A 17-year-old woman was found to have ectopic atrial tachycardia by her physician. Echocardiography and cardiac catheterization revealed findings resembling dilated cardiomyopathy at the time of initial presentation. The tachycardia was controlled with atenolol only at a dose of 50 mg/day. However, at the age of 22, the presence of ectopic atrial tachycardia was once again confirmed. We successfully performed catheter ablation for persistent ectopic atrial tachycardia. Serial echocardiographic findings showed the left ventricular dimension and function appeared to return to normal 1 year postablation. However, despite pharmacologic control and catheter ablation therapy, histopathology revealed myocardial fibrosis presumably representing permanent damage of the heart secondary to tachycardia 1 year postablation.