The lower efficacy of PVI alone in persistent AF has been attributed to adverse electrical, molecular, and structural remodeling of the atria. Collectively, atrial remodeling decreases conduction velocity and the effective refractory period, and results in a shortened atrial wavelength, which increases the number and stability of reentrant wavelets. This can cause persistence of AF independent of a focal discharge. Standard PVI addresses the "focal discharge" or trigger from the PVs that initiates AF but not necessarily the underlying atrial substrate.