Effect of spinal cord stimulation on heart rate variability and myocardial ischemia in patients with chronic intractable angina pectoris - A prospective ambulatory electrocardiographic study

Background and hypothesis: Spinal cord stimulation is an effective treatment for chronic refractory angina pectoris. Its efficacy is related to an anti-ischemic action, possibly as a result of modulation of the autonomic nervous system. Therefore, the influence of spinal cord stimulation on the autonomic nervous system and myocardial ischemia was prospectively studied in 19 consecutive patients with intractable angina pectoris. Methods: Patients were included when demonstrating > 0.1 mV STsegment depression on the exercise electrocardiogram (EGG) during two separate treadmill tests. After enrollment, heart rate variability together with ischemic indices were studied with 48 h ambulatory ECG monitoring. Assessments were made at baseline and after 6 weeks of spinal cord stimulation therapy. Results: After 6 weeks, no significant changes in heart rate variability were detected. However, ischemic indices on the ambulatory EGG, as well as anginal attacks and consumption of sublingual nitrate tablets, were significantly decreased. Conclusion: Autonomic modulation assessable with heart rate variability analysis may not be the explanatory mechanism of action for the decrease of anginal attacks and ischemia, exerted by spinal cord stimulation used as an adjuvant therapy in patients with chronic intractable angina pectoris.