Prosthetic heart valves

Question 1

Scars from prosthetic heart valves tend to be where?

Answer 1

Usually this will be amidline sternotomy scarstraight down the middle of the sternum indicating amitraloraorticvalve replacementorCABG).

Less commonly aright sided mini-thoracotomyincision can be used for minimally invasivemitral valvereplacement surgery.

Question 2

Bioprosthetic versus mechanical valves?

Answer 2

Valves can be either replaced by abioprostheticor a metallicmechanicalvalve. “Porcine” bioprosthetic valves come from a pig.

Bioprosthetic valves have a limited lifespan of around 10 years.

Mechanical valveshave a good lifespan (well over 20 years) but requirelifelonganticoagulation withwarfarin. TheINR target rangewith mechanical valves is2.5 – 3.5.

Question 3

Types of mechanic heart valves?

Answer 3

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 calledbileaflet valve
- Least risk of thrombus formation

Question 4

Major complications of mechanical heart valves?

Answer 4

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

Question 5

Mechanical valves cause a click:

Answer 5

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

Question 6

Transcatheter Aortic Valve Implantation (TAVI)

Answer 6

This is a treatment forsevere 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 thefemoral artery, feeding a wire underxray guidance to the location of their aortic valve, then inflating a balloon to stretch the stenosed aortic valve and implanting abioprosthetic valvein 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.

Question 7

Infective endocarditis & valve replacement?

Answer 7

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 threegram positive cocci organisms:

1. Staphylococcus
2. Streptococcus
3. Enterococcus