Leslie Charleson, who for nearly five decades played a dedicated cardiologist and passionate matriarch of a wealthy family on the ABC soap opera “General Hospital,” becoming one of the most enduring cast members in daytime television, died on Sunday at a hospital in Los Angeles. She was 79.

Frank Valentini, the executive producer of “General Hospital” confirmed her death in a statement on social media on Sunday. Ms. Charleson died of complications from a long illness, according to Marianne Price, a spokeswoman for the show.

Mr. Valentini said that just as her character, Dr. Monica Quartermaine, was the heart of the Quartermaine family on the show, the actress was the “matriarch of the entire cast and crew.”

Ms. Charleson joined the cast in 1977 as a cardiologist at the hospital where much of the show is set. Since 1963, the series has followed the lives of hospital staff members and residents in the fictional town of Port Charles, N.Y.

Ms. Charleson, who appeared in more than 2,000 episodes, began endearing fans after her character married into the wealthy and volatile Quartermaine family as the wife of Dr. Alan Quartermaine, who was played by Stuart Damon.

For decades, story lines revolved around their turbulent marriage, which involved fights, affairs, breakups and even murder attempts.

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