Objective To identify the risk factors of thromboembolism related to atrial fibrillation (AF) in difference structural heart disease and prevention of thromboemboembolism with warfarin.

Methods 285 consecutive cases with AF, of which 110 were rheumatic heart disease (RHD), and 57 received prosthetic heat valve, and 53 received medicine therapy; of which 67 were hypertension; of which 35 were patients without structural heat disease; of which 26 were patients with sick sinus syndrome who are receiving a pacemaker for symptomatic bradycardia of which 16 were ischaemic heart disease; of which 15 were dilated cardiomyopathy; of which 10 were congenital heart disease; of which 8 were other disease. Clinical data including gender; age; incidence of left atrial (LA) thrombus; incidene of thromboembolism or history of stroke or transient ischaemic attack (TIA); incidence of using warfarin and dose of warfarin; events of death.

Results Incidence of left atrial (LA) thrombus (21.8%) and incidence of thromboembolism or history of stroke or transient ischaemic attacck (TIA) (9.1%) in RHD group were significantly higher than those in other group (0–4%) (p<0.001); incidence of using warfarin in RHD group (94.5℅) were significantly higher than those in other group (61.7%) (p<0.05).

Conclusion Antithrombotic therapy is key and essential treatment in AF with one high or two moderate risk factors. RHD and prosthetic heart valve is high risk factor of LA thrombus and thromboembolism. 7 patients of AF with hypertension and ischaemic heart disease have thromboembolism, but only one patient by transthoracic echocardiography (TTE) have LA thrombus. So transesophageal echocardiogram is done. AF in whom anticoagulation is indicated to use warfarin. The target International Normalised Ratio (INR) range is 2.0–3.0, but while combination of warfarin and amiodarone the dose of warfarin is less than average dose.