Effects of spinal cord stimulation in angina pectoris induced by pacing and possible mechanisms of action

Neuroaugmentation in the management of sacroiliac joint pain. Report of two cases

STUDY DESIGN

A report of two cases of severe sacroiliac pain that were resistant to conventional management techniques. Both patients had undergone lumbar fusion. This appeared to be a predisposing factor.

OBJECTIVE

To define the source of pain in these patients by performing a series of diagnostic blocks under fluoroscopic guidance to determine if these patients were candidates for neuroaugmentation.

SUMMARY OF BACKGROUND DATA

Mild to moderate sacroiliac joint pain can be managed conservatively with analgesics, anti-inflammatory drugs, and physical therapy. Severe sacroiliac joint pain can be incapacitating and more challenging to manage. Fluoroscopically guided intra-articular local anesthetic-steroid injections, followed by joint manipulation, can be effective, intracapsular injections of glycerin, glucose, and phenol also may be beneficial in some patients. The use of neuroaugmentation to manage pain of synovial origin has not been reported previously. Sacral nerve root stimulation in particular has been used to manage urinary bladder dysfunction and pain, but not sacroiliac joint pain.

METHODS

Two patients with severe sacroiliac joint pain were treated by implanting a neuroprosthesis at the third sacral nerve roots. The patients had undergone lumbar fusion for back pain that developed as a result of work-related injuries. Stimulation was tried for 1 week with bilateral, percutaneously implanted, cardiac pacing wires at the third sacral nerve roots.

RESULTS

Both patients experienced relief of approximately 60% of their pain during the trial period. Therefore, a neuroprosthesis (Medtronics, MN) was implanted permanently bilaterally at the third sacral nerve root in both patients. The use of analgesics was reportedly the same after implantation, but significantly more effective, and the patients' daily living activities were more tolerable.

CONCLUSIONS

Two cases of refractory sacroiliac joint pain are reported that were managed with permanently implanted neuroprostheses at the third sacral nerve roots. The authors suggest that neuroaugmentation can be a reasonable option in selected patients with refractory sacroiliac pain.

Electrical stimulation versus coronary artery bypass surgery in severe angina pectoris: the ESBY study

BACKGROUND

Spinal cord stimulation (SCS) has been shown to have antianginal and anti-ischemic effects in severe angina pectoris. The present study was performed to investigate whether SCS can be used as an alternative to coronary artery bypass grafting (CABG) in selected patient groups, ie, patients with no proven prognostic benefit from CABG and with an increased surgical risk.

METHODS AND RESULTS

One hundred four patients were randomized (SCS, 53; CABG, 51). The patients were assessed with respect to symptoms, exercise capacity, ischemic ECG changes during exercise, rate-pressure product, mortality, and cardiovascular morbidity before and 6 months after the operation. Both groups had adequate symptom relief (P<.0001), and there was no difference between SCS and CABG. The CABG group had an increase in exercise capacity (P=.02), less ST-segment depression on maximum (P=.005) and comparable (P=.0009) workloads, and an increase in the rate-pressure product both at maximum (P=.0003) and comparable (P=.03) workloads compared with the SCS group. Eight deaths occurred during the follow-up period, 7 in the CABG group and 1 in the SCS group. On an intention-to-treat basis, the mortality rate was lower in the SCS group (P=.02). Cerebrovascular morbidity was also lower in the SCS group (P=.03).

CONCLUSIONS

CABG and SCS appear to be equivalent methods in terms of symptom relief in this group of patients. Effects on ischemia, morbidity, and mortality should be considered in the choice of treatment method. Taking all factors into account, it seems reasonable to conclude that SCS may be a therapeutic alternative for patients with an increased risk of surgical complications.

Refractory angina pectoris in end-stage coronary artery disease: evolving therapeutic concepts

Refractory angina pectoris in coronary artery disease is defined as the persistence of severe anginal symptoms despite maximal conventional antianginal combination therapy. Further, the option to use an invasive revascularization procedure such as percutaneous coronary balloon angioplasty or aortocoronary bypass grafting must be excluded on the basis of a recent coronary angiogram. This coronary syndrome, which represents end-stage coronary artery disease, is characterized by severe coronary insufficiency but only moderately impaired left ventricular function. Almost all patients demonstrated severe coronary triple-vessel disease with diffuse coronary atherosclerosis, had had one or more myocardial infarctions, and had undergone aortocoronary bypass grafting (70% of cases). We present three new approaches with antiischemic properties: long-term intermittent urokinase therapy, transcutaneous and spinal cord electrical nerve stimulation, and transmyocardial laser revascularization.

