Prosthetic Heart Valves



Patients that have had a valve replacement will have a scar. Usually this will be a midline sternotomy scar straight down the middle of the sternum indicating a mitral or aortic valve replacement or CABG). Less commonly a right sided mini-thoracotomy incision can be used for minimally invasive mitral valve replacement surgery.

Bioprosthetic versus mechanical

Valves can be either replaced by a bioprosthetic or a metallic mechanical valve. “Porcine” bioprosthetic valves come from a pig.

Bioprosthetic valves have a limited lifespan of around 10 years.

Mechanical valves have a good lifespan (well over 20 years) but require lifelong anticoagulation with warfarin. The INR target range with mechanical valves is 2.5 – 3.5.

 

Types of Mechanic Heart Valves

Starr-Edwards valve

  • Ball in cage valve
  • Very successful but no longer being implanted
  • Highest risk of thrombus formation

Tilting disc valve

  • A single tilting disc

St Jude Valve

  • Two tilting metal discs
  • The two discs mean they are called bileaflet valve
  • Least risk of thrombus formation

Mechanical Heart Valves

Major Complications

  • Thrombus formation (blood stagnates and clots)
  • Infective endocarditis (infection in prosthesis)
  • Haemolysis causing anaemia (blood gets churned up in the valve)

Mechanical valves cause a click

  • A click replaces S1 for metallic mitral valve
  • A click replaces S2 for metallic aortic valve

Transcatheter Aortic Valve Implantation (TAVI)

This is a treatment for severe aortic stenosis, usually in patients that are high risk for an open valve replacement operation. It involves local or general anaesthetic, inserting a catheter in to the femoral artery, feeding a wire under xray guidance to the location of their aortic valve, then inflating a balloon to stretch the stenosed aortic valve and implanting a bioprosthetic valve in the location of the aortic valve.

Long term outcomes for TAVI are still not clear as it is a relatively new procedure. Therefore in younger, fitter patients open surgery is still the first line option.

Patient that have a TAVI do not typically require warfarin as the valve is bioprosthetic.

Infective Endocarditis

This occurs in around 2.5% of patients having a surgical valve replacement. The rate is slightly lower for TAVI at around 1.5%. Infective endocarditis in a prosthetic valve has quite a high mortality of around 15%. This is usually caused by one of three gram positive cocci organisms:

  1. Staphylococcus
  2. Streptococcus
  3. Enterococcus

 

Last updated November 2018
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