88% 

GSV - 78%, 65%, and 57%

CONCLUSIONS: Internal thoracic arteries demonstrate better patency than saphenous veins except when grafting moderately stenosed right coronary arteries. When bypassing right coronary arteries with less than 70% stenosis, saphenous veins may be a better choice.

LIMA Patency 96.4% at 1 year, 89.1% at 5 years,

and 88% at 10 years.(The Journal of Thoracic and

Cardiovascular Surgery, Vol 90, 668-675,barner et al)

Angiographic patency of grafts

Conduit 1 yr 5 yr 10yr 15 yr

LIMA 99 95-98 85-95 88RIMA 98 95-98 80-85 65RA 96 79 67RGEA 95 63IEA 79GSVCurrent 80-95 73 55-75 32-

40Historic 80-95 75 45

2011 ACCF/AHA Guideline forCoronary Artery Bypass Graft Surgery Bypass Graft Conduit: Recommendations

CLASS I

1. If possible, the left internal mammary artery (LIMA) should be used

to bypass the left anterior descending (LAD) artery when bypass of the LAD artery is indicated . (Level of Evidence: B)

Journal of the American College of Cardiology Vol. 58, No. 24, 2011© 2011 by the American College of Cardiology Foundation and the American Heart Association, Inc. ISSN 0735-1097/$36.00Published by Elsevier Inc. doi:10.1016/j.jacc.2011.08.009

CLASS IIa1. The right internal mammary artery (IMA) is

probably indicated to bypass the LAD artery when the LIMA is

unavailable or unsuitable as a bypass conduit. (Level of Evidence: C)2. When anatomically and clinically suitable, use

of a second IMA to graft the left circumflex or right coronary

artery (when critically stenosed and perfusing LV myocardium) is

reasonable to improve the likelihood of survival and to decrease

reintervention . (Level of Evidence: B)

CLASS IIb1. Complete arterial revascularization may be

reasonable in patientsless than or equal to 60 years of age with few or no

comorbidities.(Level of Evidence: C)2. Arterial grafting of the right coronary artery may

be reasonable when a critical (90%) stenosis is present. (Level

of

Evidence: B)3. Use of a radial artery graft may be reasonable

when graftingleft-sided coronary arteries with severe stenoses

(70%) and rightsided arteries with critical stenoses (90%) that perfuse LV myocardium . (Level of Evidence: B)

CLASS III: HARM1. An arterial graft should not be used

to bypass the right coronary artery with less than a critical stenosis (90%)

Date of download: 1/29/2013

Copyright © The American College of Cardiology. All rights reserved.

From: Long-term patency of saphenous vein and left internal mammary artery grafts after coronary artery bypass surgery: Title and subTitle BreakResults from a Department of Veterans Affairs Cooperative Study

J Am Coll Cardiol. 2004;44(11):2149-2156. doi:10.1016/j.jacc.2004.08.064

Plot of time to development of 50% to 99% stenosis in internal mammary artery (IMA) and single saphenous vein graft (SVG) to the left anterior descending coronary artery (LAD). The number of patients at each time point is listed in the figure. *p < 0.001 (IMA vs. single SVG to LAD). CABG = coronary artery bypass grafting.

Figure Legend:

Date of download: 1/29/2013

Copyright © The American College of Cardiology. All rights reserved.

From: Long-term patency of saphenous vein and left internal mammary artery grafts after coronary artery bypass surgery: Title and subTitle BreakResults from a Department of Veterans Affairs Cooperative Study

J Am Coll Cardiol. 2004;44(11):2149-2156. doi:10.1016/j.jacc.2004.08.064

Plot of time-related graft patency (or freedom from graft occlusion) for saphenous vein grafts (SVG) to the left anterior descending (LAD), circumflex (CX), and right coronary (RCA) arteries. The number of patients at each time point is listed in the figure. *p < 0.001 (LAD vs. CX and/or RCA). CABG = coronary artery bypass grafting.

Figure Legend:

LIMA is Gold standard Radial is good GSV is acceptable Gastro-epiploic better to know Re-Do ???? conduit

LIMA

AnatomyOrigin: from the inferior aspect of

the first part of subclavian artery, opposite the thyrocervical trunk. This origin is 2cm above the sternal end of clavicle

Course: Above the first costal cartilage,

it runs downwards, forward and medially behind the sternal end of the clavicle

(Related posteriorly to subclavian vein, phrenic nerve)

Below the first costal cartilage, the artery runs vertically down upto its termination in the 6th IC space – 2 cm lateral to edge of sternum.

