Atrial fibrillation (AF) is the most frequent cardiac arrhythmia and the number of patients with AF will increase within the next years as the population ages. Different forms of AF (i.e. paroxysmal, persistent and permanent) confer a similar stroke risk and furthermore AF accounts for every fifth ischemic stroke in Germany. Patients with AF-related cardio-embolic strokes show a poorer prognosis and a higher recurrence rate compared to strokes of other etiologies. Long-term oral anticoagulation with vitamin K antagonists (VKAs) reduces the risk of recurrent stroke in AF patients by about two thirds compared to placebo and is substantially more effective than acetylsalicylic acid. It emerges that new oral anticoagulants (NOACs) such as dabigatran, rivaroxaban or apixaban are at least as effective or even more effective compared to the VKA warfarin for the prevention of recurrent stroke, (intracranial) bleeding and death. National and international guidelines recommend oral anticoagulation for patients with AF and prior ischemic stroke with the highest level of evidence.

The detection of paroxysmal, so far undetected ("silent") AF represents a major diagnostic challenge in patients with acute ischemic stroke, remaining undetected in a relevant proportion of stroke patients. However, prolonged (post-hospital) ECG monitoring and systematic analysis of ECG recordings enhances detection of non-permanent AF after ischemic stroke, but optimal length of monitoring remains unclear. Moreover, implantable cardiac-event recorders increase AF detection rates in selected stroke cohorts, but are invasive and expensive, not supporting routine use. As most of the published ECG data are taken from single-center studies, current stroke guidelines do not recommend prolonged ECG monitoring and do not specify the requirements for ECG analysis in stroke survivors. Subsequently, there is no common practice or "gold standard" of ECG monitoring in most healthcare systems, as well as in the German stroke unit system. This fact likely results in an important under-diagnosis of AF in stroke survivors. A systematic assessment and randomized comparison of the diagnostic yield and therapeutic impact of prolonged ECG monitoring for silent AF in stroke survivors would have immediate impact on patient management, as oral anticoagulation would only be prescribed to optimize secondary stroke prevention after ischemic stroke or TIA when AF has been documented. Moreover, a standardized prolonged continuous ECG monitoring will help to clarify the clinical relevance of short-lasting atrial runs (<30 s and ≥ 6 conducted premature activations; so called "paroxysmal short atrial tachycardia"), a common finding in stroke patients. According to US claims data, paroxysmal short atrial tachycardia was independently associated with a twofold higher risk of subsequent stroke. In addition, the Copenhagen Holter Study demonstrated that excessive supraventricular ectopic activity was associated with an almost threefold risk of hospital admission due to AF or ischemic stroke. Nevertheless, paroxysmal short atrial tachycardia as well as excessive supraventricular ectopic activity is not defined as (paroxysmal) AF and therefore, there is no indication for the prescription of oral anticoagulants according to guidelines. Taken together, well-designed large prospective, randomized, multicenter studies are urgently needed to clarify these major issues of stroke prevention and will help to optimize the use of VKAs and NOACs. The proposed MonDAFIS study will help to define the optimal duration and modality of ECG recording after ischemic stroke or TIA and could change the diagnostic workup for stroke patients in Germany and throughout Europe.