Atrial fibrillation is the common sustained cardiac arrhythmia. Risk factors for atrial fibrillation include hypertension, diabetes, valvular and other types of structural heart disease. Echocardiographic variables including left atrial enlargement, increased left ventricular wall thickness, and reduced left ventricular fractional shortening are predictive of risk for atrial fibrillation. We experienced a case of newly developed hemodynamically unstable atrial fibrillation after induction of general anesthesia. The patient had hypertension, diabetes, increased left ventricular wall thickness, and reduced left ventricular fractional shortening. Atrial fibrillation was treated with electrical cardioversion. Atrial fibrillation disappeared and hemodynamic parameters became stable.