TIME-DEPENDENT VARIATIONS OF STIMULUS REQUIREMENTS IN SPINAL-CORD STIMULATION FOR ANGINA-PECTORIS

The aim of the study was to observe changes over time of the stimulati on requirements in spinal cord stimulation (SCS). Of 60 patients treat ed with SCS, 25 patients were selected because they had neurostimulato rs capable of measuring impedance noninvasively, and had not experienc ed electrode displacement. All 25 patients had Medtronic Pisces Quad 3 487A (Medtronic, Inc.) neuroelectrodes with the tip positioned in the thoracic epidural space. The accuracy of the neurostimulators impedanc e measuring circuit was investigated in a test circuit. The error was < 11%. Stimulus requirements and impedance were recorded at the implan tation and at follow-ups during a period of 24 months. During the firs t month after implantation, the stimulus requirements for satisfactory effect varied between +406% and -34%. After that period, only minor d eviations were observed in most patients. To optimize the pain reducin g effect of the spinal cord stimulation, frequent follow-ups are recom mended during the first month; later on, the follow-up intervals can b e extended. No tolerance development or pain resistance developed duri ng SCS treatment.