Warfarin is the drug of choice for long term management of patients with prosthetic valves. In fact, DOACs ( Direct oral antocoagulants) are contraindicated in such patients.

In patients with moderate COVID -19 infection, who do not have evidence of thrombosis, it is better to continue warfarin.

However, despite warfarin use, if the patient develops thrombosis, it is better to switch to enoxaparin for one month and then overlap with warfarin.

The need for low dose aspirin may also be considered in patients who are at a high risk of venous thrombosis despite using warfarin in COVID-19 infection.

This is my point of view and not evidence-based.

Why DOAC are contraindicated in pts e prosthetic valves?

Because the risk of valve thrombosis is high in patients on DOACs compared to warfarin.

Sir is the mechanism known why risk of thrombosis is greater with DAOCs or its just the statistics or studies based result ?