How often atrial flutter and atrial fibrillation coexist? Results from a large nationwide ECG-based study

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Foundation. Main funding source(s): Sigrid Juselius foundation Finnish Foundation for Cardiovascular Research BACKGROUND: Atrial flutter (AFL) is often encountered in atrial fibrillation (AF) patients. There are many similarities in the etiology and treatment of these arrhythmias, including the need for anticoagulation for the majority, but there are also significant differences in their management. In many population-based studies AFL and AF are combined; thus, data are lacking on their individual prevalence in the general population. PURPOSE: To investigate how common are isolated AF and AFL in the population and how often these two arrhythmias coexist in a patient. METHODS: All adult patients with an ICD-10 code I48 (including AF and AFL) in Finland 2004-2017 were identified from comprehensive national registries including primary and specialist care, reimbursement registries and hospitalization records. A subset of the cohort living in a region using an electronical ECG storage system had their ECG reports produced by the ECG analysis program retrieved for the analysis. ECGs with poor quality and paced or unspecified rhythm were excluded. RESULTS: Altogether, 1,248,851 ECGs from 85,690 patients (14.6 ECGs per patient) with the ICD-10 code I48 were included. Mean age was 70.7 ± 13.1 and 53.4% were men. ECGs documenting AF/AFL were available for 67,529 patients (78.8% of the entire ECG-cohort). 51,105 of them had ECG documentation of AF only (AF-only; 53.7% male), and 13,195 (20.5%) of patients with AF had also AFL documented in the ECG (AF+AFL; 47.6% male). 3,229 (4.8% of those with AF/AFL) presented with isolated AFL (AFL-only, 63.1% male). Of the total of 16,424 patients with documented AFL, 80.3% also had AF. The rest of the subjects did not have a 12-lead ECG in the retrieved electronic records documenting atrial arrhythmia. CONCLUSIONS: One-fifth of the AF patients had also atrial flutter documented with a 12-lead ECG. Moreover, 80% of the atrial flutter patients experiences atrial fibrillation as well. These findings may have implications for the treatment and follow-up of these patients. [Figure: see text]