WASHINGTON — Mikhail Lesin, a former aide to Russian President Vladimir Putin who helped found the English-language news service Russia Today, was found dead in an upscale Washington hotel room, police and Russian authorities said. He was 57. The Russian Embassy in Washington on Friday confirmed the death of Lesin, whose body was discovered Thursday. Russia Today reported on its website that Lesin died of a heart attack, and the state news agency RIA-Novosti cited a family member giving the same cause of death. District of Columbia police said officers were called to Lesin’s room at the Doyle Dupont Circle Hotel on Thursday morning to check on his welfare.