Senator John W. Warner checked into a Virginia hospital Tuesday to be under observation due to a heart condition. Last year, the 81-year-old moderate Republican underwent a non-surgical intervention after he was diagnosed with atrial fibrillation, a condition that causes irregular heartbeat.

According to a statement released by the Senator’s office he has lately experienced a return of the condition and was admitted to Inova Fairfax Hospital for a “re-evaluation and readjustment of the medications which require regular monitoring,” the statement read. On Monday, he went to his office, where he consulted with the Capitol physician and decided to check into the hospital, the Washington Post reported.

After last year’s intervention, his heart rate and rhythm have been normal for the past several months.

According to NBC, Warner’s chief of staff said that the senator is high-spirited. His daughter told News4 that her father is doing very well.

Warner is about to finish his fifth term as Virginia’s senior senator. He has declared that he is not seeking re-election to a sixth term this fall. He will be succeeded by Democratic Mark R. Warner.

According to the American Heart Association, about 2.2 million Americans have atrial fibrillation. The condition develops in 3 to 5 percent of adults over 65. If it is not treated, atrial fibrillation could result in a stroke.