INTRODUCTION
• Atrial fibrillation is the most common cardiac arrhythmia and the most common sustained supraventricular arrhythmia, as well as a major cause of stroke and the most common cardiac arrhythmia necessitating hospitalization.
• The pulmonary veins are the primary source of atrial fibrillation triggering as there is ectopic foci found in muscular sleeves that extend from the left atrium to the proximal pulmonary veins.
• Since then, catheter ablation emerged and has proven to be an effective and safe treatment for atrial fibrillation, and it is now considered first-line therapy in some situations.
• For optimal treatment, all pulmonary veins must be ablated, so it is critical to understand the anatomy of the pulmonary veins, as well as their ostial orientation.
• The most typical pattern is four separate veins that emerge from the left atrium and have distinct ostia, however increasing research has revealed that variant morphology of pulmonary veins is prevalent, affecting 30-44 % of the population.
• Multidetector CT can evaluates the morphology and size of the pulmonary veins and Left atrium. It is also has wide anatomic field of view, which allows it to assess related lung and cardio-vascular abnormalities

AIM OF THE WORK
The aim of this study is to evaluate the role of multi-detector computed tomography in assessment of pulmonary venous abnormalities on pre-radiofrequency ablation mapping for atrial fibrillation.