Pathology
- The principle blood supply to the heart is via three vessels
- Right coronary artery
- Left anterior descending artery
- Circumflex coronary artery
- Atherosclerosis occurs in the proximal portions of these vessels
- The main treatable risk factors for coronary artery disease are
- Hypercholesterolaemia
- Hypertension
- Diabetes
- Smoking
- Depending on number of vessels involved patient is described as having
- Single-vessel disease
- Double-vessel disease
- Triple-vessel disease
- Prognosis depends on
- Number of vessels involved
- Left ventricular function
Investigations
- Left ventricular function can be assessed by assessing ejection fraction on
- Echocardiography
- Angiography
- Multiple-gated acquisition (MUGA) scan
- Coronary angiography allows
- Confirmation of diagnosis
- Preoperative planning of site of graft
Indications for surgery
- Usually requires severe stenosis (>70%) with left main stem or triple vessel disease
- No improved survival seen in patients with single or double-vessel disease
- Improved survival seen in those with poor left ventricular function
- Similar survival seen in patients undergoing angioplasty for multi-vessel disease
Assessment of risk
- Patients at greatest risk have the most to gain from surgical intervention
- Mortality risk can be estimated using various scoring tools
- Risk is calculated by summating individual risk factors
Parsonnet score
- Age greater than 70 years +7%
- Age greater than 75 years +12%
- Age greater than 80 years +20%
- Female sex +1%
- Hypertension +3%
- Diabetes +3%
- Obesity +3%
- Good ejection fraction Nil
- Moderate ejection fraction +2%
- Poor ejection fraction +4%
Euroscore
- Age - for each 5 years over 60 years +1%
- Female sex +1%
- Chronic respiratory disease +1%
- Extracardiac arteriopathy +2%
- Neurological dysfunction +2%
- Creatinine greater than 200 µmol/l +2%
- Previous cardiac surgery +3%
- Unstable angina +2%
- Recent myocardial infarction +2%
- Good ejection fraction Nil
- Moderate ejection fraction +1%
- Poor ejection fraction +3%
Choice of conduit
- Conduits can be either venous or arterial
- Long saphenous vein is easy to harvest by a second surgeon
- Allows multiple grafts to be fashioned
- Has patency rate of 60% at 10 years
- Left internal mammary artery as been used to graft the left anterior descending
- Patency rate of 90% at 10 years has been reported
Surgery
- Chest is entered via a median sternotomy
- Left internal mammary artery is dissected
- Long saphenous vein can be harvested and prepared by second surgeon
- Heart is cannulated and patient is placed on bypass
- Aorta is cross clamped
- Injury to heart reduced by cardioplegic solutions
- Cardioplegia can be either warm (37 degrees) or cold (4 degrees)
- Recent advances include
- Off-pump coronary artery surgery
- Minimally invasive direct coronary artery surgery
- Both can avoid either bypass or median sternotomy
Picture provided by Philip Edelmann, University of Innsbruck, Austria
Complications
- Bleeding
- Atrial fibrillation
- Wound infection
- Poor cardiac function
- Stroke
Bibliography
Lancey R A. Off-pump coronary artery bypass surgery. Curr Probl Surg 2003; 40:
693-802.
Lodolfo K P. Minimally invasive cardiac surgery. Ann Surg 2003; 238 (Suppl
6); S110-11.
Westaby S. Coronary revascularisation in ischemic cardiomyopathy. Surg Clin North Am
2004; 84; 179-199.
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