We randomly assigned @ patients @ years of age or older , without known atrial fibrillation , who had had a cryptogenic ischemic stroke or TIA within the previous @ months ( cause undetermined after standard tests , including @-hour electrocardiography -LSB- ECG -RSB- ) , to undergo additional noninvasive ambulatory ECG monitoring with either a @-day event-triggered recorder ( intervention group ) or a conventional @-hour monitor ( control group ) .