Prosthetic valves Flashcards
Scar for valve replacement?
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 vs 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 mechanical 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
Complications of 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
TAVI?
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?
Causes?
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:
Staphylococcus
Streptococcus
Enterococcus
