© 2000 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Modulation of intrinsic cardiac neurons by spinal cord stimulation: implications for its therapeutic use in angina pectoris
aDepartment of Physiology, OUHSC, Oklahoma City, OK 73190, USA
bDepartment of Neurosurgery, Karolinska Institute, Stockholm, Sweden
cDepartment of Pharmacology, University of East Tennessee State University, Johnson City, TN 37614, USA
dCardiology Department and Department of Biological Psychiatry, University and University Hospital of Groningen, Groningen, The Netherlands
eDalhousie University, Faculty of Medicine, Department of Physiology and Biophysics, Sir Charles Tupper Building, Rm 3B-1, 5859 University Avenue, Halifax, Nova Scotia, Canada B3H 4H7
* Corresponding author. Tel.: +1-902-494-3382; fax: +1-902-494-1685 jarmour{at}is.dal.ca
Objective: Electrical stimulation of the dorsal aspect of the upper thoracic spinal cord is used increasingly to treat patients with severe angina pectoris refractory to conventional therapeutic strategies. Clinical studies show that spinal cord stimulation (SCS) is a safe adjunct therapy for cardiac patients, producing anti-anginal as well as anti-ischemic effects. However, little information is yet available about the underlying mechanisms involved. Methods: In order to determine its mechanism of action, the effects of SCS on the final common integrator of cardiac function, the intrinsic cardiac nervous system, was studied during basal states as well as during transient (2 min) myocardial ischemia. Activity generated by intrinsic cardiac neurons was recorded in 9 anesthetized dogs in the absence and presence of myocardial ischemia before, during and after stimulating the dorsal T1–T2 segments of the spinal cord at 66 and 90% of motor threshold using epidural bipolar electrodes (50 Hz; 0.2 ms; parameters within the therapeutic range used in humans). Results: The SCS suppressed activity generated by intrinsic cardiac neurons. No concomitant change in monitored cardiovascular indices was detected. Neuronal activity increased during transient ventricular ischemia (46%), as well as during the early reperfusion period (68% compared to control). Despite that, activity was suppressed during both states by SCS. Conclusions: SCS modifies the capacity of intrinsic cardiac neurons to generate activity. SCS also acts to suppress the excitatory effects that local myocardial ischemia exerts on such neurons. Since no significant changes in monitored cardiovascular indices were observed during SCS, it is concluded that modulation of the intrinsic cardiac nervous system might contribute to the therapeutic effects of SCS in patients with angina pectoris.
KEYWORDS Autonomic nervous system; Ischemia; Reperfusion