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Graft patency of saphenous vein and internal thoracic artery
Asia Pacific Heart J 1997;6(3)
Live Teleconference on Complete Arterial Grafting SUPPLEMENT
but are less well appreciated when considering vasoreactivity of arterial conduits.
Myointimal
the
Hyperplasia
Myointimal hyperplasia is a major factor in restenosis after PTCA. It seems to be involved in the narrowing of the anastomosis in 2-5% of patients after CABG. Cmyb inhibitor, locally delivered, can experimentally prevent mobilisation of muscle cells and restenosis (Fig 2).
Cardiovascular Risk Factors Bypass graft function and patency are known to be negatively influenced by cardiovascular risk factors such as atherosclerosis, diabetes, hypertension and smoking. In normal conditions, the reactivity of the media to vasoconstrictor agents is regulated by the endothelium through the basal release of nitric oxide. Normally, the endothelium protects the vascular smooth muscle cells in arterial grafts from vasoconstrictor agents, but an increase in the production of endothelin (for example, by thrombin or TGF-b released at sites of activated coagulation and platelets) may increase vascular tone and endanger graft blood flow.
Fig. 2. Cell membrane swelling is a major factor in the “noreflow phenomenon”.
Conclusion Vasoreactivity of coronary grafts is effective not only during the perioperative period but several years after surgery. Perioperative and late precautions are necessary to prevent vasospasm including surgical technique, calcium entry blockers and antiplatelet agents. In the future, myointimal hyperplasia could be prevented by perioperative antisense therapy (Fig 3). In all cases, the risk factors of atherosclerosis have to be carefully controlled.
Fig. 3. Mean neointimal thickness after migration of smooth muscle cells evaluated in micrometers; significant differences between the antisenseand the control groups (~~0.03) and the antisenseand the sensegroups (~~0.05)
Graft Patency Of Saphenous Vein And Internal Thoracic Artery John A. Fuller, FRACS, Brian Buxton, FRACS, JamesTatoulis, FRACS Epworth Hospital and the University of Melbourne Group, Melbourne, Victoria, Australia In contrast, internal thoracic artery patency was considerably better. The Cox model identified 2 adverse factors: free internal thoracic artery graft (RR, 2.7) and internal thoracic artery graft to a coronary artery with a stenosisless than 60% (RR, 2.1). Internal thoracic artery grafts to the LAD conveyed a superior patency rate (RR, 0.5) while those to the RCA a poorer patency (RR, 3.5). The 5-year patency of internal thoracic artery graft was 0.97; 7-year, 0.96, and lo-year, 0.90. Failure of the right internal thoracic artery graft to the right coronery artery has been circumvented by using a free graft to the posterior descending branch.
Introduction Reangiography for recurrence of symptoms after coronary artery surgery allowed 3,100 grafts to be studied in 1,003 patients who underwent operation between 198 1 and 1990. The grafts included 2,280 vein grafts and 820 arterial grafts (of which 546 were left internal thoracic arteries, 244 right internal thoracic arteries, 27 radial arteries and 3 inferior epigastric arteries). Graft failure was defined as a graft stenosis of 80% or more.
Analysis Analysis using the Cox model of proportional hazards identified 5 adverse factors for saphenous vein grafts: cholesterol greater than 6.4 (rate risk ratio, 1.3), thick vein (RR 1.7), sequential vein grafts (RR, 1.6), male gender (RR, 1.3) and the ratio of vein-to-artery diameter (if this ratio exceeds 1.4, an added risk of graft occlusion occurs with a risk ratio of 1.3). Saphenous vein grafts to the LAD convey a slightly improved risk (RR, 0.8). At best, the saphenous vein graft carried a poor long-term patency rate with a 5-year patency of 0.95; 7 years, 0.84, and 10 years, 0.50.
Conclusion The superior patency rate of pedicled arterial grafts recommends their use in coronary artery surgery wherever possible. However, if a saphenous vein graft is unavoidable, it is preferable to ensure that its size is commensurate with the coronary artery grafted, and that the patient’s cholesterol level is carefully controlled.
