The primary aim of this study is to determine the safest and most effective therapeutic strategy to decrease the incidence of postoperative atrial fibrillation following cardiac surgery in an era with shorter ICU and hospital length of stay. A secondary goal is to evaluate the length of hospital stay associated with each treatment strategy.

Inclusion Criteria:

• age > or = to 18 years
• sinus rhythm
• undergoing either coronary artery bypass graft surgery (CABG), valvular heart surgery or a combined procedure

Exclusion Criteria:

• received a class-I or class-III antiarrhythmic agent in the past six months
• had second or third degree heart block
• had a resting heart rate of less than 50 beats per minute
• had a systolic blood pressure less than 100 mmHg
• had severe asthma or severe chronic obstructive pulmonary disease
• had uncontrolled heart failure
• had a serum aspartate aminotransferase or alanine aminotransferase concentration greater than four times the upper limit of normal

adult patients undergoing open heart surgery