Stimulation of the central and peripheral nervous system for the control of pain

After suffering some setbacks since its introduction in 1967, stimulation of the spinal and peripheral nervous systems has undergone rapid development in the last ten years. Based on principles enunciated in the Gate Control Hypothesis that was published in 1968, stimulation-produced analgesia [SPA] has been subjected to intensive laboratory and clinical investigation. Historically, most new clinical ideas in medicine have tended to follow a three-tiered course. Initial enthusiasm gives way to a reappraisal of the treatment or modality as side-effects or unanticipated problems arise. The last and third phase proceeds at a more measured pace as the treatment is refined by experience. This review is divided into three parts as it traces the progress of spinal cord stimulation [SCS] and peripheral nerve stimulation [PNS]. The review commences with a discussion of the theory of SCS and PNS, and is followed by early reports during which it became apparent that the modality is essentially only effective in the treatment of neuropathic pain. The last section describes the modern experience including efficacy in specific types of pain and concludes with recent accomplishments that dramatize the relief of pain which can be achieved in nonoperable peripheral vascular disease or myocardial ischemia. Over the years, a search for those transmitters that might be influenced by spinal cord stimulation focused on somatostatin, cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), neurotensin and other amines, although only substance "P" was implicated. More recently, in animal studies, evidence that GABA-ergic systems are affected may explain the frequent successful suppression of allodynia that follows spinal cord stimulation. During the past eight years, much attention has been directed to studies that use a chronic neuropathic pain model. While PNS held significant promise as a pain relieving modality, early electrode systems and their surgical implantation yielded variable results due to evolving technical and surgical skills. These results dramatically reduced the continued development of PNS, which then gave way to a preoccupation with SCS. Modern development of SCS with outcome studies, particularly in relation to failed back surgery syndrome [FBSS] and the outcome of peripheral nerve surgery for chronic regional pain syndromes, has earned both modalities a place in the ongoing management of patients with intractable neuropathic pain. The last section, dealing with pain of peripheral vascular and myocardial ischemia, is perhaps one of the more exciting developments in stimulation produced analgesia and as the papers discussed demonstrate, can provide a level of analgesia and efficacy that is unattainable by other treatment modalities. SCS and PNS has an important role to play in the management of conditions that are otherwise refractory to conservative or other conventional management.

Angina pectoris refractory for conventional therapy--is neurostimulation a possible alternative treatment?

The treatment of angina pectoris as a symptom of coronary artery disease usually is focused on restoring the balance between oxygen demand and supply of the myocardium by administration of drugs interfering in heart rate, cardiac pre- and afterload, and coronary vascular tone. For nonresponders to drug therapy or for those with jeopardized myocardium, revascularization procedures such as coronary bypass surgery and percutaneous transluminal coronary angioplasty are at hand. However, the atherosclerotic process is not stopped by these therapies and, at longer terms, angina may recur. It is not always possible to revascularize all the patients who do not positively react to medical treatment. Those with angina, not responding to adequate medication and who are not suitable anymore for revascularization, are considered to suffer from refractory angina pectoris. This group of patients has a poor quality of life, for their exercise tolerance is severely afflicted. For these patients, neurostimulation has been described repeatedly as an effective and safe therapy. The mechanism of action of neurostimulation is not completely known, but recent studies suggest an anti-ischemic effect, exerted through changes in myocardial blood flow. As soon as its safety is sufficiently established, it may become a useful alternative in the treatment of refractory angina pectoris.

