In patients with symptomatic atrial fibrillation rates of spontaneous conversion are high.1-3 In real-world emergency cohorts optimal management is unclear; however, treatment with early cardioversion is a common practice, although the individual probability of a patient converting to sinus rhythm spontaneously is uncertain. Deferred cardioversion in patients with a low probability of spontaneous conversion may result in an unjustified treatment delay and increased risk of stroke, heart failure and progression to persistent atrial fibrillation,4-6 Conversely, patients who are likely to convert to sinus rhythm spontaneously, but undergo early pharmacological or electrical cardioversion may be unnecessarily hospitalized and exposed to the risk of post-conversion arrhythmias and complications by general anesthesia or antiarrhythmic drugs.