OBJECTIVE Maintaining sinus rhythm is important in the management of atrial fibrillation (AF). After cardioversion, there is a significant probability of AF recurrence. There is limited research on the relationship between AF recurrence and ECG parameters. This study aimed to evaluate whether the frontal plane QRS-T angle (fQRS-T), a predictor of ventricular heterogeneity, could be used to predict AF recurrence following cardioversion. METHODS The study was conducted as a retrospective observational study. Patients diagnosed with acute-onset AF for the first time were included in the study. All patients underwent an ECG after cardioversion, and ECG parameters were evaluated. The patients were separated into two groups based on the presence of AF recurrence during hospitalization after cardioversion. The relationship between the fQRS-T and AF recurrence was also examined. RESULTS A total of 162 patients, comprising 68 women (41.9%) and 94 men (58.1%) with an average age of 59.4±6.5 years, were enrolled in the research. Based on the patient monitoring device findings, patients were separated into two groups: non-recurrent AF (n=118) and recurrent AF (n=44). P-wave duration was significantly longer in the recurrence group (p=0.009). The recurrence group's mean fQRS-T was significantly higher (p<0.001). AF recurrence was substantially higher in patients with fQRS-T >90 ° compared to those with fQRS-T ≤90 ° (56.1% vs. 14.2%, p <0.001). Increased fQRS-T>93.7 ° indicated AF recurrence with 78.3% sensitivity and 83.4% specificity (AUC {area under curve}:0.748, p < 0.001). In multivariate analysis, fQRS-T was revealed to be an early indicator of recurrent AF (OR: 1.882, 95%CI: 1.358-2.881, p<0.001). CONCLUSIONS The fQRS-T, an easily determinable parameter from automatic identification ECG recordings, may be useful for predicting the early return of AF after successful cardioversion.