Spinal electrical stimulation for intractable angina--long-term clinical outcome and safety

Cardiovascular Effects of Spinal Cord Stimulation: The Highs, the Lows, and the Don't Knows

BACKGROUND AND OBJECTIVES

There are many potential etiologies of impaired cardiovascular control, from chronic stress to neurodegenerative conditions or central nervous system lesions. Since 1959, spinal cord stimulation (SCS) has been reported to modulate blood pressure (BP), heart rate (HR), and HR variability (HRV), yet the specific stimulation sites and parameters to induce a targeted cardiovascular (CV) change for mitigating abnormal hemodynamics remain unclear. To investigate the ability and parameters of SCS to modulate the CV, we reviewed clinical studies using SCS with reported HR, BP, or HRV findings.

MATERIALS AND METHODS

A keyword-based electronic search was conducted through MEDLINE, Embase, and PubMed data bases, last searched on February 3, 2023. Inclusion criteria were studies with human participants receiving SCS with comparison with SCS turned off, with reporting of either HR, HRV, or BP findings. Non-English studies, conference abstracts, and studies not reporting standalone effects of SCS when comparing SCS with non-SCS interventions were excluded. Results were plotted for visual analysis. When available, participant-specific stimulation parameters and effects were extracted and quantitatively analyzed using ordinary least squares regression.

RESULTS

A total of 59 studies were included in this review; 51 studies delivered SCS invasively through implanted/percutaneous leads. Eight studies used noninvasive, transcutaneous electrodes. We found numerous reports of cervical, high thoracic, and mid-to-low thoracolumbar SCS increasing resting BP, and cervical/mid-to-low thoracolumbar SCS decreasing BP. The effect of SCS location on HR and HRV was equivocal. We were unable to analyze stimulation parameters owing to inadequate parameter reporting in many publications.

CONCLUSIONS

Our findings suggest CV neuromodulation, particularly BP modulation, with SCS to be a promising frontier. Further research with larger randomized controlled trials and detailed reporting of SCS parameters will be necessary for appropriate evaluation of SCS as a CV therapy.

Incidence of Lead Migration With Loss of Efficacy or Paresthesia Coverage After Spinal Cord Stimulator Implantation: Systematic Review and Proportional Meta-Analysis of Prospective Studies and Randomized Clinical Trials

OBJECTIVE

The objective of this meta-analysis was to approximate the incidence of overall lead migration, clinically significant lead migration, and asymptomatic lead migration in patients who have undergone spinal cord stimulator implantation.

MATERIALS AND METHODS

A comprehensive literature search was performed for studies published before May 31, 2022. Only randomized controlled trials and prospective observational studies with more than ten patients were included. Two reviewers analyzed the articles from the literature search for final inclusion, after which, study characteristics and outcome data were extracted. The primary dichotomous categorical outcome variables were the incidence of overall lead migration, clinically significant lead migration (defined as lead migration resulting in loss of efficacy), and asymptomatic lead migration (defined as lead migration discovered incidentally on follow-up imaging) in patients with spinal cord stimulator implant. Freeman-Tukey arcsine square root transformation for meta-analysis of proportions using random effects (DerSimonian and Laird method) was used to calculate incidence rates for the outcome variables. Pooled incidence rates and 95% CIs were calculated for the outcome variables.

RESULTS

Fifty-three studies met the inclusion criteria, with a total of 2932 patients having received spinal cord stimulator implants. The pooled incidence of overall lead migration was 9.97% (95% CI of 7.62%-12.59%). Only 24 of the included studies commented on the clinical significance of reported lead migrations, of which every lead migration was clinically significant. In these 24 studies, 96% of the reported lead migrations required a revision procedure or explant. Unfortunately, no studies that reported lead migration commented on asymptomatic lead migrations; therefore, the incidence of asymptomatic lead migrations could not be defined.

CONCLUSIONS

This meta-analysis found that the rate of lead migration in patients who have received spinal cord stimulator implants is approximately one in ten patients. This likely closely approximates the incidence of clinically significant lead migration owing to the included studies not routinely performing follow-up imaging. Therefore, lead migrations were primarily discovered owing to loss of efficacy, and no included studies clearly reported asymptomatic lead migration. The results of this meta-analysis can be used to inform patients more accurately on the risks and benefits of spinal cord stimulator implantation.

Neuromodulation in patients with refractory angina pectoris: a review

The number of patients with coronary artery disease (CAD) who have persisting angina pectoris despite optimal medical treatment known as refractory angina pectoris (RAP) is growing. Current estimates indicate that 5-10% of patients with stable CAD have RAP. In absolute numbers, there are 50 000-100 000 new cases of RAP each year in the USA and 30 000-50 000 new cases each year in Europe. The term RAP was formulated in 2002. RAP is defined as a chronic disease (more than 3 months) characterized by diffuse CAD in the presence of proven ischaemia which is not amendable to a combination of medical therapy, angioplasty, or coronary bypass surgery. There are currently few treatment options for patients with RAP. One such last-resort treatment option is spinal cord stimulation (SCS) with a Class of recommendation IIB, level of evidence B in the 2019 European Society of Cardiology guidelines for the diagnosis and management of chronic coronary syndromes. The aim of this review is to give an overview of neuromodulation as treatment modality for patients with RAP. A comprehensive overview is given on the history, proposed mechanism of action, safety, efficacy, and current use of SCS.

