Background: In addition to stroke prevention with oral anticoagulation (OAC), comprehensive management of atrial fibrillation (AF) involves several important aspects. The aim of this thesis is to bring new and practical information on AF management to guide clinicians in challenging situations. Unsuccessful electrical cardioversion (ECV), excessive warfarin anticoagulation (EWA) during warfarin treatment and the limitations of CHA2DS2-VASc and HAS-BLED scores in risk stratification are the specific clinical challenges addressed in this thesis. 

Methods: The studies are based on three distinct datasets, all collected retrospectively by reviewing patient records. The FinCV (study I) data included 5,713 ECVs in 2,868 patients from two university hospitals and one central hospital in Finland during 2003-2010. The EWA Study data (studies II and III) included all patients on warfarin for AF, from 2003 to 2015 in the Turku University Hospital region, who suffered an EWA episode (defined as INR ≥9). The FibStroke data (study IV) was collected at four hospitals in Finland. All patients with a diagnosis of AF / Atrial flutter and either an ischemic stroke or an intracranial bleed between the years 2003–2012 were included. 

Results: 1) A scoring system was created to predict unsuccessful ECV. The predictive score parameters were Age, not the First AF, Cardiac failure, Vascular disease, and Short interval from previous AF episode (AF-CVS). 2) A total of 412 patients with EWA were identified, of whom 25.5% suffered a bleed. Of the many observed predictors of EWA, the strongest were alcohol abuse and impaired renal function. 3) Of the 412 EWA episodes, non-bleeding symptoms were recorded in 40.0% of patients and in 34.5% the EWA was a coincidental finding without symptoms. The 30-day mortality rate was high (9.2% to 32.7%). 4) Ischemic strokes occurred more often than intracranial bleedings in patients on OAC in each (CHA2DS2-VASc and HAS-BLED) score category, except HAS-BLED score >4. 

Conclusions: The risk of ECV failure and early recurrence of AF can be predicted with simple clinical characteristics. EWA can be predicted with several risk factors, many of which are modifiable. Bleeds are not the major determinant of the poor prognosis of EWA, as coincidental INR ≥9 findings also associate with high mortality. In patients with AF, ischemic strokes are more common than intracranial bleedings irrespective of CHA2DS2-VASc score, HAS-BLED score ≤4, or use of oral anticoagulation.