Rory McIlroy says he has an irregularity with his heart, which impacted on his injury-plagued 2017.
Rory McIlroy of Northern Ireland tees off at the second hole.
He failed to win a tournament last season for just the second time in his career.
"I had an MRI scan on my thoracic spine and all was OK," he told the UK's Daily Telegraph.
"But I've got a bit of an irregularity with my heart that I have to keep on top of.
"I have a flat T-wave and I'll have to get an echo (cardiogram) on my heart every six months and an MRI scan every year.
"I suffered a really bad viral infection in China 18 months ago and they told me that's the reason that I have this thickening of my left ventricle and there's a bit of scar tissue."
McIlroy, who has slipped to 11th in the world rankings, last appeared at the Dunhill Links Championship in October and will make his return to competition at next week's Abu Dhabi Championship.