Management of refractory angina: an update

Despite the use of anti-anginal drugs and/or percutaneous coronary interventions (PCI) or coronary artery bypass grafting, the proportion of patients with coronary artery disease who have daily or weekly angina ranges from 2% to 24%. Refractory angina refers to long-lasting symptoms (for >3 months) due to established reversible ischaemia, which cannot be controlled by escalating medical therapy with the use of 2nd- and 3rd-line pharmacological agents, bypass grafting, or stenting. While there is uncertain prognostic benefit, the treatment of refractory angina is important to improve the quality of life of the patients affected. This review focuses on conventional pharmacological approaches to treating refractory angina, including guideline directed drug combination and dosages. The symptomatic and prognostic impact of advanced and novel revascularization strategies such as chronic total occlusion PCI, transmyocardial laser revascularization, coronary sinus occlusion, radiation therapy for recurrent restenosis, and spinal cord stimulation are also covered and recommendations of the 2019 ESC Guidelines on the Diagnosis and Management of Chronic Coronary Syndromes discussed. Finally, the potential clinical use of current angiogenetic and stem cell therapies in reducing ischaemia and/or pain is evaluated.

An evidence-based review of neuromodulation for the treatment and management of refractory angina

Angina pectoris is defined as substernal chest pain that is typically exacerbated by exertion, stress, or other exposures. There are various methods of treatment for angina. Lifestyle modification and pharmacological management are considered as conservative treatments. If these medications do not result in the resolution of pain, more invasive approaches are an option, like coronary revascularization. Refractory angina (RA) is differentiated from acute or chronic angina based on the persistence of symptoms despite conventional therapies. Overall, the prevalence of RA is estimated to be 5%-15% in patients with coronary artery disease, which can account for up to 1,500,000 current cases and 100,000 new cases in the United States per year. Spinal cord stimulation treatment is a viable option for patients who are suffering from RA pain and are either not candidates for revascularization surgery or are currently not being well managed on more traditional treatments. Many studies show a positive result.

The sympathetic innervation of the heart: Important new insights

Autonomic control of the heart has a significant influence over development of life threatening arrhythmias that can lead to sudden cardiac death. Sympathetic activity is known to be upregulated during these conditions and hence the sympathetic nerves present a target for treatment. However, a better understanding of the anatomy and physiology of cardiac sympathetic nerves is required for the progression of clinical interventions. This review explores the organization of the cardiac sympathetic nerves, from the preganglionic origin to the postganglionic innervations, and provides an overview of literature surrounding anti-arrhythmic therapies including thoracic sympathectomy and dorsal spinal cord stimulation. Several features of the innervation are clear. The cardiac nerves differentially supply the nodal and myocardial tissue of the heart and are dependent on activity generated in spinal neurones in the upper thoracic cord which project to synapse with ganglion cells in the stellate complex on each side. Networks of spinal interneurones determine the pattern of activity. Groups of spinal neurones selectively target specific regions of the heart but whether they exhibit a functional selectivity has still to be elucidated. Electrical or ischemic signals can lead to remodeling of nerves in the heart or ganglia. Surgical and electrical methods are proving to be clinically beneficial in reducing atrial and ventricular arrhythmias, heart failure and severe cardiac pain. This is a rapidly developing area and we need more basic understanding of how these methods work to ensure safety and reduction of side effects.

Treatment of Inoperable Coronary Disease and Refractory Angina: Spinal Stimulators, Epidurals, Gene Therapy, Transmyocardial Laser, and Counterpulsation

Intractable angina from refractory coronary disease is a severe form of myocardial ischemia for which revascularization provides no prognostic benefit. Inoperable coronary disease is also accompanied by a “vicious cycle” of myocardial dystrophy from a chronic alteration of the cardiac sympathetic tone and sensitization of damaged cardiac tissues. Several adjunctive treatments have demonstrated efficacy when revascularization is either unsuccessful or contraindicated. Spinal cord stimulation modifies the neurologic input and output of the heart by delivering a very low dose of electrical current to the dorsal columns of the high thoracic spinal cord. Neural fibers then release CGRP and other endogenous peptides to the coronary circulation reducing myocardial oxygen demand and enhancing vasodilation of collaterals to improve the myocardial blood flow of the most diseased regions of the heart. Randomized study has shown the survival data at five years is comparable to bypass for high-risk patients. Transmyocardial laser revascularization creates small channels into ischemic myocardium in an effort to enhance flow though studies have shown no improvement in prognosis over medical therapy alone. Enhanced external counterpulsation uses noninvasive pneumatic compression of the legs to improve diastolic filling of the coronary vessels and promote development of collateral flow. The compressor regimen requires thirty-five hours of therapy over a seven-week treatment period. Therapeutic angiogenesis requires injection of cytokines to promote neovascularization and improve myocardial perfusion into the regions affected by chronic ischemia. Phase 3 trials are pending. High thoracic epidural blockade produces a rapid and potent sympatholysis, coronary vasodilation and reduced myocardial oxygen demand in refractory coronary disease. This technique can be used as an adjunct to bypass surgery or medical therapy in chronic or acute unstable angina. Epidurals are easy to perform and often available for outpatient or inpatient use. The rapid anti-ischemic effect may complement therapeutic angiogenesis or other interventions with delayed onset to clinical benefit. A new era for interventional and implant cardiology is beginning to emerge as more clinicians, including cardiologists, gradually learn new procedures to safely provide more therapeutic options for patients suffering refractory angina.

