Sen. Barbara Mikulski (search) was released from a hospital Friday after being diagnosed with an irregular heartbeat, her office said.

Mikulski, the most senior woman in the Senate and a member of the Senate Appropriations Committee, was diagnosed with atrial fibrillation (search), an irregular beating of the upper chambers of the heart.

The common condition affects more than 2 million people in the U.S. and is treated through medication.

The four-term Maryland senator was admitted to Mercy Hospital on Monday, complaining of fatigue. Mikulski, 68, will be able to maintain her usual schedule, her office said in a statement.

"I have thought a lot in recent days about how fortunate I am to have this quality of care," Mikulski said. She said she was eager to get back to work "to continue my fight to ensure that all Americans have access to the best possible health care (search)."