Prosthetic Valves Flashcards
If the metallic click is heard in the first heart sound, which valve has been replaced
Mitral
If the metallic click is heard in the second heart sound, which valve has been replaced
Aortic
What else might you hear on auscultation of a patient with a prosthetic valve
Systolic flow murmur
What might be heard with bioprosthetic valves
Normal heart sounds
What should the INR be kept at in patients with mechanical heart valves
3-4
How long do mechanical heart valves last
15 years
What type of biological heart valves are there
Xenograft - porcine valve, no warfarin required, lasts 10 years
Homograft - cadaveric valve graft, more durable than xenograft
What is the operative mortality in valve replacement surgery
3-5%
In which patients would a bioprosthetic valve be more suitable
Any patient in whom anticoagulants are contraindicated
Patients over 70
In which patients would a mechanical valve be recommended
Patients less than 60 without contraindications to anticoagulation therapy
What medication should be given to all patients with a prosthetic heart valve
75-100mg aspirin
What other medication should be given to patients with a mechanical heart valve
Warfarin
When should prophylactic antibiotics be given against infective endocarditis
To patients with prosthetic valves before certain types of dental surgery American Heart Association Guidelines
NICE guidelines say no prophylactic antibiotics needed
What organism most commonly causes endocarditis following dental surgery
S. viridans
What is the most common causative organism of IE within 2 months of operation for a prosthetic valve
Staphylococcus epidermidis
What antibiotics would be used as endocarditis prophylaxis prior to dental surgery
Single dose amoxicillin
What antibiotic would you give as endocarditis prophylaxis if a patient was allergic to penicillin
Cephalexin
What is the mechanism of action of warfarin
Vitamin K antagonist
How is warfarin metabolised
Cytochrome P450
What drug interactions with p450 enzymes affect warfarin
Cytochrome p450 inducers reduce warfarin efficacy Cytochrome p450 inhibitors increase warfarin levels
What are some examples of cytochrome p450 inducers
NSAIDs and aspirin
Anti-convulsants
Anti-TB e.g. Rifampicin
What are some examples of cytochrome p450 inhibitors
Antibiotics eg. ciprofloxacin, clarithromycin
Antifungals e.g. fluconazole
What are the complications of a valve prosthesis?
Complications from surgery- general risks of haemorrhage, infection and anaesthetic risks (mortality of 5%)
Complications from valve itself: Haemolysis, infective endocarditis (may require 2nd replacement), valve dysfunction (leakage, dehiscence), thromboembolism
Complications from anticoagulation: Bleeding
What are the complications of prosthetic valves?
Valvular:
- Valve dysfunction e.g. Leakage, dehiscence, obstruction from thrombosis, fibrosis, clogging
Infectious:
- Endocarditis
Haematological:
- Thromboembolism
- Haemolysis
- Complications of anti coagulation e.g. Bleeding
