Résumé : Idiopathic left ventricular tachycardia is an infrequent form of ventricular tachycardia associated with a structurally normal heart. The prognosis is usually benign; however, sustained cases have been reported. In this report, we describe two cases of persistent idiopathic left ventricular tachycardia complicated by tachycardia-mediated cardiomyopathy. In the first case, the patient developed a right ventricular thrombus with subsequent pulmonary embolism. In the second case, the patient developed acute pulmonary edema. Both cases were cured by catheter ablation.