Stenotic coronary astery disease (CAD) is caused by the thickening and nal~owing of tlie coronary arteries (Atheri>sclerosis). lnitially it causes chest paill on effort (stable angina) and progression of the disease 1-esults in unstable angi~iil or myocardial infarction (MI). The modalities of trcntxnent arc medical,percutaneous invasive pwcedures (PCI) like angioplasty, stenting and operativt:procedure like coronary artcsy bypass surgery (CABG). Surgcry involves usage of a proper durable conduit to bypass blocks in coronary arteries.
Conduits
Venous Conduits
Reversed saphenous vein was the first conduit used for CABG. 'It is usually harvested from the leg starting above the ankle going up to a desired length. It could also be harvested from the thigh. Either a single, long skin incision or multiple skin incisions are made. The branches are ligated. The vein is removed and distended with heparinised blood or a solution containing glyceryl trinitrate(GTN) .
Arterial Conduits
Conduits
Venous Conduits
Reversed saphenous vein was the first conduit used for CABG. 'It is usually harvested from the leg starting above the ankle going up to a desired length. It could also be harvested from the thigh. Either a single, long skin incision or multiple skin incisions are made. The branches are ligated. The vein is removed and distended with heparinised blood or a solution containing glyceryl trinitrate(GTN) .
Arterial Conduits
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| Arterial conduits |
Internal Mamnrary Artery (IMA)
The intenla1 mammary arteries a i s e from the first pcuL of subclavintl artery and courses one cm lateral to the sternal edge on either side. In the sixth intercostal space it divided into two branches. It is accotnpanied by two venae comitantes. IMA is an ideal conduit for CABG because (I) size matches the coronary arteries, (2) resistant to atherosclerosis, and (3) has excellent long-
term patency rate.
Left internal inununary artery (LIMA): It is most often used for bypassing left anterior descending (LAD) coronary artery and its diagonal branch. The right internal maintnay artery (RIMA) is used for bypassiilg right coronary artery (RCA) or its posterior descending branch (PDA). IMA can be used as in silu grafi without disconnecting it from the subclavian artery, It can also be used
as a free graft between aorta and the coronay artery. For total arterial re-vascularisation (TAR) using msunmcvy arteries, free RIMA end is anastomosed to the side of LIMA as Y or T graft. The LIMA is then used for bypassing diagonal and LAD branches. RIMA is then taken around the he@ for side-to-side anastomoses with obtuse marginal branches (OM) and its end is anastomosed to PDA, thereby achieving total arterial re-vascularisation(TAR). In the place of RIMA a radial artery graft can be used the same way for total arterial re-vasculru-isation (TAR).Csrdiovascul:~r Surgery LIMA -Radial 'Y' grafi sequential to OM,, OM, & PDA
The intenla1 mammary arteries a i s e from the first pcuL of subclavintl artery and courses one cm lateral to the sternal edge on either side. In the sixth intercostal space it divided into two branches. It is accotnpanied by two venae comitantes. IMA is an ideal conduit for CABG because (I) size matches the coronary arteries, (2) resistant to atherosclerosis, and (3) has excellent long-
term patency rate.
