Ritter was rushed from the set of the ABC series "8 Simple Rules for Dating My Teenage Daughter" to Providence St. Joseph Medical Center in Burbank, California, after suffering from aortic dissection, an unrecognized and undetected flaw in his heart, according to a statement from his publicist Lisa Kasteler.

"Surgeons at the hospital tried to save the Emmy Award-winning actor but, sadly, were unable to do so," the statement said.

WebMD.com describes an aortic dissection as "an abnormal separation of tissues within the walls of the aorta" caused by high blood pressure, family history of the condition, disease of connective tissue, or severe trauma to the chest.

"Aortic dissection results in a weakened blood vessel wall that may also rupture," the Web site says.

Ritter, who would have turned 55 next week, is best known for his role as Jack Tripper on the long-running television sitcom, "Three's Company," which brought him an Emmy.

Actress Suzanne Somers remembered her former "Three's Company" co-star as a man of "great joy" and said he was one of the finest physical comedy actors she had ever known

"The chemistry that people see on that show is the chemistry we had," Somers told CNN's Larry King in a phone interview. "I loved John Ritter. He was like playing ping-pong with a great player, he'd just bang the ball and you better be fast to get it. And he also had a great joy."

Ritter was the youngest son of Western film star and country music legend Tex Ritter, according to his biography on ABC's Web site.