"Friends, unfortunately my health won't allow me to compete this year at the US Open," Fish tweeted Wednesday. "Thank you for all your support."
Fish first developed heart problems last year, experiencing an accelerated heartbeat in March 2012. Fish underwent testing and had a catheter ablation to fix faulty electrical pathways to the heart on May 23.
He was able to return to the tennis court for the 2012 Wimbledon and the US Open, but was forced to withdraw before the fourth round, citing "precautionary measures" on doctor's orders.
Earlier this month, Fish opened up about the difficulties he's faced in the past two years.
"I struggled mightily during the US Open last year. So those sort of post-traumatic experiences that I've had -- that I have now -- are what I need to get over right now," he said, adding that he considered retirement on several occasions.
"But it's a process. It's not an easy game. And fitness is as big a part of it as playing, and sometimes that's trouble -- spells trouble -- for me."
Friends, unfortunately my health won't allow me to compete this year at the US Open. Thank you for all your support.— Mardy Fish (@MardyFish) August 21, 2013