McIlroy said in an interview with The Telegraph that he has a thickening of the left ventricle. He says doctors told him it was caused by a viral infection he suffered in China 18 months ago.
He says he'll get an electrocardiogram every six months and an MRI once per year.
"There's a bit of scar tissue. For now, I just need to stay on top of it and have to stay fit. Hey, I was planning on doing that anyway," McIlroy said.
McIlroy said later in an Instagram post , "It's really not that big of a deal and nothing to worry about, apart from getting an annual checkup, like you should do anyway. ... I'm fit and healthy and can't wait to get my 2018 season started in Abu Dhabi next week."
McIlroy says he's fully recovered from the rib injury he suffered a year ago that contributed to a winless 2017. He finished the year ranked 11th, his worst year-end ranking since his rookie year in 2008.
McIlroy took three months off at the end of 2017 to allow his rib to heal. He plans to play eight events before the Masters, his most ambitious schedule ahead of Augusta National in the 10 years he's been eligible.Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.