Terminates by dividing into the superior epigastric and musculophrenic arteries

Branches:1. Pericardiophrenic artery –

arises at the root of neck and accompanies the phrenic nerve. = supplies pericardium and pleura

2. Mediastinal arteries – irregular branches supply the thymus, mediastinal fat

3. Two anterior intercostal arteries per space in upper 6 spaces

4. Perforating branches to the anterior chest wall. In females 2,3,4 perforators supply the breast

5. Superior epigastric artery enters the rectus sheath at the 7th cartilage

6. Musculophrenic artery runs down and laterally behind the costal cartilages and gives anterior intercostal arteries.

RelationshipsAnteriorly – upper 6 costal cartilagesand the internal

intercostal muscles of the spaces

Posteriorly – sternocostalis muscle

Features of IMA suitable as coronary conduit1. Internal elastic laminae has fewer and smaller fenestrations

2. Muscular media has numerous elastic laminae

3. Media has fewer smooth muscle cells

4. Intact endothelium produces EDRF and prostacyclin

5. Arterial conduit – it is used to arterial pressures = lesser intimal hyperplasia

6. Live graft with vasa vasorum

7. Adaptabilty to increased flow demand

8. Pedicle graft – so no proximal anastamosis

9. Anatomical location – suitable for coronary grafting

10. Suitable diametre – 3.5 mm matches coronary

11. Wont be missed - Anterior chest wall has numerous collateral blood supply

The histology of the ITA lined with typical arterial

endothelium Internal elastic lamina has fewer

and smaller fenestrations.

The media is between the internal and external elastic laminae - contains fewer smooth muscle cells and 5-9 elastic lamellae.

The proximal and distal 10 to 20 percent contains fewer lamellae, and usually none are distal to the bifurcation.

The adventitia contains dense collagen fibers and transits to loose alveolar tissue that contains vasa vasorum that do not penetrate the media.

Wall thickness is about 200 µm, which is well under the 350 µm that can be nourished by diffusion from the lumen.

The elastin layers appear black, muscle is red and collagen blue.

EDRFEndothelium derived relaxing factor (EDRF = Nitric oxide)

The ITA endothelium releases more prostaglandin I2 (prostacyclin) and shows greater NO-mediated vasodilation than does saphenous vein.

Extraluminal release of NO causes relaxation of vascular smooth muscle.

Intraluminal NO inhibits platelet aggregation and adhesion and promotes platelet disaggregation as well.

Downstream travel of NO from the ITA may cause coronary vasodilation.

Because NO inhibits mitogenesis and smooth muscle proliferation, the chemical may inhibit development of atherosclerosis in the ITA.

Activated neutrophils cause more vasoconstriction in saphenous vein than in the ITA.

Histamine is a potent stimulus for NO release. Serotonin-induced vasoconstriction is inhibited by NO.

from platelets, mast cells, and endothelium - implicated in coronary spasm, may contribute to venous graft spasm

but are unlikely to cause ITA spasm

Harvesting

Intra-thoracic ,Extra thoracic Along with tissue or skeletionised Methods to overcome spasm? Papaverine in blood or saline? 1 to 2 mg/ml- extraluminal 0 .5 mg/ml- intraluminal Avoid hydrostatic dilatation

Grafting strategy

LIMALAD LIMA LCX ,RIMA LAD Use as Free graft when damaged Flow should be good (30-150 ml/min) Diseased aorta- svg hood or

pericardial patch

Presumed difficulty of Dissection Fragility of the ITA, limitations of flow through the

arterial conduit, and Restricted versatility.

Caution regarding the use of the internal mammary artery:

1) Diabetics, Immunocompromised and CRF 2) Extremely old patients (life expectancy <10yrs)-

most likely not benefit. 3) Atherosclerotic subclavian arteries. 4) Patients requiring emergency surgery for

cardiogenic shock- increased time 5) Severely calcified or extremely tiny target

coronary artery would minimally benefit 6) Heavy dose radiation to chest

One of the major problems with IMA grafts is – chance of spasm in the perioperative period which can result in acute infarction.

Patency LIMA to LAD = 92 to 97 percent at 1 year,

88 to 96 percent at 5 years

88 to 93 percent at 10 years.

