Background: Oral anticoagulation (OAC) significantly reduces the risk of stroke and mortality in patients with atrial fibrillation (AF). The purpose of this dissertation was to analyze stroke patients with previously diagnosed AF and to identify the circumstances predisposing these patients to cerebral thromboembolism. 

Methods: The FibStroke registry includes 4311 patients with previously diagnosed AF, who suffered 3252 ischemic strokes, 956 transient ischemic attacks and 794 intracranial bleeds during 2003-2012. The data were retrospectively collected from four hospitals in Finland. 

Results: 1) Almost half (49.1%) of the ischemic strokes and transient ischemic attacks occurred in patients who were not using OAC. 2) In patients with paroxysmal AF, 6.4% of the strokes occurred after cardioversion of AF. Of these strokes, 78.2% occurred after cardioversion of acute AF, while 65.4% occurred to patients who were not using OAC. 3) Postoperative ischemic strokes accounted for 6.0% of all strokes in patients with AF. Previously used OAC was interrupted for 81.2% of the operations preceding ischemic stroke. Of the postoperative intracranial bleeds, LMWH bridging was used in 54.5% of the operations. 4) Mortality during the 30 days following a stroke was significantly lower in patients with paroxysmal AF compared to patients with chronic AF (10.2% vs 20.3%). 

Conclusions: A significant proportion of the strokes in patients with AF occurred in patients who had not been using OAC or who had undergone cardioversion or operation during the previous 30 days. The type of AF (paroxysmal/chronic) may be a more important prognostic marker than previously thought.