The 28-year-old revealed in an interview with the Daily Telegraph that the condition may be linked to a viral infection he contracted 18 months ago.
The former world number one, who has four majors on his CV already, has made it clear that he is fully fit and raring to go after failing to win a tournament anywhere in the world last year.
He struggled with injury in 2017 and cut short his schedule in order to undergo treatment on a rib injury but is now ready to kick off his season in the UAE after playing down the recent health scare.
"Yesterday I did an interview with the Daily Telegraph where I spoke about a range of topics regarding the last three months of my life," he said on Instagram.
"I touched upon a recent finding from a routine health and wellness check. Like anything, the deeper you dig the more likely you are to find something.
"It revealed I had a slight heartbeat irregularity called a flat or inverted T wave. It's really not that big of a deal and nothing to worry about, apart from getting an annual check-up, like you should do anyway.
"I feel there's been a big reaction to it in the media which there really shouldn't be. I'm fit and healthy and can't wait to get my 2018 season started in Abu Dhabi next week."