March 6, 2009 -- Comedian and actor Robin Williams abruptly postponed upcoming performances of his one-man show, "Weapons of Self-Destruction," announcing on his web site that he needs to undergo surgery for an aortic valve replacement.

The brief announcement said that Williams, who began the 80-city tour in September 2008, hopes to pick it up again in the fall. Williams, 57, is known not only for comedy but for his role in the TV show Mork and Mindy and the 1997 movie Good Will Hunting.

The aortic valve replacement surgery that Williams needs, termed "routine" by cardiac surgeons, is the same procedure that former first lady Barbara Bush underwent earlier this week.

WebMD contacted two cardiac surgeons -- neither involved in the care of Williams -- to get more information on the valve condition and what can be done.