Spinal cord stimulation is safe and feasible in patients with advanced heart failure: early clinical experience

AIMS

Pre-clinical work suggests that upper thoracic spinal cord stimulation (SCS) may have therapeutic effects in the treatment of heart failure (HF). We therefore aim to assess the safety and feasibility of SCS in HF patients.

METHODS AND RESULTS

A prospective, randomized, double-blind, crossover pilot study was conducted in symptomatic HF patients receiving optimal medical therapy. Patients were implanted with an SCS system and randomized to an SCS-ACTIVE, delivered at 90% paraesthesia threshold, or an SCS-INACTIVE phase for 3 months, followed by a 1-month washout period and crossover to the alternative phase. The safety of SCS therapy was assessed by death and cardiac events. Implantable cardioverter defibrillator (ICD) function in the presence of SCS was tested by defibrillation testing during SCS system implant and review of real-time and stored electrograms during follow-up. The efficacy of SCS therapy was assessed by changes in patient symptoms, LV function, and BNP level. Nine patients were investigated. In all cases, ICD sensing, detection, and therapy delivery were unaffected by SCS. During follow-up, one patient died and one was hospitalized for HF while in the SCS-INACTIVE phase, and two patients had HF hospitalizations during the SCS-ACTIVE phase. Symptoms were improved in the majority of patients with SCS, while markers of cardiac structure and function were, in aggregate, unchanged.

CONCLUSION

This study shows that an SCS system can be safely implanted in patients with advanced HF and that the SCS system does not interfere with ICD function.

Interventional treatment of pain in refractory angina. A review

BACKGROUND

Refractory angina is characterized by repeated attacks of chest pain in patients on maximal anti-anginal pharmacotherapy, with a professional conscensus that further surgical or radiological revascularization would be futile. Refractory angina is a serious but relatively uncommon health problem, with a reported incidence of approximately 30 patients per million people/year. In this condition simply treating the associated pain alone is important as this can improve exercise tolerance and quality of life.

METHODS

An extensive literature search using five different medical databases was performed and from this, eighty-three papers were considered appropriate to include within this review.

RESULTS AND CONCLUSION

Available literature highlights several methods of interventional pain treatment, including spinal cord stimulation and video-assisted upper thoracic sympathectomy which can provide good analgesia whilst improving physical activities and quality of life. The positive effect of spinal cord stimulation on the intensity of pain and quality of life has been confirmed in nine randomized controlled trials. Other potential treatment methods include stellate ganglion blocks, insertion of thoracic epidural or spinal catheters and transcutaneous electrical nerve stimulation. These approaches however appear more useful for diagnostic purposes and perhaps as short-term treatment measures.

Spinal Cord Stimulation and the Induction of c-fos and Heat Shock Protein 72 in the Central Nervous System of Rats

For more than a decade, spinal cord stimulation (SCS) has been used as an adjuvant treatment for patients who are unresponsive to conventional therapies for angina pectoris. Many studies showed that SCS has both electro-analgesic and anti-ischemic effects. Nonetheless, the biological substrates by which SCS acts have not yet been unraveled, although recently areas in the brain have been described that show changes in blood flow, following SCS, and during provocation of angina. In search of a putative mechanism of action of SCS, we hypothesized that SCS affects processing of nociceptive information within the central nervous system (CNS). Moreover, it may alter the limbic system activity that maintains the balance between sympathetic and parasympathetic activity in the heart. Hence, we have developed a rat model to investigate its suitability for studying the induction of neural activity during SCS. To characterize neural activity, we used the expression of both the immediate early gene c-fos and the heat shock protein 72 (HSP72). c-Fos was used to identify structures in the CNS affected by SCS, and HSP72 was applied in order to ascertain whether SCS might operate as a stressor. In 20 halothane-anesthetized male Wistar rats, two electrodes were placed epidurally, one at the C7 level and the other at the T2 level. Two days after surgery, the rats were either stimulated "treated" animals, n = 10) or used as controls ("unstimulated" = "sham," n = 10) in random order. Furthermore, we studied the effect of SCS on behavior in five treated and five control rats. Three hours after stimulation, the rats were euthanized and the brain and spinal cord were removed. The treated group showed regional increased c-fos expression in regions of the limbic system (periaqueductal gray, paraventricular hypothalamic nucleus, paraventricular thalamic nucleus, central amygdala, agranular and dysgranular insular cortex, (peri)ambiguus, nucleus tractus solitarius, and spinal cord) that are involved in the processing of pain and cardiovascular regulation, among other things. Moreover, in both treated rats and controls, HSP72-expression was found in the endothelium of the enthorhinal cortex, the amygdala, and the ventral hypothalamus, but not in the neurons. Finally, treated animals were significantly more alert and active than controls. In conclusion, the rat model we developed appears to be suitable for studying potential mechanisms through which SCS may act. In addition, SCS affects c-fos expression in specific parts of the brain known to be involved in regulation of pain and emotions. HSP72-expression is limited to the endothelium of certain parts of the CNS and thereby excludes physical stress effects as a potential mechanism of SCS.