Left internal inununary artery (LIMA): It is most often used for bypassing left anterior descending (LAD) coronary artery and its diagonal branch. The right internal maintnay artery (RIMA) is used for bypassiilg right coronary artery (RCA) or its posterior descending branch (PDA). IMA can be used as in silu grafi without disconnecting it from the subclavian artery, It can also be used
as a free graft between aorta and the coronay artery. For total arterial re-vascularisation (TAR) using msunmcvy arteries, free RIMA end is anastomosed to the side of LIMA as Y or T graft. The LIMA is then used for bypassing diagonal and LAD branches. RIMA is then taken around the he@ for side-to-side anastomoses with obtuse marginal branches (OM) and its end is anastomosed to PDA, thereby achieving total arterial re-vascularisation(TAR). In the place of RIMA a radial artery graft can be used the same way for total arterial re-vasculru-isation (TAR).Csrdiovascul:~r Surgery LIMA -Radial 'Y' grafi sequential to OM,, OM, & PDA
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| Coronary artery bypass grafting -Total arteri:rl re-vuscularisution |
The internal lnalnrriary artery is harvested as a pedicle with its vcnae con~itantes, nerve bundles and parts of inter costal muscles. It can also be skeleto~iised leaving only the al-tery. All the branches arc clipped with haemoclips. After median stemotomy a special retmctor is used to raise the sternal edge and the mammary artery is harvested. At thc upper end, care is taken not to injure phrenic nerve and subclavian vein while dissection is being done with electro caulery. The artery is sprayed with papavcrine solution (2 mn~olllitrc).
The distal end is divided and flow checked. The conduit is covered with gauze soaked in papaverine solution.Carpentier used radial aartc14y us a conduit for CABG in 197 1. He had 30 per cent early occlusion of the graft and it was given up. The mail1 p~.oblcm was radial a~-teiial spasnl. C.Acm in 90's re-introduced radial artely grafting after using 1.V diltiazem to cwercomc merial spasm. Radial artery is taken from the non-dorninant hand after performing Allen's test to cnsure ulnar artery's adequacy lo support palinar arch circulation. Doppler test can also be uscd for the same purgosc. It is hnrvcstcd by a long incision overlying the course of the artery. To avoid spasm pnpavcrine (30 mg / 20 1111 of saline) is liberally applied at the time of dissection and latcr on conduit is dipped in the sanlc solution until it is used. Patient is kept on 1.V diltiaze~n and later on oral dose up to six months.
Other Arterial Conduits
Gastro Epiploic Artery (GE)
Gastro epiploic artery is a less popular arterial conduit now. The midline chest incision is extended to the umbilicus and the right gastro epiploic artery along with its venae cornitantes is raised. The pedicle is passed behind duodenum and through the diaphragm. It is then used to bypass RCA, PDA or OM branches.
Inferior Epigastric Artery ( IEA )
This is a branch of external iliac artery supplying the abdominal wall. It is raised as a free graft for CABG. The usual length available is 6-8 cms.
Other Conduits
Synthetic Conduits
Dacron, Polytetra fluro ethylene (PTFE) and polyglycolic acid grafts have extremely poor results and are not used any more.Biological Conduits Freeze dried arterial, bovine M A , human umbilical vein, cry0 preserved umbilical vein or artery and ornnitlow sheep collagen tube grafts also have poor short and long term patency.
Longevity of Conduits (Long Term Patency)
Veirt Grafts
At the end of ten years only 50 per cent of saphenous vein grafts are patent and 50 per cent of the rest may have significant atherosclerotic changes. In a large series 93 per cent of the grafts were patent at 5 years, 54 per cent at 10 years and 16 per cent at 15 years. To a certain extent patency depends on the atraurnatic handling at the time of harvesting. Strict control of risk factors for development of atherosclerosis will also improve long-term patency of venous grafts.
Internal Mammary Artery (IMA)
This is an excellent graft. When left internal mammary artery (LIMA) is anastomosed to LAD, which has more than 70 per cent block, patency at the end of two years is 99 per cent. It falls to 92 per cent at the end of ten years.The right internal mammary artery (RIMA) can be used in situ to bypa~s RCA, PDA or LAD. It can also be used as a free graft with proximal end anastomosed Lo aorta or left internal mammary artery (LIMA) as a T or Y graft. Long-term patency of free IMA is slightly lower than in silu IMA. In
another large series IMA patency was 90 per cent at ten years. After ten years there was no further fall when followed up to twenty years. Inlernal mammary artery is particularly resistant to athero sclerosis.
