STIMULATION CHARACTERISTICS, COMPLICATIONS, AND EFFICACY OF SPINAL-CORD STIMULATION SYSTEMS IN PATIENTS WITH REFRACTORY ANGINA - A PROSPECTIVE FEASIBILITY STUDY

Objectives: In a prospective study with a 1-year follow-up we evaluate d: (1) the feasibility of a method for the adjustment of spinal cord s timulator (SCS) parameters, (2) complications of SCS, and (3) efficacy of SCS. Methods: In patients receiving an SCS for severe angina unres ponsive to standard therapies, SCS characteristics were evaluated with in 1 week and at 4, 14, 26, and 52 weeks after SCS treatment. Step-by- step adjustment of pulse output parameters was performed at the electr ode configuration at which paresthesias occurred (''sensory threshold' '), covered the anginal area (''adjusted setting''), or provoked pain (''motor threshold''). In addition, the number of anginal attacks and intake of glyceryl trinitrate (GTN) tablets were recorded at regular i ntervals. Results: Twenty-two patients with either a bipolar (14) or a unipolar (8) system were evaluated. In the 14 patients with bipolar s ystems, alteration in paresthesias required 26 reprogrammings of the c onfiguration. in the eight patients with bipolar systems who completed the followup without lead dislocation, the mean ''sensory threshold'' was 3.3 V (1.7-5.6), the mean ''adjusted stimulation'' output was 4.5 V (2.8-7.6), and the mean ''motor threshold'' was 4.9 V (2.8-7.7) aft er 4 weeks SCS. The mean stimulation duration per 24 hours was 14.2% ( 5%-24%), and the mean standardized impedance was 821 Omega (748-893) a fter 4 weeks SCS. The unipolar group demonstrated comparable results. After 1-year follow-up the parameters had not changed significantly. D uring the I-year followup, 6 of 22 patients experienced lead dislocati on that required surgery. In all patients, anginal attacks (P < 0.003) and GTN intake (P < 0.005) were reduced significantly with SCS. The e ffect lasted during the 1 year. Conclusions: During a 1-year follow-up , the stimulation parameters did not change significantly in the 16 pa tients without lead dislocations. Our standardized method appears to b e feasible for followup of SCS. Moreover, SCS seems to be an effective adjuvant therapy for intractable angina, despite a relatively frequen t dislocation of the electrode.