Ireland flanker Chris Henry underwent heart surgery on Monday after being ruled out of rugby for the foreseeable future last week because of a blocked blood vessel in his brain.
The Irish Rugby Football Union said that a procedure to "repair a defect in his heart wall" had been performed.
"This was found to be related to his recent episode," added the statement.
The IRFU statement added that Ulster player Henry, 30, was "recovering" following Monday's operation.
Ulster's chief executive Shane Logan said that the province was now "more optimistic than we were a week or two ago" about the likelihood of Henry making a return to professional rugby.
"I think we'd be optimistic that he will make a full recovery and come back as quickly as possible," added Logan.
Bryn Cunningham, giving his first interviews since being appointed to the newly created Ulster manager's role, added that Henry's immediate priority would be "getting back to full health".
"If he gets back to playing professional rugby that will be fantastic. That's certainly what we are hoping for," added Cunningham.
|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|
Henry missed Ireland's Test against South Africa on 8 November after being taken ill on the morning of the international.
Following further tests, the Irish Rugby Football Union revealed last Monday that Henry had suffered a "temporary blockage of a small blood vessel in his brain".
The back-rower started all of Ireland's Six Nations matches this year as they clinched the title, and brought his caps haul up to 16 by playing in both summer Tests against Argentina.
With Sean O'Brien currently out of action, Henry looked to have a strong chance of holding onto his Ireland starting role next spring.
The flanker's lengthy absence will be an even bigger blow for Ulster as they attempt to regroup after their poor start to the European campaign.