Answer by taking a quote from the following article:

Jeanette Anna MacDonald (June 18, 1903 - January 14, 1965) was an American singer and actress best remembered for her musical films of the 1930s with Maurice Chevalier (The Love Parade, Love Me Tonight, The Merry Widow and One Hour With You) and Nelson Eddy (Naughty Marietta, Rose-Marie, and Maytime). During the 1930s and 1940s she starred in 29 feature films, four nominated for Best Picture Oscars (

In the mid-1950s, MacDonald toured in summer stock productions of Bitter Sweet and The King and I. She opened in Bitter Sweet at the Iroquois Amphitheater, Louisville, Kentucky, on July 19, 1954. Her production of The King and I opened August 20, 1956, at the Starlight Theatre. While performing there, she collapsed. Officially, it was announced as heat prostration, but in fact it was a heart seizure. She began limiting her appearances and a reprisal of Bitter Sweet in 1959 was her last professional appearance.  MacDonald and her husband, Gene Raymond, toured in Ferenc Molnar's The Guardsman. The production opened at the Erlanger Theater, Buffalo, New York, on January 25, 1951, and played in 23 northeastern and midwestern cities until June 2, 1951. Despite less than enthusiastic comments from critics, the show played to full houses for virtually every performance. The leading role of "The Actress" was changed to "The Singer" to allow MacDonald to add some songs. While this pleased her fans, the show still closed before reaching Broadway.  In the 1950s, talks with respect to a Broadway return occurred. In the 1960s, MacDonald was approached about starring on Broadway in a musical version of Sunset Boulevard. Harold Prince recounts in his autobiography, visiting MacDonald at her home in Bel Air to discuss the proposed project. Composer Hugh Martin also wrote a song for the musical entitled, "Wasn't It Romantic?".  MacDonald also made a few nightclub appearances. She sang and danced at The Sands and The Sahara in Las Vegas in 1953, The Coconut Grove in Los Angeles in 1954, and again at The Sahara in 1957, but she never felt entirely comfortable in the smoky atmosphere.

Did was survive the collapse?
Officially, it was announced as heat prostration, but in fact it was a heart seizure.