This chapter focuses on the assessment and nonpharmacologic treatment of verapamil-sensitive left fascicular ventricular tachycardia (VT). Verapamil-sensitive left fascicular VT (reentry), VT with a focal origin in the distal Purkinje system (abnormal automaticity), left ventricular outflow tract VT and VT from the mitral annulus are the four types of idiopathic left VT. Idiopathic VTs usually occur in specific locations and have specific QRS morphologies, whereas VTs associated with structural heart disease have a QRS morphology that tends to indicate the location of the scar. Idiopathic VT comprises multiple discrete subtypes that are best differentiated by their mechanism, QRS morphology, and site of origin. The most common idiopathic VT originates from a focus in the outflow tract of the right ventricle, and its mechanism is most likely triggered activity. A detailed discussion on the classification and pathophysiology of idiopathic left VT, diagnostic criteria of idiopathic left VT, and mapping and ablation has been provided in this chapter.