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Coronary artery surgery

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

Long saphenous vein harvest

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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