Robin Williams has been forced to put the rest of his one-man tour on hold after learning he must have an aortic valve replacement operation.
Robin Williams is to undergo heart surgery.
The US comedian was admitted to a south Florida hospital - believed to be University of Miami/Jackson Memorial Medical Center in south Miami - after experiencing shortness of breath this week and his representative has now confirmed he will need an operation to correct his condition.
The representative said: "Robin is to undergo surgery for an aortic valve replacement."
The 57-year-old star - who is currently completing an 80-date tour of his one-man show 'Weapons of Self-Destruction' - was forced to pull out of four performances just a few days ago.
The rest of the tour has been put on hold.
He said in a statement: "I'm so touched by everyone's support and well wishes. This tour has been amazing fun and I can't wait to get back out on the road after a little tune-up."
Robin is believed to be in intensive care after undergoing "cardioversion" to cure an abnormal heart rhythm.
The aortic valve helps blood flow from the heart to the rest of the body.
Stanford University Medical Center says surgery takes place to "repair or replace an aortic valve that isn't working correctly. When heart valves fail to open and close properly, the heart can become damaged. Heart valve problems are one cause of heart failure".
Robin has previously battled cocaine and alcohol addiction.
In the 80s he entered rehab to beat his drug problems. He most recently checked into a facility in 2006 after relapsing.
After completing his treatment he moved into an apartment with a sober sponsor to ensure he didn't return to his old drinking habits.
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