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AORTIC VALVE SURGERY (AVR)

  

AVR stands for Aortic Valve Repair or Aortic Valve Replacement.

 

Surgery on the aortic valve is more often replacement, however, some centres do repair procedures.

 

 

Indications

  • Aortic valve stenosis – see details. Surgery for aortic stenosis is usually replacement
  • Aortic valve incompetence – see details
  • Undergoing another cardiac procedure such as a CABG and there is coexistent aortic valve disease

 

 

Types of Replacement

  • Metallic – largely replaced by prosthetic, bioprosthetic or tissue valves.
  • Prosthetic – widely used. Non-metallic. Bi-leaflet is the valve of choice today.
  • Bioprosthetic – combination of tissue and prosthetic material (PTFE)
  • Tissue – from animal tissue (Xenograft) or from human tissue (heterograft/allograft or autograft)

 

 

  Pre-Operative

  • Proper Dental Care - may need prophylactic antibiotics. A visit to the dentist for check-up, and more if needed, is very common, recommended, and often insisted on by surgeons prior to the operation.
  • Bloods - haemoglobin/anaemia; infection/inflammatory markers; coagulation/clotting; renal function; group and save/crossmatch.
  • Urine dipstick - urine is a good source of bugs that can infect the valve, causing endocarditis - DISASTER!
  • Echocardiogram - to quantify the severity of the disease. Are there any other coexistent abnormalities?
  • Cardiac Catheterisation -to assess coronary arteries for possible revascularisation.

 

 

 Alternatives to Surgery

  • Pharmacotherapy - no effective medical treatment. May improve symptoms (Diuretics, Digitalis).
  • Balloon Aortic Valvuloplasty (BAV) - immediate results and durability are not at all impressive. Now rarely used
  • Percutaneous Aortic Valve Replacement – used mostly for patients unable to tolerate surgery.

 

 

Challenges of Aortic Valve Surgery

  • Proximity to other structures - the aortic valve is in very close proximity to some very important structures. These include the ostia of the right and left coronary arteries, the atrioventricular conduction bundle, and the mitral valve. This close proximity, and in some cases continuity, adds to the challenge, and potential complications, of aortic valve surgery.
  • The very sick patient - due to cormobidities some patients, who desparately need a new valve, are too high risk for surgical aortic valve replacement. This is where percutaneous aortic valve replacement has its principal indication.
  • Anticoagulation – The dilemma lies particularly with the bioprosthetic valves with regard to the choice of and the length of time of anticoagulation. This may vary from hospital to hospital or even from consultant to consultant. Mechanical and purely prosthetic valves are generally put on lifelong warfarin. The pure tissue valves are generally not put on warfarin. However, it is now widely appreciated that formal anticoagulation (warfarin) is appropriate in at least the first three months following insertion of a valve with any form of prosthetic in it, hence bioprosthetic valves will normally be anticogulated for at least the first three months following surgery. This (three months) is the period of time it takes for endothelialisation of the prosthetic component of the valve. Before endothelialisation there is the highest risk of thromboembolism.

 

 

References

  • Oxford Handbook of Cardiothoracic Surgery. Chikwe, Beddow, Glenville, 2006
  • Cardiac Surgery in the Adult. Lawrence Cohn, 2008
  • ACC/AHA 2006 Guidelines for the Management of Patients with Valvular Heart Disease. J. Am Coll. Cardiol. 2006; 48;e1-e148