Charlie Beljan justified his decision to ignore medical advice by maintaining his lead at the Children's Miracle Network Hospitals Classic in Florida.
Beljan was hospitalised overnight after complaining of shortness of breath and an elevated heart rate during his second round, in which he struck a magnificent eight under par 64 to move to the top of the leaderboard.
"I thought I literally had a chance to die," he told the PGA Tour website.
Doctors recommended the 28-year-old American withdraw from the tournament this morning as a precautionary measure but Beljan opted to continue and his 71 helped him move to 13 under par overall - two shots clear of compatriots Brian Gay and Josh Teater and South Korean Charlie Wi.
Beljan, who believed he may have suffered a panic attack yesterday, said: "I honestly didn't know if I was going to play one hole, any holes or was I going to get through the day.
"I felt good, better as the day went on, and I just hung tough, hung in there."
Beljan could reap the benefits of his decision to play on. Ranked 139th on the money list at the start of the week, he is one of a number of players scrambling to be in the top 125 at the end of the tournament to keep his tour card.
"I knew what the rewards were at the end of the week if I could pull something off, and that's kind of what kept me going," he said.
"The position I'm in, it's kind of hard not to show up."
It seemed likely his challenge would fade when he bogeyed two of the first three holes but he picked up a shot on the par five fourth and further birdies on the seventh, 10th and 11th helped reignite his challenge.
He carded his third bogey of the day on the next before safely negotiating the final six holes.
The 17th and 18th proved tricky, in particular, for both Gay and Wi, both of whom would be sharing the lead alongside Beljan had they both not recorded back-to-back bogeys.
Gay seemed certain to finish strongly after five consecutive birdies from the 10th but his challenge stalled and he was forced to settle for 67, the same as Teater.
Wi, overnight leader after the first day, endured mixed fortunes with six birdies and four bogeys while former two-time Ryder Cup representative Henrik Stenson was among seven players in a tie for fifth on 10 under overall.