Tachycardia-induced cardiomyopathy may be provoked by several arrhythmias; it may reverse following stable restoration of sinus rhythm. We report the case of a 33-year-old man who was diagnosed to have a dilated cardiomyopathy. Over a few months, the cardiomyopathy reversed. Subsequently, atrial tachycardia, associated with a recurrent impairment of left ventricular function, occurred. Adenosine infusion during atrial tachycardia caused transient atrioventricular block without the interruption of arrhythmia, which is consistent with a micro-reentrant mechanism. Electroanatomic mapping during tachycardia showed a focus arising from the left superior pulmonary vein ostium. After successful catheter ablation of the focus, left ventricular function fully recovered.