Doctors are working to determine if he suffered any brain damage due to the heart attack and subsequent lack of oxygen to his brain.
They added, Rivera has showed signs of improvement but still remains in critical condition.
Manny Rivera has been fighting fires in Trenton for nearly 14 years.
The Monday night fire happened at 112 Washington Street.
Rivera had just pulled a fire victim, who was hanging out of a window, down a ladder to safety.
When he reached the ground he passed the victim to ambulance workers, then collapsed.
He is a married father of five children.
Two occupants of the burning home were hurt, but not seriously injured.
The cause of the fire has been ruled accidental.
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