The percutaneous invention of the catheter tip into heart chambers through an artery or vein is invasive and poses potential risks of infection and damaging blood vessels or normal heart tissue. The anterior aspect of the esophagus is always in direct contact with the posterior wall of the left atrium. A recent study found that high intensity focused ultrasound could create precise defects in different cardiac tissues without damage to the surrounding tissue. So we hypothesize transesophageal high intensity focused ultrasound ablation of left atrium posterior wall is a good noninvasive method for treating atrial fibrillation.