Ireland flanker Chris Henry was left "terrified" after suffering a mini-stroke hours before last month's Test against South Africa.
The Ulster back row underwent heart surgery last week after a small hole was discovered in the organ.
In his first interview since the operation, the 30-year-old revealed he lost strength in an arm and one side of his face during the episode.
"It was terrifying," he said. "I was preparing for the worst at stages."
However, after four days of treatment at St Vincent's Hospital in Dublin, it emerged he had suffered a Transient Ischaemic Attack - known as a mini-stroke - because the hole in his heart had led to a blocked blood vessel in his brain.
|Chris Henry factfile|
|1984: Born, 17 October, Belfast|
|2003: Ulster Schools and Irish Schools captain|
|2004: Played for Ireland in U20 World Cup|
|2008: Ulster senior debut|
|2010: Ireland Wolfhounds skipper, first Ireland cap and Ulster player of year|
|2012: Helps Ulster reach Heineken Cup final|
|2014: Part of Ireland's Six Nations Championship winning team|
"The doctors have been able to get in there and fix the problem and for me to have that clarity, I feel so lucky," he added.
"I was lucky to have such incredible medical expertise around me after I was taken straight to St Vincent's on the Saturday."
Henry revealed that his room-mate and fellow Ireland player Rhys Ruddock came to his aid, ensuring a doctor was by his side within three minutes of the incident.
"Rhys Ruddock was able to help me fortunately," he added. "If it had happened anywhere else, I'm sure it would have been a lot more frightening."
Ruddock was then drafted into the Ireland team as Henry's replacement for the Springboks clash and went on to score a try in the surprise 29-15 win.
Henry acknowledged his initial fear was that his career might be over. But now he is aiming to reclaim his Ireland place for next year's World Cup.
"I think that is a realistic target," he said. "In my mind, I want to be back by the end of this season. Whether that is pushing it too much, we'll just have to wait and see."
Henry rejoined his Ulster team-mates at Kingspan Stadium on Monday, doing a short spin on an exercise bike a week after his surgery.
"I'm just delighted to come back in and be amongst the players and the team environment."
Henry adds that he has been "overwhelmed" by the messages of support from Ulster and Ireland team-mates and from the rugby world and wider community.
Henry's Ireland colleague Richardt Strauss was also diagnosed as having a hole in his heart in October 2013. He was able to resume his career three months later.