Thrombosis is the formation of a blood clot in a blood vessel. Once formed, a clot can slow or block normal blood flow, and even break loose and travel to an organ. Thrombosis is the often preventable underlying pathology of heart attack, thromboembolic stroke, and venous thromboembolism (VTE), the top three cardiovascular killers. VTEs are serious, life-threatening conditions that require immediate medical attention. 1 in 4 people worldwide are dying from conditions caused by thrombosis.