Introduction: 
Preprocedural imaging is suggested to evaluate the individual arrhythmia substrate and to guide ablation procedures in patients with atrial fibrillation (AF). The aim of this study was to investigate the prevalence and clinical relevance of incidental findings from cardiac computed tomography (CT) and magnetic resonance imaging (MRI) prior to AF ablation. 

Material and methods: 
A total of 250 patients were included in this observational single-center analysis (mean age 67±10 years; 63% male). All acquisitions were contrast enhanced using a 64-slice-Multidetector-CT (n=201 patients; 80%) or a 3-Tesla MRI (n=49 patients; 20%). All datasets were evaluated by a radiologist and a cardiologist. For additional scan interpretation different window settings were used, too. Incidental findings were categorized as significant if they led to additional diagnostics or treatment or otherwise as non-significant.

Results:
A total number of 201 incidental findings were documented in 194 patients (77.6%). Thereof, 57 patients (28%) have had at least one clinical significant finding, including 16 patients with a malignant finding. The remainder (n=144; 72%) were classified as patients without a significant finding. Incidental findings in our AF patient cohort were revealed in the lungs (n=71 findings; 35.3%), the abdomen (n=61 findings; 30.3 %), the musculoscelettal system (n=49 findings; 24.4%) and the mediastinum (n= 20 findings; 10%).

Conclusion: 
Incidental findings are common bycatch from preprocedural imaging in patients prior to AF ablation. Interdisciplinary trained personnel is required to identify and judge both cardiac and extra cardiac findings in terms of clinical relevance. Preprocedural imaging led to additional diagnostics and therapy in nearly a third of patients including life-threatening malignancies. Due to their potential clinical significance, all images should be evaluated with an emphasis on incidental findings prior to ablation.