Spinal cord stimulation has proven benefit on pain and quality of life in patients with angina pectoris when less invasive therapies have failed

Background.  Since 1988, spinal cord stimulation (SCS) has been used at Odense University Hospital for patients with refractory angina pectoris. The aim of our prospective study was to evaluate the long-term effects of SCS on pain, activities of daily living (ADLs), quality of life (QOL), sleep hygiene, and physical functioning for patients with angina pectoris. Methods.  Before and after placement of SCS for patients with intractable angina pectoris, we performed structured telephone interviews questioning for pain relief, ADLs (Nottingham Health Profile), physical functioning (Seattle Angina Questionnaire) and sleep hygiene. Results.  Out of 150 patients with SCS over 15 years, 41 patients had died, 46 patients had their devices explanted, and four patients did not participate or could not be reached. Three patients had less than 6 months of follow-up and were therefore not included in our analysis. The beneficial effects of SCS treatment for intractable angina pectoris were reduction in pain and improvement in QOL. Sleep pattern and physical functioning were not improved to the same extent as reduction in pain or improvement in QOL. Almost all of our SCS-treated patients did recommend SCS for intractable angina pectoris. About 30% of patients discontinued treatment, the most common cause being electrode displacement and malfunction of the system. Other reasons for discontinued therapy were the evolvement of invasive treatment options such as coronary artery bypass graft and PTCA and use of such options in some patients during our prolonged observation period. Conclusion.  This survey shows that SCS leads to a 70-80% improvement in pain, which, in turn, leads to improvement in QOL, whereas, physical condition and sleep pattern did not improve to the same extent.

Spinal cord stimulation for refractory angina pectoris -a case report-

Refractory angina pectoris is defined as angina refractory to optimal medical treatment and standard coronary revascularization procedures. Despite recent therapeutic advances, patients with refractory angina pectoris are not adequately treated. Spinal cord stimulation is a minimally invasive and reversible technique which utilizes electrical neuromodulation by means of an electrode implanted in the epidural space. It has been reported to be an effective and safe treatment for refractory angina pectoris. We report a case of spinal cord stimulation which has effectively relieved chest pain due to coronary artery disease in a 40-year-old man. This is the first report of spinal cord stimulation for treatment of refractory angina pectoris in South Korea.

Electrical modalities beyond pacing for the treatment of heart failure

In this review, we report on electrical modalities, which do not fit the definition of pacemaker, but increase cardiac performance either by direct application to the heart (e.g., post-extrasystolic potentiation or non-excitatory stimulation) or indirectly through activation of the nervous system (e.g., vagal or sympathetic activation). The physiological background of the possible mechanisms of these electrical modalities and their potential application to treat heart failure are discussed.

24. Chronic refractory angina pectoris

Angina pectoris, cardiac pain associated with ischemia, is considered refractory when optimal anti-anginal therapy fails to resolve symptoms. It is associated with a decreased life expectancy and diminishes the quality of life. Spinal cord stimulation (SCS) may be considered for patients who have also undergone comprehensive interventions, such as coronary artery bypass graft (CABG) and percutaneous transluminal coronary angioplasty (PTCA) procedures. The mechanism of action of SCS is not entirely clear. Pain reduction is related to the increased release of inhibitory neuropeptides as well as normalization of the intrinsic nerve system of the heart muscle, and may have a protective myocardial effect. SCS in patients with refractory angina pectoris results in reduced anginal attacks as well as improved rate pressure product prior to the occurrence of ischemic events. This may be the result of reduced Myocardial Volume Oxygen (MVO(2) ) and possibly the redistribution of the coronary blood flow to ischemic areas. There are a number of studies that demonstrate that SCS does not mask acute myocardial infarction. The efficacy of the treatment has been investigated in two prospective, randomized studies. The long-term results showed an improvement of the symptoms and of the quality of life. SCS can be an alternative to surgical intervention in a selected patient population. In addition, SCS is a viable option in patients in whom surgery is not possible. SCS is recommended in patients with chronic refractory angina pectoris that does not respond to conventional treatment and in whom revascularization procedures have been attempted or not possible, and who are optimized from a medical perspective.

