A remote monitoring system(RMS)has been recommended as a standard management method for patients with cardiac implantable electronic devices, since it enables early detection and therapeutic intervention in arrhythmic events. We experienced three cases with sustained ventricular tachycardia(Sustained VT)with a tachycardia cycle length near the ventricular tachycardia zone(VTZ) , which was misdiagnosed as nonsustained ventricular tachycardia(NSVT)without anti-tachycardia pacing therapy. Evaluation of device electrocardiogram records led us to a definite diagnosis of sustained VTs and early intervention by device reprogramming. The diagnostic algorithms of device programs for NSVT have some limitations that can lead to misdiagnosis, in cases with a VT cycle length near a VT therapy zone. The knowledge of these limitations is necessary to make the most of the advantages of RMS in the early detection and therapeutic intervention in VTs.