Coronary%20artery%20bypass%20grafting

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Coronary artery bypass grafting

• CABG - OPCAB

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Coronary artery disease

• Definition
• Narrowing of the coronary arteries
• Caused by thickening and loss of elasticity of
  the arterial walls
• Limiting blood flow to the myocardium
• Flow reserve (effort)
• At rest
• Occlusion

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Coronary artery disease

• Morphology and processes
• Focal intimal accumulation of lipids, blood
  elements, fibrous tissue, calcium etc. with
  associated changes in the media
• ? Plaque
• ? Stenosis
• Regression of plaque and collateral formation
• Plaque rupture and thrombosis
• Usually affects multiple coronaries
  simultaneously, proximally and at bifurcations

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Myocardial infarction

• Imbalance between oxygen supply and demand
• Myocardial necrosis starts after 20 minutes
• Border zone
• Reperfusion within 3-4 hours can limit the extent
  of myocardial necrosis
• Scarring. LV systolic and diastolic dysfunction.
  Chronic heart failure.

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Diagnosis

• Symptoms Angina pectoris, acute myocardial
  infarction, chronic heart failure, sudden death,
  incidental finding on ECG
• Noninvasive tests to identify and quantify CAD
  and sequelae ECG, CXR, Labs, Exercise testing,
  Nuclear scans, Echocardiography, CT (Ca)

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Diagnosis

• Associated conditions
• Atherosclerosis carotids, PAD
• Definitive diagnosis extent, distribution and
  severity of anatomic coronary artery disease
• Coronary angiography
• New modalities CT (MRI)

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Coronary angiography

• Grading of stenoses
• Moderate 50 diameter 75 cross-sectional area
  loss
• Severe 67 diameter 90 cross-sectional area
  loss
• Distribution
• Single system / two system / three system
• Left main

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Coronary anatomy
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Indications for surgery

• Comparative benefit of surgery relative to no
  treatment / medical treatment / PCI
• Enormous variability in CAD, impacting on risk
  calculation ? patient-specific predictions
• General indications
• Left main or left main equivalent
• 3 system disease
• 2 system disease with severe prox. LAD and LVEF lt
  50 or ischemia on non-invasive testing
• 1 or 2 system disease with large area of viable
  myocardium and high-risk criteria

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Bypass grafting

• Full sternotomy and CPB (HLM)
• CABG
• Full sternotomy, no CPB
• OPCAB
• Small sternotomy, parasternal access,
  thoracotomy, with or without CPB
• e.g. MIDCAB

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Bypass grafting

• CABG Golden standard and still most widely used
  (STS database 80)
• Objective complete revascularisation by
  bypassing all severe stenoses in all affected
  coronary branches with 1-1.5 mm diameter
• Most widely used conduits LIMA, RIMA, SVG,
  radial artery, gastro-epiploic artery

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ConduitsLIMA / RIMA
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ConduitsSVG
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ConduitsRadial
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ConduitsGastro-epiploic
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Conduit configurations
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Endarter-ectomy
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CABG

• Median sternotomy
• Conduit harvesting
• Heparin, cannulation and CPB with mild to
  moderate hypothermia
• Cross-clamping of the aorta and cardioplegia
• Distal anastomoses. Rewarming started.
• Cross-clamp removed. Proximal anast. using a
  partially occluding clamp. Clamp removed.
  De-airing.
• CPB discontinued, cannulae removed, protamine.
• Pacing wires, drainage tubes, hemostasis and
  closure.

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CABG
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OPCAB

• Attempt to maintain normothermia
• Median sternotomy
• Conduit harvesting
• Heparin. Pacing wires.
• Maneuvers to maintain hemodynamic stability
  (Trendelenburg, table, R pleura,.)
• Pericardial sling
• Luxation. Stabilisation. Distal anastomoses with
  or without shunting.
• Proximal anastomoses. Protamine.
• Chest drains. Hemostasis. Closure.

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Not discussed

• IABP and other support devices
• Emergency surgery
• Redo surgery
• Other modalities of bypass grafting MIDCAB,
  robotic surgery,
• Adjunctive surgical treatment TMLR, growth
  factors, cell transplantation
• Combined surgery

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Results

• Early mortality can be predicted, using risk
  stratification models (Euroscore, STS)
• Time-Related Survival, generally
• 1 month 98
• 1 year 97
• 5 year 92
• 10 year 81
• 15 year 66
• NB 25 of early and late deaths are not
  related to CAD or CABG

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Time-Related Survival
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Results

• Freedom from angina 60 at 10 years
• Freedom from AMI 86 at 10 years
• Freedom from sudden death 97 at 10 years
• 80 of patients are working 1 year postop.
• Graft patency
• LIMA (to LAD) 90 at 10 and 20 years.
• Radial artery 80 at 7 years
• Gastro-epiploic artery 60 at 10 years
• SVG 50-60 at 10 years, 80 to LAD