I am a Principal Investigator in the Asymptomatic Carotid Surgery Trial (ACST-2), one of the world's largest clinical surgery trials, involving thousands of patients from 30 countries. Our group reported that prophylactic surgery removing tight carotid artery narrowing (carotid endarterectomy) prevents future fatal and disabling strokes for at least 10 years. This finding has changed worldwide surgical and stroke practice (Lancet 2004, 2010).