Former Boston mayor Raymond Flynn had a defibrillator implanted on Friday after doctors at Massachusetts General Hospital determined an irregular heartbeat probably caused him to blackout before he crashed his car into a neighbor’s house in South Boston.

The irregular heartbeat would have caused Flynn’s blood pressure to drop and made him lose consciousness. Flynn, 76, experienced an “aborted sudden cardiac arrest,’’ according to a statement released on Saturday by Frank Doyle, a Flynn family spokesman.

Dr. James Januzzi, Flynn’s cardiologist, said the defibrillator was implanted “out of an abundance of caution to protect the mayor from risk of future arrhythmia,’’ or irregular heart beat, the statement said.

Flynn lost consciousness on Thursday afternoon, after returning from a workout at Boston Athletic Club. He was trying to park his car on Flint Place, the tiny street where he lives, when he suddenly crashed into a neighbor’s home.

Flynn also suffered a concussion in the crash, Doyle said.

“[Flynn] keeps telling me, ‘My God, Frank, what if I hit somebody, I could never forgive myself,’’’ Doyle said in an interview Saturday night.

Flynn is resting comfortably, and is expected to be released from Massachusetts General Hospital fairly soon, Doyle said.

Alexandra Koktsidis can be reached at alexandra.koktsidis @globe.com. Follow her on twitter @akoktsidis.