Recent advances in the management of chronic stable angina II. Anti-ischemic therapy, options for refractory angina, risk factor reduction, and revascularization

The objectives in treating angina are relief of pain and prevention of disease progression through risk reduction. Mechanisms, indications, clinical forms, doses, and side effects of the traditional antianginal agents - nitrates, β-blockers, and calcium channel blockers - are reviewed. A number of patients have contraindications or remain unrelieved from anginal discomfort with these drugs. Among newer alternatives, ranolazine, recently approved in the United States, indirectly prevents the intracellular calcium overload involved in cardiac ischemia and is a welcome addition to available treatments. None, however, are disease-modifying agents. Two options for refractory angina, enhanced external counterpulsation and spinal cord stimulation (SCS), are presented in detail. They are both well-studied and are effective means of treating at least some patients with this perplexing form of angina. Traditional modifiable risk factors for coronary artery disease (CAD) - smoking, hypertension, dyslipidemia, diabetes, and obesity - account for most of the population-attributable risk. Individual therapy of high-risk patients differs from population-wide efforts to prevent risk factors from appearing or reducing their severity, in order to lower the national burden of disease. Current American College of Cardiology/American Heart Association guidelines to lower risk in patients with chronic angina are reviewed. The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed that in patients with stable angina, optimal medical therapy alone and percutaneous coronary intervention (PCI) with medical therapy were equal in preventing myocardial infarction and death. The integration of COURAGE results into current practice is discussed. For patients who are unstable, with very high risk, with left main coronary artery lesions, in whom medical therapy fails, and in those with acute coronary syndromes, PCI is indicated. Asymptomatic patients with CAD and those with stable angina may defer intervention without additional risk to see if they will improve on optimum medical therapy. For many patients, coronary artery bypass surgery offers the best opportunity for relieving angina, reducing the need for additional revascularization procedures and improving survival. Optimal medical therapy, percutaneous coronary intervention, and surgery are not competing therapies, but are complementary and form a continuum, each filling an important evidence-based need in modern comprehensive management.

Spinal Cord Stimulation for Chronic Pain

Spinal cord stimulation (SCS) is one of the most effective modalities for management of re- fractory neuropathic pain unresponsive to conservative therapies. The SCS has been successful in providing analgesia, improving function, and enhancing quality of life for patients suffering from chronic pain conditions such as failed back surgery syndrome, complex regional pain syndrome, ischaemic and phantom limb pain, and coronary artery disease. This technique has proven to be cost effective in the long term despite its high initial cost. In this review article, we discuss the history of SCS development, mechanism of action, and indications for SCS. Key words: Failed back surgery syndrome, Ischaemic pain, Neuropathic pain

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 (ECG) 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 ECG, 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.

Spinal Cord Stimulation Improves Ventricular Function and Reduces Ventricular Arrhythmias in a Canine Postinfarction Heart Failure Model

Background— Spinal cord stimulation (SCS) reduces the incidence of ventricular tachyarrhythmias in experimental models. This study investigated the effects of long-term SCS on ventricular function in a postinfarction canine heart failure model.

Methods and Results— In stage 1, dogs underwent implantable cardioverter-defibrillator implantation and embolization of the left anterior descending artery followed by right ventricular pacing (240 ppm) for 3 weeks to produce heart failure. In stage 2, 28 surviving animals were assigned to the SCS (delivered at the T4/T5 spinal region for 2 hours 3 times a day), medicine (MED; carvedilol therapy at 12.5 mg PO BID), or control (CTRL; no therapy) group for the initial phase 1 study. In a subsequent phase 2 study, 32 stage 1 survivors were equally randomized to the SCS, MEDS (carvedilol plus ramipril 2.5 mg PO QD), SCS plus MEDS (concurrent therapy), or CTRL group. Animals were monitored for 5 weeks (phase 1) or 10 weeks (phase 2). In stage 3, all phase 1 animals underwent circumflex artery balloon occlusion for 1 hour. In the SCS group, left ventricular ejection fraction was 65±5% at baseline, 17±3% at the end of stage 1, and 47±7% at the end of stage 2. In the MED group, left ventricular ejection fraction was 61±4% at baseline, 18±3% at the end of stage 1, and 34±4% at the end of stage 2. In the CTRL group, left ventricular ejection fraction was 64±5% at baseline, 19±5% at the end of stage 1, and 28±3% at the end of stage 2. Left ventricular ejection fraction was significantly improved in the SCS compared with the MED and CTRL groups ( P <0.001 for both). The mean number of spontaneous nonsustained ventricular tachyarrhythmias during stage 2 and the occurrence of ischemic ventricular tachyarrhythmias during stage 3 also were significantly decreased in the SCS (27±17 and 27%, respectively; P <0.03) and MED (58±42 and 33%; P <0.05) versus CTRL (88±52 and 76%) group. After 10 weeks in the phase 2 studies, the greatest recovery in ejection fraction was noted in the SCS (52±5%) and SCS+MEDS (46±4%) groups compared with the MEDS (38±2%) and CTRL (31±4%) groups.

