Sen. John Warner, R-Va., has been hospitalized with an abnormal heart beat, but his office downplayed the seriousness of his condition.

Warner, 81, was treated last fall for atrial fibrillation — or an irregular heartbeat — which his office characterized on Tuesday as "a common condition."

Warner's office released a statement saying the senator sought a medical consult Monday for return of his symptoms and stayed overnight at a Virginia hospital.

"Yesterday, Senator Warner came to his office, consulted with the Capitol Physician, completed his office appointments and left for a scheduled admission to Inova Fairfax Hospital, where he remains for observation," according to a statement from his office released Tuesday.

Warner's office downplayed the development, saying he was "pursuing a re-evaluation and readjustment of medications which require regular monitoring and observation within a hospital environment."

The statement did not say when the senator is expected to be released.

Symptoms of atrial fibrillation include heart palpitations, lack of energy, dizziness, chest discomfort and shortness of breath, according to WebMD.com.

It can be caused by high blood pressure, coronary artery disease, heart valve disease, previous heart surgery, chronic lung disease, heart failure, cardiomyopathy, congenital heart disease or pulmonary embolism, according to WebMD.com.

Warner, a moderate Republican, has said he will not seek a sixth term this fall.

Click here to read more about atrial fibrillation at WebMD.com.