Doctors at a Rome hospital battled for 40 minutes to try to save the life of James Gandolfini, best known for his Emmy-winning role as a mob boss in the TV series "The Sopranos," before pronouncing him dead, the emergency room chief said on Thursday.

Gandolfini, 51, whose performance as Tony Soprano made him a household name and help usher in a new era of American television drama, was vacationing in Rome and had been scheduled to attend the closing of the Taormina Film Festival in Sicily on Saturday.

He was taken from his Rome hotel to the city's Umberto hospital late on Wednesday, according to a hospital spokesperson.

The actor's 13-year-old son, Michael, had found him collapsed in the bathroom of his Rome hotel room, Gandolfini's manager, Mark Armstrong, said in an email.

"The resuscitation maneuvers, including heart massage, etc., continued for 40 minutes and then, seeing no electric activity from the heart, this was interrupted and we declared James dead," Claudio Modini, the emergency room chief, told Reuters.

"The patient was considered dead on arrival, and for that reason an autopsy has been requested to be carried out by a pathologist, as is normal procedure in our country."

The autopsy has been scheduled for Friday morning.

Since "The Sopranos" ended its six-season run in June 2007, Gandolfini appeared in a number of big-screen roles, including the crime drama "Killing Them Softly" and "Zero Dark Thirty," a film about the hunt for Osama bin Laden.

Academy Award winner Kathryn Bigelow, who directed Gandolfini in the film, said she was devastated by the news of his death.

"James was such an enormous talent, and an even greater spirit. I will be forever grateful for the privilege of working with him, and shall cherish his memories always," she said in a statement.

At the time of his death, Gandolfini had been working on an upcoming HBO series, "Criminal Justice," and had two motion pictures due out next year

Actress Edie Falco, who played Tony Soprano's long-suffering wife, Carmela, in "The Sopranos," said her co-star was a man of "tremendous depth and sensitivity."

"I consider myself very lucky to have spent 10 years as his close colleague," she said.

Apart from Michael, his son with his first wife whom he divorced in 2002, Gandolfini is survived by wife, Deborah Lin, a model he married in 2008, and baby daughter Liliana, born last year.

Role took its toll

Gandolfini gained sudden fame after years toiling as a character actor and garnered widespread respect from fellow actors.

Brad Pitt, who appeared in three films with Gandolfini, called him "a ferocious actor" and said he was "gutted by this loss."

In the HBO series, the burly, physically imposing Gandolfini created a gangster different from any previously seen in American television or film.

He was capable of killing enemies with his own hands but was prone to panic attacks. He loved his wife and was a doting father, but he carried on a string of affairs.

He regularly saw a therapist, portrayed by Lorraine Bracco, to work out his anxiety problems and issues with his mother. The vulnerable side of Tony Soprano made his detestable character deeply likable.

By the start of the show's final season, Gandolfini suggested he was ready to move on to more gentle roles.

"I'm too tired to be a tough guy or any of that stuff anymore," he said. "We pretty much used all that up in this show."

"The Sopranos" cast was also known for its hard-partying ways off set, and Falco, who has worked to stay sober since the early 1990s, confessed in a 2007 interview with New York magazine that hanging out with the cast was "too dangerous."

In 2002, a representative for Gandolfini confirmed to the New York Daily News and other media organizations that Gandolfini had struggled in the past with substance abuse problems, a revelation that first surfaced in connection with a contentious divorce battle with his first wife, Marcy Wudarski.

'Humble, Loyal, Complicated'

Gandolfini began his career as a stage actor in New York and earned a Tony nomination for his role in the original 2009 Broadway cast of the dark comedy "God of Carnage."

The actor, who was raised in a working-class family, shared Tony Soprano's Italian-American heritage and New Jersey roots. He was known for his reserved demeanor off-camera and generally shied away from publicity.

"The Sopranos" earned Gandolfini three Emmy Awards as best lead actor in a drama series and was considered by many critics the finest drama to have aired on US television.

The series was a major factor in establishing HBO, a pay-cable network once focused on presentations of feature films, as a powerhouse of original dramatic television and in shifting the kind of sophisticated storytelling once reserved for the big screen to TV.

His role paved the way for other popular prime-time shows built around profoundly flawed characters and anti-heroes, from "Dexter" and "Breaking Bad" to "Mad Men" and "Nurse Jackie."

Script writer Steve Zaillian, who worked with the actor before and after "The Sopranos," said he had always been the same man.

"A real man, like they don't make anymore. Honest, humble, loyal, complicated, as grateful for his success as he was unaffected by it, as respectful as he was respected, as generous as he was gifted. He was big, but even bigger-hearted," he said.

Gandolfini is due to appear on the big screen next year, playing the love interest of comic actress Julia Louis-Dreyfus in the film "Enough Said." He also has a role in the upcoming New York crime drama, "Animal Rescue."

Both are set for US release by News Corp-owned studio Fox Searchlight.