DETROIT - Red Wings defenseman Jiri Fischer had another abnormal heartbeat this week and returned to the hospital for treatment.

He was released Wednesday and is to undergo further testing at the University of Michigan Medical Center in Ann Arbor, the team said.

While resting at home Monday, Fischer experienced a “brief, abnormal cardiac rhythm,” and went back to Detroit Medical Center for tests. General manager Ken Holland said doctors have told Fischer he should have no physical activity for a minimum of four to six weeks.

Fischer last week collapsed in convulsions on the bench during a game against Nashville. Team physician Tony Colucci wasn’t able to detect a pulse after Fischer collapsed, and an auto defibrillator was used on the 25-year-old Czech.

After performing CPR, Colucci said he detected a good pulse, and Fischer was taken from the arena by ambulance to Detroit Receiving Hospital. Colucci said Fischer’s heart might have stopped, but he didn’t know for how long.

Colucci said last week the defibrillator at the game indicated Fischer’s heart may have been experiencing ventricular tachycardia, a kind of racing heartbeat, or ventricular fibrillation, a heart fluttering. Both can cause death, and ventricular fibrillation is a common cause of sudden cardiac arrest.

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Fischer was diagnosed with a heart abnormality in 2002, causing him to miss two days of practice. Colucci said tests were being done to determine whether the convulsions were related to the abnormality. When the 2002 result came back, Fischer was given a stress test that he passed, and he said his heart essentially is a little thicker than normal.