Atrial fibrillation (AF) is the most common sustained arrhythmia. While the primary treatment concern with AF is the managing the risk of thromboembolism, AF can also cause significant symptoms in some patients and be completely asymptomatic in others (1). Many patients with AF have debilitating symptoms including palpitations, heart failure, and anxiety. It is well known that patients can have some symptomatic AF episodes and others that are asymptomatic (2). In this issue of the Journal of Cardiovascular Electrophysiology, a study by Ahluwalia et al. attempts to assess factors associated with symptomatic AF episodes in patients with insertable cardiac monitors (ICM).In this retrospective observational study, the authors examined 11,267 patients with a Reveal LINQTM ICM in the DiscoveryLink from 2007 to 2021. These patients all had episodes of AF detected by the ICM’s detection algorithm, and the patient’s clinical data was obtained from the Optum® de-identified electronic health record. The AF episodes were not adjudicated, and the symptoms were not verified.Asymptomatic AF was far more common than symptomatic episodes. Only 15.8% of patients had a device reported AF symptom. In addition, of the 380,625 episodes of automatically detected AF, only 6190 episodes (1.63%) had a symptom activation within 20 minutes. The symptomatic AF patients were younger (67±12 years vs. 71±11 years old), more female (51% vs 43%), and had less cardiovascular diagnoses. In addition, AF episodes with a symptom activation, were longer in duration (5.5 hrs vs. 3.7 hrs), had a higher ventricular rate (103 bpm vs. 88 bpm), and had a higher AF evidence score (more likely to be true AF per the device-based algorithm)These findings are similar to other reports about AF detections, especially device detected AF, but have extended them to a large cohort of patients with ICMs, with clinical and symptom data. The most important takeaway is that screening for AF needs to go far beyond evaluation for symptoms as most AF episodes are not symptomatic, and in patients with symptomatic AF, the episodes of AF are just the tip of the iceberg of AF burden. Symptoms were associated with a higher AF evidence score, indicating the symptoms could be used to help differentiate a true AF detection, from a false positive which could help guide clinical management. Also AF symptoms seemed to be more common in younger, less comorbid, and female patients, which is consistent with other published data (1). This does highlight one paradoxical finding, that females seem to be more symptomatic with AF, but less likely to be offered ablation.The primary limitation of this study is the retrospective observational nature of the data. It is unclear why the patients pushed the symptom activator. The symptom activation could have been for palpitations, another AF related symptoms, or purely accidental. It is not known what instructions the patients received to activate the symptom activator, and what percentage of patients knew how to actually use it properly. Also given the nature of the handheld device to mark symptoms, it is likely that many patients did not activate the ICM for every symptom either to due to symptom fatigue, or inability to access the activator at the time of an episode. Some of these limitations could be overcome with a prospective cohort educated in using the ICM to track AF symptoms, and the newer app-based symptom activators. Since the AF episodes were not adjudicated, it is unclear if some of the symptom episodes were related to false AF detections. Another useful piece of information from this data would be the number of symptom activations that were not related to an arrhythmia.However, this study does give an insight into a large cohort of patients with AF and ICMs. This data could help spur future research into how to properly assess for AF symptoms, and how to minimize AF symptoms.Sgreccia D, Manicardi M, Malavasi VL, Vitolo M, Valenti AC, Proietti M, Lip GYH, Boriani G. Comparing Outcomes in Asymptomatic and Symptomatic Atrial Fibrillation: A Systematic Review and Meta-Analysis of 81,462 Patients. Journal of Clinical Medicine. 2021; 10(17):3979. https://doi.org/10.3390/jcm10173979Quirino G, Giammaria M, Corbucci G, Pistelli P, Turri E, Mazza A, Perucca A, Checchinato C, Dalmasso M, Barold SS. Diagnosis of paroxysmal atrial fibrillation in patients with implanted pacemakers: relationship to symptoms and other variables. Pacing Clin Electrophysiol. 2009;32:91-98. https://doi.org/10.1111/j.1540-8159.2009.02181.x