Conclusion— SCS significantly improved cardiac contractile function and decreased ventricular arrhythmias in canine heart failure.

Spinal cord stimulation in severe angina pectoris--a systematic review based on the Swedish Council on Technology assessment in health care report on long-standing pain

Patients who continue to suffer from lasting and severely disabling angina pectoris despite optimum drug treatment and who are not suitable candidates for invasive procedures, suffer from a condition referred to as "chronic refractory angina pectoris". Based on the available data, spinal cord stimulation, SCS, is considered as the first-line additional treatment for these patients by the European Society of Cardiology. However, no systematic review of randomised controlled studies has yet been published. A systematic literature research, 1966-2003, as part of the Swedish Board of Health and Welfare (SBU) report on long-standing pain, and an additional research covering the years 2003-2007, were carried out. Acute studies, case reports and mechanistic reviews were excluded, and the remaining 43 studies were graded for study quality according to a modified Jadad score. The eight medium- to high-score studies formed the basis for conclusions regarding the scientific evidence (strong, moderately strong or limited) for the efficacy of SCS. There is strong evidence that SCS gives rise to symptomatic benefits (decrease in anginal attacks) and improved quality of life in patients with severe angina pectoris. There is also a strong evidence that SCS can improve the functional status of these patients, as illustrated by the improved exercise time on treadmill or longer walking distance without angina. In addition, SCS does not seem to have any negative effects on mortality in these patients (limited scientific evidence). The complication rate was found to be acceptable.

Spinal cord stimulation: an update

Spinal cord stimulation has been used in the treatment of many chronic pain disorders since 1967. In this update, the indications for spinal cord stimulation are reviewed with attention to recent publications. A focused review of the literature on abdominal and visceral pain syndromes is also provided. Furthermore, the technology has evolved from the use of monopolar electrodes to complex electrode arrays. Similarly, the power source has changed from a radio frequency-driven system to a rechargeable impulse generator. These topics are covered, along with a short discussion of implant technique. Finally, we include a review of complications of such therapy. SCS as a technology and therapy continues to evolve.

Spinal cord stimulation for refractory chronic angina pectoris: influence on quality of life

Percutaneous coronary revascularization, coronary artery bypass graft surgery and medical management are nowadays very effective in treating coronary artery disease. Nevertheless, the number of patients affected by refractory chronic angina pectoris is increasing. Epidemiological estimates for refractory angina pectoris predict the diagnosis of more than 100,000 patients each year in the USA and approximately 50,000 in Europe. Spinal cord stimulation is a valuable therapeutic option for patients who have failed multiple percutaneous and surgical revascularizations and who are not eligible for further revascularization procedures. The aim of this study is to assess the benefits, in terms of quality of life, of spinal cord stimulation in no-option patients affected by refractory angina pectoris.

A brief cognitive-behavioral intervention reduces hospital admissions in refractory angina patients

Chronic refractory angina is an increasingly prevalent, complex chronic pain condition, which results in frequent hospitalization for chest pain. We have previously shown that a novel outpatient cognitive-behavioral chronic disease management program (CB-CDMP) improves angina status and quality of life in such patients. In the present study of 271 chronic refractory angina patients enrolled in our CB-CDMP, total hospital admissions were reduced from 2.40 admissions per patient per year to 1.78 admissions per patient per year (P<0.001). The rising trend of total hospital bed day occupancy prior to enrollment fell from 15.48 days per patient per year to a stable 10.34 days per patient per year (P<0.001). There were 32 recorded myocardial infarctions prior to enrollment compared to eight in the year following enrollment (14% vs. 2.3%, P<0.001) and overall mortality was lower that comparable groups treated with surgery. This study shows that educating patients and demystifying angina using a brief outpatient CB-CDMP produces an immediate and sustained reduction in hospital admission costs that represents a major potential health care saving. This benefit accrues in addition to the known effects of CB-CDMP on symptoms and quality of life. These data suggest that a CB-CDMP approach to symptom palliation represents a low cost alternative to palliative revascularization.

Neurostimulation for refractory angina pectoris

Spinal cord stimulation (SCS) has been shown to be particularly useful, safe and effective treatment in the management of patients with refractory angina pectoris and those unsuitable for percutaneous or surgical revascularisation. Clinical and experimental research has shown that it decreases myocardial ischemia without masking the clinical symptoms of its imminent development. In addition to providing pain relief, neurostimulation has also been shown to improve microcirculatory blood flow and increase the myocardial threshold for ischaemia. The anti-ischaemic effects of SCS have been evaluated by: (a) exercise testing, (b) ambulatory electrocardiogram (ECG), and (c) invasive measurements of lactate from coronary sinus blood samples. Patients have reported not only significantly fewer angina attacks but also decreased consumption of glyceryl trinitrate and improved quality of life. A number of mechanisms have been proposed including placebo effects, primary anti-nociceptive effects, involvement of endogenous opiates, anti sympathetic nervous system effects, increases in coronary blood flow, and redistribution of myocardial blood flow.

