BOSTON — The death of the father of Olympic skater Nancy Kerrigan was ruled a homicide today when an autopsy showed he died of a heart rhythm problem after a fight with his son in which he suffered a neck injury so severe it damaged his windpipe.

The findings could prompt new charges against Kerrigan's brother, Mark, who has pleaded not guilty to assault and is undergoing a psychiatric evaluation.

Daniel Kerrigan, 70, died Jan. 24 after what authorities said was a struggle with his 45-year-old son, Mark.

Police say Mark Kerrigan told them he put his hands around his father's neck and his father fell to the floor after the two argued at their Stoneham home.

Family members had initially said Daniel Kerrigan had a heart attack and his death was unrelated to the argument.

The autopsy report released Tuesday by Middlesex District Attorney Gerry Leone said the elder Kerrigan also had underlying health conditions, including high blood pressure and clogged heart arteries.

"As a result of these conclusions of the medical examiner, the investigation into Daniel Kerrigan's death, and whether any charges in connection with his death are appropriate, remains ongoing," Leone said in a statement.

The findings imply a strangulation-type injury in a man already weakened by high blood pressure and clogged heart arteries, said an expert not connected with the autopsy, Dr. Ian Paul, associate medical examiner for the state of New Mexico.

"The assault itself would have caused significant physiological stress," Paul said. "It would have put direct stress to the heart itself because the heart is working faster, and in somebody with underlying heart disease, they would be at a much greater risk of experiencing sudden cardiac death."

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AP Medical Writer Marilynn Marchione in Milwaukee contributed to this report.