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Dear Dr. Groves, Dr. Chester, and Editor,
Thank you for the positive response to our paper on spinal cord stimulation for treatment of patients with refractory angina pectoris.(1)
At the time when we performed the study and wrote the report, we were not aware of your scientific letter dealing with heart rate variability and spinal cord stimulation.(2) Otherwise we would certainly have discussed it in our paper....
At the time when we performed the study and wrote the report, we were not aware of your scientific letter dealing with heart rate variability and spinal cord stimulation.(2) Otherwise we would certainly have discussed it in our paper.
Your study supports our findings in showing that “LF spectral components were significantly diminished in the absence of perceived paraesthesia with SCS.” We are pleased to learn that there is additional data supporting the hypothesis that spinal cord stimulation, even at a level below the sensory threshold, elicits positive effects in patients with refractory angina pectoris.
Heinz Theres, MD
Stephan Eddicks, MD
1. Eddicks S, Maier-Hauff K, Schenk M et al.Thoracic spinal cord stimulation improves functional status and relieves symptoms in patients with refractory angina pectoris: the first placebo-controlled randomised study.Heart. 2007;93:585-590.
2. Moore R, Groves D, Nolan J et al. Altered short term heart rate variability with spinal cord stimulation in chronic refractory angina: evidence for the presence of procedure related cardiac sympathetic blockade.Heart. 2004;90:211-212.
Eddicks and colleagues’ placebo controlled study of spinal cord stimulation in refractory angina is important and interesting work which shows for the first time that patient appreciation of the sensation of spinal cord stimulation is not necessary to achieve clinical benefit.
The article gives the impression that no previous work had been carried out investigating sub-sensory threshold Spinal...
The article gives the impression that no previous work had been carried out investigating sub-sensory threshold Spinal Cord Stimulation (SCS) applied clinically to refractory angina patients and that, before their work, the
possibility of therapeutic effect of SCS applied at sub-sensory threshold levels could only be deduced from animal studies. This requires clarification.
In 2004, we published the findings of a study in Heart in which we evaluated the effect of full therapeutic, half therapeutic (sub sensory threshold) and zero (placebo) voltages of spinal cord stimulation in refractory angina
patients who, like the patients in Eddicks’ study, had all benefited from spinal cord stimulation (1).
Our study showed that full (sensory) therapeutic voltage and half (sub-sensory) therapeutic voltage SCS both brought about a significant reduction in cardiac sympathetic drive (as measured by low frequency heart rate variability) compared to that brought about by zero(placebo) voltage SCS.
From this we deduced that analgesia in refractory angina patients is brought about at least in part by SCS producing cardiac sympathetic blockade. We postulated that, “prolonged stimulation at this lower level could offer lessening in the total ischaemic burden and possibly altered arrhythmia thresholds for this patient group.”
1. Altered short term heart rate variability with spinal cord stimulation in chronic refractory angina: evidence for the presence of procedure related cardiac sympathetic blockade. R Moore, D Groves, J Nolan, D Scutt, J Pumprla, MR ChesterHeart 2004;90:211-212