Spinal cord stimulation for refractory angina pectoris: a retrospective analysis of efficacy and cost-benefit

BACKGROUND

Patients with refractory angina pectoris have severe symptoms despite optimal medication, but are not suitable for revascularisation. Spinal cord stimulation (SCS) has been used for treating refractory angina pectoris since 1985. The efficacy of SCS has been proven by randomised controlled trials and follow-up studies have shown that SCS is a safe treatment. The objective of the current study was to retrospectively analyse the clinical outcomes and cost-benefit of SCS in patients with refractory angina pectoris.

METHODS

Eighteen months after SCS implantation, the effects on Canadian Cardiovascular Society (CCS) functional level and acute symptom relief of 24 patients with permanent SCS were analysed by review of medical records. Nineteen of these 24 patients were able to report their anginal frequency, nitroglycerin consumption and subjective perception on physical activity and quality of life.

RESULTS

Angina frequency decreased from a median of 14.0 to 2.3 attacks/week (p < 0.01). Nitroglycerin intake decreased from a median of 27.5 to 1.5 doses/week (p < 0.01). Canadian Cardiovascular Society angina class improved from a median of three to two (p < 0.001). During a three-year period before SCS implantation, the hospitalisation rate and duration related to coronary artery disease increased progressively. The duration of hospitalisation increased from a median of three to 10 days/patient/year. In the year after SCS implantation the duration of hospitalisation decreased to a median of 0 day/patient/year (p < 0.001). The cost of hospital care due to coronary artery disease decreased significantly thereafter. The total cost of SCS procedure was recovered within 16 months after implantation, which is less than 40% of the device life span.

CONCLUSIONS

This retrospective study indicates that SCS treatment alleviates angina symptoms and improves quality of life. The treatment is also effective in preventing hospitalisations and saving costs in hospital care. A prospective study is warranted to confirm the current observations.

Thoracic spinal cord stimulation reduces the risk of ischemic ventricular arrhythmias in a postinfarction heart failure canine model

BACKGROUND

Thoracic spinal cord stimulation (SCS) is a promising therapy in treating refractory angina. This study was designed to investigate SCS with regard to the risk of arrhythmias during myocardial ischemia and its cardiac electrophysiological effects.

METHODS AND RESULTS

We studied 22 dogs with healed anterior myocardial infarction (MI) and superimposed heart failure (HF) induced by rapid ventricular pacing. SCS was applied at the dorsal T1-T2 segments of the spinal cord (at 50 Hz, 0.2 ms) for 15 minutes. Transient (2-minute) myocardial ischemia was induced on 2 separate occasions (no SCS and SCS) to provoke ventricular arrhythmias (ventricular tachycardia/ventricular fibrillation; VT/VF). Ischemic episodes were separated by 90 minutes, and dogs were randomly assigned to receive SCS or no SCS before the first or second ischemic episode. SCS reduced the occurrence of VT/VF from 59% to 23% when SCS was applied during transient myocardial ischemia (odds ratio, 0.36; 95% confidence interval, 0.1626 to 0.5646; P=0.0009). SCS also decreased sinus rate by 7.5+/-14 bpm (P=0.048), increased the PR interval by 11.1+/-14.7 ms (P=0.009), and reduced systolic blood pressure by 9.8+/-13.6 mm Hg (P=0.02).

CONCLUSIONS

Thoracic SCS appears to protect against ischemic VT/VF in a canine model of healed MI and HF. SCS reduced sinus rate and systolic blood pressure, changes consistent with the previously known antisympathetic effect of SCS, which may have contributed to the antiarrhythmic benefits.

Symptomatic relief precedes improvement of myocardial blood flow in patients under spinal cord stimulation

Background

Spinal cord electrical stimulation (SCS) has shown to be a treatment option for patients suffering from angina pectoris CCS III-IV although being on optimal medication and not suitable for conventional treatment strategies, e.g. CABG or PTCA. Although many studies demonstrated a clear symptomatic relief under SCS therapy, there are only a few short-term studies that investigated alterations in cardiac ischemia. Therefore doubts remain whether SCS has a direct effect on myocardial perfusion.

Methods

A prospective study to investigate the short- and long-term effect of spinal cord stimulation (SCS) on myocardial ischemia in patients with refractory angina pectoris and coronary multivessel disease was designed. Myocardial ischemia was measured by MIBI-SPECT scintigraphy 3 months and 12 months after the beginning of neurostimulation. To further examine the relation between cardiac perfusion and functional status of the patients we measured exercise capacity (bicycle ergometry and 6-minute walk test), symptoms and quality of life (Seattle Angina Questionnaire [SAQ]), as well.

