Objectives: To investigate arrhythmias in patients with primary chronic mitral regurgitation by using a 24 - hour ECG Holter and to evaluate the association between arrhythmias and the degree of mitral valve regurgitation, left atrial diameter, degree of NYHA, left ventricular ejection fraction (LVEF%). Methods: A cross - sectional descriptive study of 48 patients diagnosed with chronic mitral regurgitation with valvular involvement lesions such as rheumatism or prolapse valve at the Department of Internal Cardiology of Hue Central Hospital from 4/2021 - 4/2022. Results: The mean age of sample was 58.19 ± 16.46 years, women accounted for 64.58%. Among patients who had arrhythmias with 24 - hour Holter ECG monitoring, the majority were atrial fibrillation (58.30%), followed by premature ventricular complex (54.20%) and premature supraventricular complex (16.70%). The incidence of atrial fibrillation increased when the degree of mitral regurgitation was heavier, and the group had a left atrial diameter of >
45 mm (p <
0.05). The incidence of atrial fibrillation varies between levels of heart failure according to the NYHA (p <
0.05). Meanwhile, there was no difference in the incidence of atrial fibrillation between the two groups, EF <
50% and EF ≥ 50%. When analyzing multivariate logistic regression, age (OR = 1.062, 95% CI: 1.005 - 1.121) and left atrial diameter (OR = 1.181, 95% CI: 1.033 - 1.349) are prognostic factors for atrial fibrillation in patients with chronic mitral regurgitation. Conclusions: Cardiac arrhythmias are a common complication in patients with chronic mitral regurgitation. Atrial fibrillation remains the most common arrhythmia. Age factors and left atrial diameter are 2 factors that increase the likelihood of atrial fibrillation in these patients.