209
Live Teleconference on Complete Arterial Grafting SUPPLEMENT
but are less well appreciated when considering vasoreactivity of arterial conduits.
Myointimal
the
Hyperplasia
Myointimal hyperplasia is a major factor in restenosis after PTCA. It seems to be involved in the narrowing of the anastomosis in 2-5% of patients after CABG. Cmyb inhibitor, locally delivered, can experimentally prevent mobilisation of muscle cells and restenosis (Fig 2).
Cardiovascular Risk Factors Bypass graft function and patency are known to be negatively influenced by cardiovascular risk factors such as atherosclerosis, diabetes, hypertension and smoking. In normal conditions, the reactivity of the media to vasoconstrictor agents is regulated by the endothelium through the basal release of nitric oxide. Normally, the endothelium protects the vascular smooth muscle cells in arterial grafts from vasoconstrictor agents, but an increase in the production of endothelin (for example, by thrombin or TGF-b released at sites of activated coagulation and platelets) may increase vascular tone and endanger graft blood flow.
Fig. 2. Cell membrane swelling is a major factor in the “noreflow phenomenon”.
Conclusion Vasoreactivity of coronary grafts is effective not only during the perioperative period but several years after surgery. Perioperative and late precautions are necessary to prevent vasospasm including surgical technique, calcium entry blockers and antiplatelet agents. In the future, myointimal hyperplasia could be prevented by perioperative antisense therapy (Fig 3). In all cases, the risk factors of atherosclerosis have to be carefully controlled.
Fig. 3. Mean neointimal thickness after migration of smooth muscle cells evaluated in micrometers; significant differences between the antisenseand the control groups (~~0.03) and the antisenseand the sensegroups (~~0.05)
Graft Patency Of Saphenous Vein And Internal Thoracic Artery John A. Fuller, FRACS, Brian Buxton, FRACS, JamesTatoulis, FRACS Epworth Hospital and the University of Melbourne Group, Melbourne, Victoria, Australia In contrast, internal thoracic artery patency was considerably better. The Cox model identified 2 adverse factors: free internal thoracic artery graft (RR, 2.7) and internal thoracic artery graft to a coronary artery with a stenosisless than 60% (RR, 2.1). Internal thoracic artery grafts to the LAD conveyed a superior patency rate (RR, 0.5) while those to the RCA a poorer patency (RR, 3.5). The 5-year patency of internal thoracic artery graft was 0.97; 7-year, 0.96, and lo-year, 0.90. Failure of the right internal thoracic artery graft to the right coronery artery has been circumvented by using a free graft to the posterior descending branch.
Introduction Reangiography for recurrence of symptoms after coronary artery surgery allowed 3,100 grafts to be studied in 1,003 patients who underwent operation between 198 1 and 1990. The grafts included 2,280 vein grafts and 820 arterial grafts (of which 546 were left internal thoracic arteries, 244 right internal thoracic arteries, 27 radial arteries and 3 inferior epigastric arteries). Graft failure was defined as a graft stenosis of 80% or more.
Analysis Analysis using the Cox model of proportional hazards identified 5 adverse factors for saphenous vein grafts: cholesterol greater than 6.4 (rate risk ratio, 1.3), thick vein (RR 1.7), sequential vein grafts (RR, 1.6), male gender (RR, 1.3) and the ratio of vein-to-artery diameter (if this ratio exceeds 1.4, an added risk of graft occlusion occurs with a risk ratio of 1.3). Saphenous vein grafts to the LAD convey a slightly improved risk (RR, 0.8). At best, the saphenous vein graft carried a poor long-term patency rate with a 5-year patency of 0.95; 7 years, 0.84, and 10 years, 0.50.
Conclusion The superior patency rate of pedicled arterial grafts recommends their use in coronary artery surgery wherever possible. However, if a saphenous vein graft is unavoidable, it is preferable to ensure that its size is commensurate with the coronary artery grafted, and that the patient’s cholesterol level is carefully controlled.
209