American Mardy Fish has been ruled out of the Australian Open as he continues to recover from a series of health issues.

The 30-year-old had an operation in May to correct a form of arrhythmia in his heart, but it is understood that he will not be available for the first Grand Slam of the year.

"The good news is that Mardy's health is improving and he is back on the court slowing getting back into his regular workouts," Fish's agent John Tobias told Reuters.

Fish, whose ranking has fallen from eighth to 27th, has not played since the US Open in September.