The office ruled that the cause of Breitbart's death was heart failure and hypertropic cardiomyopathy with focal coronary atherosclerosis, or hardening of the arteries.
Coroner's officials deemed the death "natural," and toxicology tests detected no illicit drugs in Breitbart's system. His blood-alcohol level was 0.04 percent.
Breitbart collapsed near his Los Angeles home March 1. He was 43.
Breitbart's father-in-law, actor Orson Bean, told the Los Angeles Times, "He was walking near the house somewhere. ... He was taken by paramedics to (the University of California-Los Angeles), and they couldn't revive him."
Breitbart spent his early professional life helping edit the Drudge Report and later helped launch the Huffington Post. In 2005 he started his own news aggregation site, Breitbart.com, which was designed to counter what he described as the "bully media cabal" that he said ignored stories at odds with prevailing liberal orthodoxy.
His goal, he often said, was to "destroy the institutional left."
His big splash came in 2009, when he posted an undercover video in which a pair of conservative activists posing as a prostitute and her boyfriend asked employees of the community group ACORN for help with a brothel that would house underage Salvadorans. ACORN was embarrassed when some of its workers seemed too helpful; Congress responded by defunding the organization.
Breitbart's mother-in-law, Alison Mills Bean, called Breitbart "one of the most genuine people I've met in my life. ... He always spoke the truth of his heart, and no matter what people agreed or disagreed with him, he never wavered.
His death produced polarizing responses online. Conservatives lamented the death of a visionary, and attacked the tweets from liberals who seemed unmoved by Breitbart's death.
Conservative commentator Michelle Malkin tweeted: "Even in death, andrewbreitbart exposes the rabid Left's intolerance."
Breitbart is survived by his wife, four children, a sister and his parents, Jerry and Arlene.
Breitbart lived with his family in Los Angeles' Westwood neighborhood. He was adopted by moderately conservative Jewish parents and attended two of L.A.'s most exclusive private schools -- Carlthorp and Brentwood.
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