ObjectivesTo investigate the characteristics of new-onset atrial fibrillation (AF) and its impact on prognosis in acute pulmonary embolism (aPE).DesignA retrospective cohort studySettingThe study cohort included patients diagnosed with aPE who were admitted to the Renmin Hospital of Wuhan University from January 2017 to January 2019.ParticipantsPatients were ≥18 years of age and hospitalised for aPE.Outcome measuresAF was diagnosed based on an ECG recording or a Holter monitor during hospitalisation. aPE was diagnosed by CT pulmonary angiography. The prescription was determined from the discharge medication list. All-cause mortality was observed after 6-month follow-up. The logistic regression model and Cox proportional hazards model were used to study the risk factor of the new-onset AF and the predictor of all-cause mortality, respectively.ResultsA total of 590 patients with aPE were enrolled, 23 (3.9%) in the new-onset paroxysmal AF group, 31 (5.3%) in the new-onset persistent AF group and 536 (90.8%) in the sinus rhythm (SR) group. The incidence of the new-onset AF was 9.2% (54/590). A significant difference in age, heart rate, cardiac troponin I ultra, amino-terminal pro-brain natriuretic peptide, D-dimer, left atrial diameter, left ventricular ejection fraction, pulmonary infection, venous thromboembolism, congestive heart failure, chronic cor pulmonale and ischaemic heart disease was found among the three groups (p<0.05). Risk factors for the new-onset AF were massive PE, ischaemic heart disease and congestive heart failure. The survival rate of the paroxysmal and persistent AF group was significantly lower than that of the SR group within 6 months (60.9% and 51.6% vs 88.8%, p<0.001). New-onset persistent AF (OR 2.73; 95% CI 1.28 to 5.81; p=0.009) was an independent predictor affecting the 6-month survival in aPE patients.ConclusionsMassive PE, ischaemic heart disease and congestive heart failure are high-risk factors which were related to new-onset AF in aPE. New-onset persistent AF was an independent predictor for 6-month all-cause mortality in PE patients.