The effect of transcutaneous electrical nerve stimulation (TENS) on autonomic cardiovascular reflexes

Transcutaneous electrical nerve stimulation (TENS) has been shown to have an anti-ischaemic effect in patients with angina and peripheral vascular disease that appears to be additional to any analgesic action. The mechanism for this anti-ischaemic effect is not known but it is possible that TENS interferes with the autonomic responses to ischaemia. To determine if TENS has any direct action on autonomic reflexes we have assessed the effect of high frequency TENS on a variety of standard tests of autonomic cardiovascular reflexes in 10 normal subjects. Tests were done on four consecutive days at the same time and TENS therapy or placebo was randomly allocated on 2 days each. Results of the tests were assessed by one person 'blinded' to the randomization order. These showed that TENS was associated with a significant reduction in the rise of the diastolic blood pressure (21.8 +/- 2.3 v. 17.6 +/- 17 mmHg; p < 0.05) during isometric exercise, using sustained Handgrip. There was no significant effect discernible on the changes of heart rate and blood pressure during the Valsalva manoeuvre, cold face stimulus or head-up tilt. Transcutaneous electrical nerve stimulation appears, therefore, to have a mild inhibitory action on those reflexes mediated predominantly by the sympathetic nervous system and this is more apparent when the stimulation may be greater, as during isometric exercise.

Efficacy of spinal cord stimulation as adjuvant therapy for intractable angina pectoris: a prospective, randomized clinical study. Working Group on Neurocardiology

OBJECTIVES

In a prospective, randomized study with an 8-week follow-up period, we evaluated the efficacy of spinal cord stimulation on exercise capacity and quality of life in patients with intractable angina.

BACKGROUND

Despite important achievements in therapy for ischemic heart disease, there remain patients with intractable symptoms of angina. In uncontrolled observations, several investigators have reported beneficial effects of spinal cord stimulation as an additional therapy for patients with angina pectoris.

METHODS

Seventeen patients were randomly assigned to the treatment (implantation within 2 weeks, eight patients) or control (implantation after 8 weeks, nine patients) group. Assessment of exercise capacity was performed by treadmill exercise testing. Quality of life was evaluated by daily and social activity scores and recording sublingual glyceryl trinitrate intake and angina pectoris attacks in a diary. After the 8-week study period, the control group also received the spinal cord stimulation device, and all patients were followed up for 12 months.

RESULTS

The treatment but not the control group demonstrated a significant increase in exercise duration (p < 0.02), rate-pressure product (p < 0.03) and time to angina (p < 0.04), with a decrease in ST segment depression (p < 0.05). This was associated with an increase in daily life (p < 0.008) and social activity (p < 0.005) scores and a reduction in glyceryl trinitrate intake (p < 0.004) and episodes of angina pectoris (p < 0.003). During the 1-year follow-up, improvement in all quality of life variables was linear for the entire group compared with baseline. The time to angina, exercise duration and ST segment depression showed a second-order trend.

CONCLUSIONS

Spinal cord stimulation significantly improves exercise capacity and quality of life. On the basis of an increase in exercise capacity and rate-pressure product, the mechanism by which spinal cord stimulation acts may be related to improved oxygen supply to the heart combined with an analgesic effect.

A comparative study of the effect of high-intensity transcutaneous nerve stimulation and oral naproxen on intrauterine pressure and menstrual pain in patients with primary dysmenorrhea

OBJECTIVE

Our purpose was to compare the effects of high-intensity transcutaneous electrical nerve stimulation and oral naproxen (500 mg) on intrauterine pressure and menstrual pain.

STUDY DESIGN

An open, randomized crossover study was performed on 12 women with primary dysmenorrhea. Intrauterine pressure was recorded with a microtransducer catheter, and the pain score was assessed by a visual analog scale.

RESULTS

Before treatment all patients displayed signs of uterine hyperactivity as judged by a high resting pressure (7.5 +/- 0.4 kPa), high active pressure (24.0 +/- 0.8 kPa), and a high frequency of pressure cycles (13.3 +/- 0.5 contractions per 0.5 hour). Oral administration of naproxen suppressed (p < 0.01) all uterine activity parameters. Treatment with transcutaneous electrical nerve stimulation induced a prompt onset of pain relief in a strictly segmental manner, but there were no significant changes in uterine activity. The pain score was significantly reduced (p < 0.001) from 30 to 60 minutes after treatment with transcutaneous electrical nerve stimulation and from 19 to 120 minutes after naproxen administration.

CONCLUSIONS

Treatment with transcutaneous electrical nerve stimulation induced a prompt onset of pain relief without any significant changes in uterine activity. Possible mechanisms for the pain relief, decreased uterine ischemia or decreased activity in the pain transmission system at spinal or supraspinal levels, are discussed.