6th May 2025

Mechanical valves

Mechanical valves are synthetic, typically a mix of carbon and metal, and come in a variety of designs and sizes. In the absence of complications, their lifespan can outlast that of the patient but they require lifelong anticoagulation with a vitamin K antagonist such as warfarin as DOACs have been shown to be less effective. The INR target range is dependent upon patient and anatomical factors, with valves in the mitral position typically requiring higher INR targets (typically 3-4) due to the lower flow velocity compared to the aortic position (typically 2.5-3.5). Complications of mechanical valves include bleeding, infection of prosthetic material, dehiscence of the valve and obstruction of the valve due to clot. 

Bleeding can occur in the setting of excess anticoagulation, while any prosthetic material in the body serves as a nidus for infection, thus all patients with prosthetic material are advised to be rigorous in their dental hygiene and to avoid tattoos and piercings where possible to avoid a potential route for the seeding of bacteria. Dehiscence (or displacement) of the valve can occur in the context of endocarditis, or less commonly due to ineffective suturing coming loose. Obstruction of the valve due to clot is an emergency as it will lead to haemodynamic collapse if it significantly impedes flow and will need treatment with either lysis via heparinisation or thrombolytics, or emergency valve surgery. This is typically demonstrated by evidence of higher velocity flow through the valve with evidence of reduced or arrested valve leaflet motion on imaging tests.