Right ITA patency is less by 5 to 10 percent(but if only grafts to the LAD are considered, patency is comparable for

the two conduits)

The failure rate for ITA grafts is 0.5 to 1.0 percent per year between years 1 and 10. Beyond the tenth year only anecdotal data are available.

Data from: Loop FD, Lytle BW, Cosgrove DM, et al, N Engl J Med 1986; 314:1.

FACTORS INFLUENCING CONDUIT PATENCY Intimal fracturing and thrombosis, Profound spasm with secondary

thrombosis, Faulty anastomotic technique, severe coronary disease, and competitive coronary flow causing

thrombosis

Radial artery

Radial Artery

1973, Carpentier yielded encouraging results with 90% patency at 1 to 10 months.

Curtis et al of the radial artery grafts Studied between 7 and 19 days postoperatively were patent, only 26% of the grafts were patent at 2 to 12 months after operation.

Fisk et al who found that of the 48 radial artery grafts studied after 1 to 24 weeks, 50% were not patent, whereas simultaneously placed GSV grafts had a patency rate of 77%.

Radial artery

Muscular media thicker & devoid of elastic fibres Check for completeness of arch

Papaverine ,low dose milirinone short term amlodipine (possati et al 2003,108.1350-4) ? Benefit of diltiazem

Grafting strategy- Y graft, T Graft, vein hood

Patency 5 year – 78%-96% 10 year- 88 % Compititive coronary flow – 80%

stenosis is cut-off , better if 90 % stenosed target.

Ann Thorac Surg 2002;73:143-148The radial artery in coronary surgery: a 5-year experience—clinical and angiographic results,6446 patients

James Tatoulis, FRACS*a, Alistair G. Royse, FRACSa, Brian F. Buxton, FRACSa, John A. Fuller,

FRACPa, Peter D. Skillington, FRACSa,John C. Goldblatt, FRACSa, Robin P. Brown, FRACSa, Michael A. Rowland, FRACSa

Right Gastroepiploic artery Histology similar to Radial Less atherosclerosis Cruciate incision in diaphragm

Perrault et al with 51 right gastroepiploic in situ grafts with a patency rate of 90% in 31 patients prior to hospital discharge.At 1 year- 80% .

Mills et al showed 82% patency at 11 months .

Suma et al 10 year patency 87%

In Re-do surgery when no other option it can be an alternative

Great saphenous vein

Media is composed of smooth muscle cells

Wall is too thick for intraluminal nutrition

Devoid of vasavasorum SM death replaced by fibrosis after few years its rigid tube

NO production by native endothelium is less more so if regenerated

Patency 1 year- 80-90% 5 year- 70% 10 year- 40- 60 % 15 year- 32%

Technical issues to improve patency Mark the vein

Minimal handling Harvest with pad of fat Don`t divide until its

needed Distension with blood

better

Try to maintain lumen uniformity

Adequate anastamosis Try to match the proximal and distal

calibre while anastamosing ( > 50% diffrence not good)

Postoperative Antiplatelet Therapy:Recommendations CLASS I If aspirin (100 mg to 325 mg daily) was

not initiated preoperatively, it should be initiated within 6 hours postoperatively and then continued indefinitely to reduce the occurrence of SVG closure and adverse cardiovascular events . (Level of Evidence: A)

CLASS IIa For patients undergoing CABG,

clopidogrel 75 mg daily is a reasonable alternative in patients who are intolerant of or allergic to aspirin. (Level of Evidence: C)

Future-eSVS mesh

Other alternatives

Cephalic vein Inferior epigastric

Patency Assessment confounded certain facts: (1) alternative conduits are

used only in circumstances in which the ITAs and GSVs are unavailable;

(2) used in the least favorable site

(3) there is a lack of uniformity in obtaining long-termfollow-up angiograms to determine the reliable patency rates for each alternative conduit; and

(4) it is possible that surgeons are as unfamiliar with the use of alternative conduits as they are with theITA and GSV.

NEW STRATEGIES TO IMPROVE GRAFT PATENCY Transfer of the endothelial-type nitric

oxide

synthase gene Fibroblast growth factor- inside PTFE Therapeutic angiogenesis

Conclusion

In the usual clinical cardiac surgery practice, if one becomes familiar with the expanded use of the ITAs,lower extremity veins, and possibly right gastroepiploic artery, the other conduits are rarely needed.

Think of future Re-do ,conserve conduits

In the future, the search for an ideal coronary bypass conduit"off the shelf`` will continue to evolve.

Thank you….