Eligible patients with paroxysmal or persistent NVAF , a left ventricular ejection fraction > 40 % , and a creatinine clearance > 50mL/min will be randomized 1:1 to rivaroxaban 20mg orally once daily or to dose-adjusted oral VKA ( recommended international normalized ratio ( INR ) 2.0-3 .0 ) and stabilized on anticoagulation therapy for 1-7days ( if no intracardiac thrombus on transesophageal echocardiogram ( TEE ) immediately prerandomization/post-randomization or if 3weeks of sufficient anticoagulation is documented ) or for 4-5weeks ( if no TEE , no documented 3weeks of sufficient anticoagulation , or by patient choice ) .