World number 11 Rory McIlroy revealed he had an "irregularity" with his heart that he would need to manage.
The Northern Irishman finished 2017 without a win – the first time he had failed to claim a tournament in a calendar year since 2008.
While McIlroy battled injuries last year, the 28-year-old revealed he also had a heart problem that he needed to keep an eye on.
"The rib's fine, no problems whatsoever – I had an MRI scan on my thoracic spine and all was OK. But I've got a bit of an irregularity with my heart that I have to keep on top of," he told The Telegraph.
"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.
"For now, I just need to stay on top of it and have to stay fit. Hey, I was planning on doing that anyway."
A four-time major winner, McIlroy claimed the most recent of those at the 2014 US PGA Championship.
While he has slipped outside the top 10 in the rankings, McIlroy said his focus was purely on winning.
"It's nice to be world number one, sure, and I will get back there, but it's all about winning tournaments," he said.
"And I will give myself the best chances this season."
|Impressive Halep cruises past Pliskova|
|Spurs spoil LeBron´s 30,000th-point celebration|
|Westbrook says George should be All-Star|
|Chung continues dream Australian Open run|
|Keys unhappy with quarter-final display|
|Kerber full of confidence in Melbourne|
|Neymar is loved by PSG fans – Emery|
|LeBron James becomes youngest NBA player with 30,000 points|
|NBA All-Star Game reserves leaked ahead of announcement|
|Kerber crushes Keys to reach Aus Open semis|
|Serena Williams set to make competitive return in Fed Cup|
|Heat guard Waiters undergoes season-ending ankle surgery|
|Simeone shoulders blame for Atletico´s Copa exit|
|Wenger: Sanchez not a mercenary for joining Manchester United|
|Phil Neville deletes Twitter account after controversial posts surface|
|Sam Curran added to England T20 tri-series squad|
|Guardiola: Quadruple-chasing City will only be judged on trophies|
|Karsiyaka and Nymburk reach FIBA Champions League last 16|
|Batshuayi out of chances to convince Conte|
|Chelsea lacked finances to compete with City & United for Sanchez - Conte|
|Sevilla 3 Atletico Madrid 1 (5-2 agg): Griezmann stunner not enough for semi spot|
|Bristol City 2 Manchester City 3 (3-5 agg): Guardiola through to first English final|
|Serena can return for more grand slam success – King|
|O´Neill signs Ireland extension|
|Teachers bowled over by Edmund ability|
|Woods grouped with Reed and Hoffman at Torrey Pines|
|New signing Jach sees Palace as platform for World Cup spot|
|Thomas replaces Sinckler in England training camp|
|Phil Neville appointed England Women´s manager|
|Heat unveil Miami Vice-themed uniforms|
|Kenedy leaves Chelsea for Newcastle loan|
|Wozniacki still haunted by 2011 Li Na loss|
|PSG rule out ´traumatic´ injury for Mbappe|
|PSG boost midfield options with surprise Diarra signing|
|Dyche commits to Burnley to 2022|
|Patriots elect to wear white in Super Bowl LII|
|Kobe Bryant´s ´Dear Basketball´ short film nominated for Oscar|
|Zidane tells Real Madrid fans to stop jeering Benzema|
|Players must manage their own schedules, says Cilic|
|Lucas Moura free to leave PSG, confirms Emery|
|Kenedy set for Newcastle as Conte waits for window to close|
|Bouchard agrees to another Super Bowl date|
|Neymar and Mbappe in doubt for PSG´s clash with Guingamp|
|Targeting the backhand, attacking the net and 83 winners: How Cilic subdued Nadal|
|Mascherano to leave Barcelona as Hebei move looms|
|Wozniacki reaches Australian Open semi-finals in early hours|
|Conte rules Morata and Fabregas out of Arsenal clash|
|Tamim and Shakib leave Zimbabwe facing tri-nation exit|
|Clarets snap up Lennon from Everton|
|Too many people are getting injured - Nadal frustrated by Aus Open retirement|
|Dzeko set to face Sampdoria despite Chelsea reports|
|It´s really unfortunate for Rafa - Cilic sympathises with injured Nadal|
|Zidane rejects suggestions he won ´battle´ over Kepa|
|Surprise semi-finalist Mertens ready for more Melbourne magic|
|Sorry Stars fail to shine again as Sixers claim consolation win|
|Injured Nadal bows out of Australian Open to Cilic|
|Ramos trains for Real Madrid as wounded Ronaldo works indoors|
|Wijnaldum admits Liverpool ´gave a half away´ against Swansea|
|I know what it feels like to be Andy Murray - Edmund revels in limelight|
|Wenger: Arsenal are about values, not millions|
|Gracious Dimitrov says Edmund deserved to win|
|Aubameyang to Arsenal not close, says Wenger|
|Hernandez open to West Ham exit|
|Superstar Sanchez will lift Manchester United squad, says Giggs|
|De Bruyne 2023: The sensational displays that won Manchester City´s talisman a new deal|
|How new recruit Sanchez compares to Manchester United´s forwards|
|Edmund claims shock win over Dimitrov to reach Aus Open semis|
|Cousins posts one of greatest stat lines in NBA history|
|Rockets close gap on Warriors by beating Heat|
|Lucas ´not happy´ at PSG|