Piri Weepu has a hole in his heart, the most likely cause of the clot which caused him to have a stroke.
A scan revealed the condition yesterday and the 30-year-old is likely to undergo minor surgery to correct it.
A Blues spokesman said team doctor Stephen Kara would talk to a specialist next week about the next steps in the halfback's recovery.
However the former All Black is expected to be able to resume his playing career.
When the dramatic news was announced this week, Kara said a heart issue was the most likely cause of Weepu's stroke, which he believed happened on March 1, the day after the Blues v Crusaders match and the day Weepu flew with the team to South Africa.