Background: Major gaps exist in the evidence for predicting optimal patient outcomes of cardioversion (CV) in atrial fibrillation (AF). The aim of this dissertation was to assess the safety and efficacy of elective CV in AF.

Methods: The Finnish Cardioversion study programme (FinCV) investigates the occurrence of stroke and procedural efficacy in AF patients undergoing CV. Studies included patients undergoing acute CV (FinCV), elective CV in vitamin K antagonist treated patients (FinCV2) and non-vitamin K antagonist treated patients (Fin-CV3). The patients' data were retrospectively collected during the 2003–2016 timeframe from nine Finnish hospitals. Altogether, the FinCV studies comprised 5441 patients and 10852 CVs, of which the FinCV2 study encompassed 1342 patients with 1998 elective CVs.

Results: Elective CV was unsuccessful or AF recurred within the 30-day follow-up after an initially successful CV in 42.6% (FinCV2). Altogether, 6 (0.4%) cerebral thromboembolisms were detected within follow-up and patients with low (2.0–2.4) therapeutic internationalized normalized ratios (INRs) at the time of elective CV had a higher risk for thromboembolic events than patients with high (≥2.5) therapeutic INRs (0.9% vs. 0.1%, p=0.03) (FinCV2). In the combined registry of the FinCV studies the primary composite end-point was designated as an occurrence of death, thromboembolism, unsuccessful CV, recurrence of AF or acute arrhythmic complication within follow-up. The composite adverse outcome was observed after 1669 (38.4%) CVs and patients with AF episodes lasting 24–48 hours had the lowest risk of adverse outcomes.

Conclusions: The intensity of anticoagulation in elective CV of AF is associated with the risk of postprocedural thromboembolisms. Nevertheless, CV in AF has relatively few safety issues, although more room exists for improvement in efficacy outcomes of CV in contemporary medicine.