Radial Ahery (RA)
Patency of RA is less than that of Ih4.A but much superior to a venous graft.One of the studies showed 90 per cent patency at 13 months and 83 per cent at the end of seven years. LIMA patency was 91 per cent for the same period.
ICarriiovascular Surgery
GEA is seldom used now. Patency has been reported as 94 per cent at one year, 88 per cent at five years and 83 per cell1 at ten years.
Inferior Epigastric Artery IEA is also not used frequently these days. Rcported patency is 93 per ccnt at five years.
The distal end is divided and flow checked. The conduit is covered with gauze soaked in papaverine solution.Carpentier used radial aartc14y us a conduit for CABG in 197 1. He had 30 per cent early occlusion of the graft and it was given up. The mail1 p~.oblcm was radial a~-teiial spasnl. C.Acm in 90's re-introduced radial artely grafting after using 1.V diltiazem to cwercomc merial spasm. Radial artery is taken from the non-dorninant hand after performing Allen's test to cnsure ulnar artery's adequacy lo support palinar arch circulation. Doppler test can also be uscd for the same purgosc. It is hnrvcstcd by a long incision overlying the course of the artery. To avoid spasm pnpavcrine (30 mg / 20 1111 of saline) is liberally applied at the time of dissection and latcr on conduit is dipped in the sanlc solution until it is used. Patient is kept on 1.V diltiaze~n and later on oral dose up to six months.
Other Arterial Conduits
Gastro Epiploic Artery (GE)
Gastro epiploic artery is a less popular arterial conduit now. The midline chest incision is extended to the umbilicus and the right gastro epiploic artery along with its venae cornitantes is raised. The pedicle is passed behind duodenum and through the diaphragm. It is then used to bypass RCA, PDA or OM branches.
Inferior Epigastric Artery ( IEA )
This is a branch of external iliac artery supplying the abdominal wall. It is raised as a free graft for CABG. The usual length available is 6-8 cms.
Other Conduits
Synthetic Conduits
Dacron, Polytetra fluro ethylene (PTFE) and polyglycolic acid grafts have extremely poor results and are not used any more.Biological Conduits Freeze dried arterial, bovine M A , human umbilical vein, cry0 preserved umbilical vein or artery and ornnitlow sheep collagen tube grafts also have poor short and long term patency.
Longevity of Conduits (Long Term Patency)
Veirt Grafts
At the end of ten years only 50 per cent of saphenous vein grafts are patent and 50 per cent of the rest may have significant atherosclerotic changes. In a large series 93 per cent of the grafts were patent at 5 years, 54 per cent at 10 years and 16 per cent at 15 years. To a certain extent patency depends on the atraurnatic handling at the time of harvesting. Strict control of risk factors for development of atherosclerosis will also improve long-term patency of venous grafts.
Internal Mammary Artery (IMA)
This is an excellent graft. When left internal mammary artery (LIMA) is anastomosed to LAD, which has more than 70 per cent block, patency at the end of two years is 99 per cent. It falls to 92 per cent at the end of ten years.The right internal mammary artery (RIMA) can be used in situ to bypa~s RCA, PDA or LAD. It can also be used as a free graft with proximal end anastomosed Lo aorta or left internal mammary artery (LIMA) as a T or Y graft. Long-term patency of free IMA is slightly lower than in silu IMA. In
another large series IMA patency was 90 per cent at ten years. After ten years there was no further fall when followed up to twenty years. Inlernal mammary artery is particularly resistant to athero sclerosis.
Radial Ahery (RA)
Patency of RA is less than that of Ih4.A but much superior to a venous graft.One of the studies showed 90 per cent patency at 13 months and 83 per cent at the end of seven years. LIMA patency was 91 per cent for the same period.
ICarriiovascular Surgery
GEA is seldom used now. Patency has been reported as 94 per cent at one year, 88 per cent at five years and 83 per cell1 at ten years.
Inferior Epigastric Artery IEA is also not used frequently these days. Rcported patency is 93 per ccnt at five years.
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