Galway councillor Michael "Stroke" Fahy, who was due to begin a 12-month jail sentence earlier this week, underwent a cardiac procedure in hospital yesterday.
The 56-year-old councillor was rushed to hospital on Monday night complaining of chest pains - the day before he was due to start his sentence in Castlerea Prison.
A spokesperson for University College Hospital Galway said that they did not comment on individual cases.
However, it is understood that Cllr Fahy underwent a cardiac procedure and had a stent inserted.
His condition was being monitored last night. It has not been established how long he will remain in hospital, or when he will be in a condition to commence his prison sentence.
Cllr Fahy had been due to present himself at Loughrea Garda station on Tuesday morning to begin a one-year sentence for defrauding Galway County Council.
The former Fianna Fáil councillor was also fined €75,000 when he was convicted a few weeks ago.
He was convicted by a jury of seven counts of fraud and attempted theft arising from the erection of more than a mile of fencing on his farmland by a private contractor hired by Galway County Council.
The Ardrahan-based farmer is the longest serving member of Galway County Council. He has been elected as a councillor at every local election since his first in 1979.