Patients were divided into two categories according to the congestive heart failure , hypertension , age 75 years , diabetes and prior stroke [ or transient ischaemic attack or thromboembolism ] ( CHADS2 ) score : 60 patients were assigned to the high-risk group ( CHADS2 score 2 ) and 55 to the low-risk group ( CHADS2 score 1 ) .