Cardiac Surgery

Question 1

Indications for CABG

Answer 1

• >50% stenosis of the left main stem (‘critical left main stem disease’)
• 2-3 main coronary arteries diseased (‘triple vessel disease’)
• Poor ventricular function associated with multi-vessel disease

Question 2

Cardiopulmonary bypass

Answer 2

• Any operation that involves stopping the heart
• Herparinise patient (avoid blood clotting in CPB circuit)
• Cannulate and connect to bypass circuit (ascending aorta and RA/SVC and IVC)
• Venous return siphoned into bypass circuit where it is oxygenated, filtered, cooled/warmed and returned to patient via aortic cannula
• Once finisihed, heparin reversed with protamine

Question 3

Cardioplegia

Answer 3

• Bypass doesn’t stop heart - just bypasses beating heart
• Cardioplegia is a K+ rich solution based on blood/crystalloid
• Delivered into coronary arteries
• Arrests heart and prevents myocardial ischaemia
• Static operating field for surgeon

Question 4

CABG

Answer 4

• Select grafts:
  
  • Venous (long saphenous)
  • Arterial (left internal mammary/internal thoracic)
• Harvested prior to bypass
• Sternotomy
• LIMA not detached and attached to LAD
• Venous grafts to aorta and distal to occlusion

Question 5

Post-operative complications

Answer 5

• Bleeding
• Arrhythmias (commonly sinus tachycardia/AF)
• Poor cardiac output (may require inotropes)
• Stroke
• Wound infections
• Mortality (2-3%)

Question 6

Indications for aortic valve replacement

Answer 6

• Severe AS with symptoms/reduced exercise tolerance
• Severe AS with EF <50%
• Moderate-severe will be considered for replacement if undergoing other cardiac surgery
• Severe AR/progressive AR and undergoing other cardiac surgery
• Aortic valve always replaced in adults and never repaired

Question 7

Aortic valve replacement

Answer 7

• Procedure of choice for those deemed fit for open heart surgery
• Mechanical valve
• Life expectancy vs lifelong anticoagulation
• Concurrent bypass grafting possible

Question 8

Transcatheter aortic valve implantation (TAVI)

Answer 8

• For those meeting criteria for AVR but high surgical risk
• No open heart surgery (small left mini thoracotomy) and no bypass

Question 9

Mechanical vs tissue valves

Question 10

Indications for mitral valve repair/replacement

Answer 10

• Severity of MR
  
  • Mild/moderate - none
  • Severe - if symptomatic/change in LV
• Symptoms
  
  • Asymptomatic - only if severe/change in LV function
  • Symptomatic - if severe disease
• Papillary muscle rupture (i.e. post-MI)

Question 11

Repair vs replacement

Answer 11

• Annuloplasty (ring inserted with aim of restoring physiological form of now distorted mitral valve +/- refashioning or insertion of new cords)
• Superior to replacement where possible (aim to conserve mitral valve apparatus and lessen chances of systolic dysfunction)