Results

31 patients (65 ± 11 SEM years; 25 male, 6 female) were included into the study. The average consumption of short acting nitrates (SAN) decreased rapidly from 12 ± 1.6 times to 3 ± 1 times per week. The walking distance and the maximum workload increased from 143 ± 22 to 225 ± 24 meters and 68 ± 7 to 96 ± 12 watt after 3 months. Quality of life increased (SAQ) significantly after 3 month compared to baseline, as well. No further improvement was observed after one year of treament. Despite the symptomatic relief and the improvement in maximal workload computer based analysis (Emory Cardiac Toolbox) of the MIBI-SPECT studies after 3 months of treatment did not show significant alterations of myocardial ischemia compared to baseline (16 patients idem, 7 with increase and 6 with decrease of ischemia, 2 patients dropped out during initial test phase). Interestingly, in the long-term follow up after one year 16 patients (of 27 who completed the one year follow up) showed a clear decrease of myocardial ischemia and only one patient still had an increase of ischemia compared to baseline.

Conclusion

Thus, spinal cord stimulation not only relieves symptoms, but reduces myocardial ischemia as well. However, since improvement in symptoms and exercise capacity starts much earlier, decreased myocardial ischemia might not be a direct effect of neurostimulation but rather be due to a better coronary collateralisation because of an enhanced physical activity of the patients.

Spinal cord activation differentially modulates ischaemic electrical responses to different stressors in canine ventricles

Spinal cord stimulation (SCS) represents an acceptable treatment modality for patients with chronic angina pectoris refractory to standard therapy, but its mechanism of action remains unclear. To develop an experimental paradigm to study this issue, ameroid (AM) constrictors were implanted around the left circumflex coronary artery (LCx) in canines. Six weeks later, unipolar electrograms were recorded from 191 sites in the LCx territory in the open-chest, anesthetized state under basal pacing at 150 beats/min. We investigated the effect of SCS on ST segment displacements induced in the collateral-dependent myocardium in response to two stressors: (i) transient bouts of rapid ventricular pacing (TRP: 240/min for 1 min) and (ii) angiotensin II administered to right atrial neurons via their coronary artery blood supply. ST segment responses to TRP consisted of ST segment elevation in central areas of the LCx territory and ST depression at more peripheral areas. Such responses were unchanged when TRP was applied under SCS. Shortening of repolarization intervals in the metabolically compromised myocardium in response to TRP was also unaffected by SCS. In contrast, ST segment responses to intracoronary angiotensin II, which consisted of increased ST elevation, were attenuated by SCS in 6/8 preparations. The modulator effects of SCS were greatest at sites at which the greatest responses to angiotensin II occurred in the absence of SCS. These data indicate that spinal cord stimulation may attenuate the deleterious effects that stressors exert on the myocardium with reduced coronary reserve, particularly stressors associated with chemical activation of the intrinsic cardiac nervous system.

An investigation into the 'carry over' effect of neurostimulation in the treatment of angina pectoris

Neurostimulation, by way of transcutaneous electrical nerve stimulation (TENS) and spinal cord stimulation, improves signs and symptoms of myocardial ischaemia, with evidence (from non-randomised studies) that this effect extends beyond the period of stimulation itself ('carry-over' effect). In this randomised controlled trial, 10 patients underwent baseline treadmill-exercise-testing (TET), followed by two further tests at fortnightly intervals. TENS was compared to placebo in a randomised fashion. TENS produced a significant increase in total exercise time (399.3 vs. 364.5 s, p < 0.05) and time to maximum ST depression (374 vs. 324 s, p = 0.01) without a significant difference in the maximum degree of ST depression (2.0 vs. 2.1 mm, p = NS). Rate-pressure product at peak exercise was not significantly different (197 vs. 193, p = NS). TENS produced a nonsignificant change in time to onset of angina (352 vs. 325 s, p = 0.07). Pre-treatment with TENS produces a significant improvement in exercise tolerance and measures of ischaemia but not significant improvement in symptoms.

Safety and efficacy of spinal cord stimulation for the treatment of chronic pain: a 20-year literature review

OBJECT

The purpose of this report was to examine the available literature to determine the safety and efficacy of spinal cord stimulation (SCS) for the treatment of chronic pain of the trunk and limbs.

METHODS

The author identified 68 studies that fulfilled the efficacy inclusion/exclusion criteria, grouped on the basis of pain indication, with an overall population of 3679 patients. Fifty-one studies fulfilled all safety inclusion/exclusion criteria. Based on the literature review, the author found that SCS had a positive, symptomatic, long-term effect in cases of refractory angina pain, severe ischemic limb pain secondary to peripheral vascular disease, peripheral neuropathic pain, and chronic low-back pain, and that, in general, SCS was a safe and effective treatment for a variety of chronic neuropathic conditions.

CONCLUSIONS

Despite the positive findings, there is an urgent need for randomized, controlled, long-term studies on the efficacy of SCS involving larger patient sample sizes.