Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) Prevention What are blood clots? Normally, blood flows easily through your blood vessels. However, if a blood vessel becomes damaged or if the flow slows down or stops, a clot can develop and form a ‘plug’. This leaflet will answer some of your questions and concerns about deep vein thrombosis (DVT) and pulmonary embolism (PE). Preventing Deep Vein Thrombosis and Pulmonary Embolism View PDF