Prosthetic Valves

There are two main types of prosthetic valves:

• Mechanical, non tissue valves
• Porcine, bovine or human tissue valves

Prosthetic valves can last decades but patients should be attending regular follow up to detect any deterioration which could then progress rapidly.
Acute problems with prosthetic valves are categorised as follows:

Valve thrombus and embolisation

Mechanical valves require life long anticoagulation; valve thrombosis is often associated with inadequate anticoagulation therapy. It is more common with mitral than aortic valves. Thrombotic obstruction of a tissue valve is rare.

A patient may present in cardiogenic shock, with systemic embolisation (cerebral infarction) or with sudden death. The diagnosis should be suspected if the patient is known to have a mechanical valve and the distinctive crisp click sound is reduced on auscultation. Echocardiography is needed to confirm the diagnosis. In a cerebral vascular event a CT scan should be performed to exclude a bleed.

Treatment consists of heparin anticoagulation or as necessary thrombolysis, thrombectomy or valve replacement.

Endocarditis

This is most common in the first 2 months post valve surgery and usually is caused by wound infection or an intravenous line. Late infections are caused by the same organisms which infect native valves. All patients with prosthetic valves should have antibiotic prophylaxis.

Prosthetic valves and acute haemorrhage

In acute haemorrhage the risk of causing valve thrombosis is outweighed by the risk of on going bleeding. Warfarin should be reversed (in consultation with haematology services). When stable, the patient should receive heparin and warfarin restarted.