Immediate effects of LL-VNS. The administration of LL-VNS (without affecting sinus rate) immediately suppressed SGNA for approximately 10 sec (from point a to b) before sporadic SGNA reappeared. Upward dashed arrows point to SGNA. Except for the first 5 sec during programmer transmission, chronic LL-VNS did not produce any stimulus artifacts. ECG, electrocardiogram; SGNA, stellate ganglion nerve activity; VNA, vagal nerve activity; SLGPNA, superior left ganglionated plexi nerve activity.