Doctors at St. Luke's Episcopal Hospital have stressed that Ryan, 53, did not suffer a heart attack when he checked in Monday.
Ryan, who underwent double-coronary bypass surgery April 23, was found to suffer from angina, described by Dr. James T. Willerson as brief spasms caused by not enough oxygen to the heart muscle.
"No surgery is needed at this time," Willerson said. "It's just a matter of finding the right level of medication to treat his symptoms."
Ryan threw a major-league record 5,714 strikeouts and seven no-hitters during his 27-year career with the New York Mets, California Angels, Houston Astros and Texas Rangers.
The 324-game-winner entered the Hall of Fame last year. He and his wife, Ruth, live in their hometown of Alvin, just south of Houston.
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