There are few large studies on which factors are associated with the occurrence of arrhythmias. Implantable loop recorders (ILR) are useful in detecting arrhythmia due to prolonged and continuous ECG monitoring. Therefore, the aim of this study is to identify and evaluate clinical characteristics and ECG parameters for predicting arrhythmias requiring pacemaker/ICD implantation by analyzing a study cohort with ILR.This bicentric study comprised a study cohort of 451 patients (mean age 64 ± 16 years, 209 women) receiving ILR implantation between 2011 and 2021. Patients were followed up on a 3 monthly outpatient interval. All arrhythmias with a pacemaker or ICD indication were considered clinically relevant. The primary study endpoint was the detection of clinically relevant arrhythmia.During a follow up of 678 ± 392 days, a clinically relevant arrhythmia was detected in 81 of 451 patients (18%). Multivariate analysis revealed five independent risk factors: coronary artery disease (HR 1.954, CI 1.077-3.546, p = .028), atrial fibrillation (HR 2.253, CI 1.201-4.228, p = .011), previous syncope (HR 6.404, CI 3.202-12.808, p .001), right bundle branch block (HR 4.370, CI 2.215-8.621, p .001) and left bundle branch block (HR 2.685, CI 1.116-6.461, p = .028). Our risk model, based on these independent predictors, divided the study cohort into patients with low (2%), intermediate (18%), medium (34%), and high (45%) risk for clinically relevant arrhythmia.By the use of ILR, a clinically relevant arrhythmia has been detected in almost one fifth of the study cohort. In addition, clinical and electrocardiographic parameters were shown to be suitable predictors of clinically relevant arrhythmia.