Spinal cord stimulation for the treatment of refractory angina pectoris: a two-year follow-up

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.

Spinal Cord Stimulation for Refractory Angina Pectoris: A Systematic Review and Meta-analysis

Objectives:

Paresthesia-free stimulation such as high frequency and burst have been demonstrated as effective therapies for neuropathic pain. The aim of this meta-analysis was to evaluate the efficacy and safety of conventional spinal cord stimulation (SCS) in the treatment of refractory angina pectoris (RAP).

Materials and Methods:

Relevant randomized controlled trials that investigated SCS for patients with RAP were comprehensively searched in Medline, Pubmed, Embase, and Cochrane Library. Five meta-analyses were performed examining the changes in Canadian Cardiovascular Society classes, exercise time, Visual Analog Scale (VAS) scores of pain, Seattle Angina Questionnaire, and nitroglycerin use in RAP patients after SCS therapy. We analyzed standardized mean differences (MD) and 95% confidence intervals (CIs) for each outcome by Review Manager 5.0 and STATA 12.0.

Results:

A total of 12 randomized controlled trials involving 476 RAP patients were identified. A trend of reduction in the angina frequency (MD=−9.03, 95% CI, −15.70 to −2.36) and nitroglycerin consumption (MD=−0.64, 95% CI, −0.84 to −0.45) could be observed in the SCS group. Compared with the control group, SCS showed benefit on increasing exercise time (MD=0.49, 95% CI, 0.13-0.85) and treatment satisfaction (MD=6.87, 95% CI, 2.07-11.66) with decreased VAS scores of pain (MD=−0.50, 95% CI, −0.81 to −0.20) and disease perception (MD=−8.34, 95% CI, −14.45 to −2.23). However, the result did not reach the significance level in terms of physical limitation (95% CI, −8.75 to 3.38; P=0.39) or angina stability (95% CI, −7.55 to 3.67; P=0.50).

Discussion:

The current meta-analysis suggested that SCS was a potential alternative in the treatment of PAP patients. Further investigation for finding the appropriate intensity of stimulation is required before this treatment should be widely recommended and applied.

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.

Dorsal column stimulator applications

Background:

Spinal cord stimulation (SCS) has been used to treat neuropathic pain since 1967. Following that, technological progress, among other advances, helped SCS become an effective tool to reduce pain.

Methods:

This article is a non-systematic review of the mechanism of action, indications, results, programming parameters, complications, and cost-effectiveness of SCS.

Results:

In spite of the existence of several studies that try to prove the mechanism of action of SCS, it still remains unknown. The mechanism of action of SCS would be based on the antidromic activation of the dorsal column fibers, which activate the inhibitory interneurons within the dorsal horn. At present, the indications of SCS are being revised constantly, while new applications are being proposed and researched worldwide. Failed back surgery syndrome (FBSS) is the most common indication for SCS, whereas, the complex regional pain syndrome (CRPS) is the second one. Also, this technique is useful in patients with refractory angina and critical limb ischemia, in whom surgical or endovascular treatment cannot be performed. Further indications may be phantom limb pain, chronic intractable pain located in the head, face, neck, or upper extremities, spinal lumbar stenosis in patients who are not surgical candidates, and others.

Conclusion:

Spinal cord stimulation is a useful tool for neuromodulation, if an accurate patient selection is carried out prior, which should include a trial period. Undoubtedly, this proper selection and a better knowledge of its underlying mechanisms of action, will allow this cutting edge technique to be more acceptable among pain physicians.

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.

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.

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 for chronic intractable angina pectoris: a unified theory on its mechanism

The use of spinal cord stimulation (SCS) for chronic intractable anginal pain was first described in 1987. Numerous studies have demonstrated its efficacy in improving exercise tolerance, decreasing frequency of anginal episodes, and prolonging time to electrocardiographic signs of ischemia. This review will examine the potential mechanisms of this antianginal effect and propose a unified hypothesis explaining it. The effect of SCS involves a mutual interaction of decreased pain, decreased sympathetic tone, and a likely redistribution of myocardial blood flow to ischemic regions. Spinal cord stimulation reduces the transmission of nociceptive impulse via the spinothalamic tract due to an enhanced release of gamma aminobutyric acid (GABA) from dorsal horn interneurons. Improvement of myocardial blood flow at the microvascular level has been demonstrated by positron emission tomography (PET). A decreased sympathetic tone has been shown by norepinephrine kinetics, tests of sympathetic reflexes, and the use of ganglionic blockers. We hypothesize that SCS exerts its beneficial effects by decreasing pain and decreasing sympathetic tone, the result of which is decreased myocardial oxygen consumption along with an improved myocardial microcirculatory blood flow.

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.

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 Patients With Refractory Angina and Previous Coronary Surgery

BACKGROUND

Refractory angina pectoris is an exceptionally debilitating condition affecting patients who have typically failed multiple percutaneous and surgical revascularizations and optimal medical therapy and who are not amenable for further revascularization procedures. Spinal cord stimulation (SCS) has been adopted in this context at our institution and midterm mortality, anginal status, and quality of life have been evaluated.

METHODS

From 1998 to 2004, 51 patients with refractory class III-IV angina, who were not considered candidates for revascularization procedures, underwent SCS. All patients had already undergone previous surgical revascularization and a median of two percutaneous procedures. Transmyocardial laser revascularization had been previously performed in 8 cases (15.6%). Most of the patients (70.5%) had experienced a myocardial infarction. Mean ejection fraction was 0.42 +/- 0.121, Canadian Cardiovascular Society class 3.5 +/- 0.5, quality of life (Spitzer index) 4.5 +/- 1.2, and the median frequency of weekly angina episodes was 10.

RESULTS

There were no SCS implantation-related complications. At follow-up (100% complete, mean 24 +/- 18 months), a significant improvement of anginal symptoms (>50% reduction of weekly anginal episodes) occurred in 45 patients (88.2%). In those patients (Responders), the quality of life improved significantly (6.8 +/- 1.5; p < 0.0001), CCS class decreased to 2 +/- 0.7 (p < 0.0001), and the median frequency of weekly angina episodes to 3 (p < 0.0001). At 3 years, Responders' survival was 91.8 +/- 4.6% and the freedom from cardiac events 72.6 +/- 8.42%.

CONCLUSIONS

Spinal cord stimulation is a safe and effective procedure in truly no-option patients affected by refractory angina. A midterm sustained improvement of symptoms and quality of life have been documented with a satisfactory 3-year survival rate.

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.

Current medical management of chronic stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina. The coronary arteries of patients with stable angina also contain many more non-obstructive plaques, which are prone to rupture resulting in acute coronary syndrome (unstable angina, myocardial infarction, sudden ischemic death). Therefore, the medical management must use strategies which not only relieve symptoms and prolong angina free walking but also reduce the incidence of adverse clinical outcomes. Whether any of the approved antianginal drugs, nitrates, beta-blockers, and calcium channel blockers reduce the incidence of adverse clinical outcomes in patients with stable angina has not been studied to date. Published data shows that percutaneous coronary revascularization procedures and coronary bypass surgery are effective in relieving angina but these procedures do not reduce mortality or the incidence of myocardial infarction compared to anti-anginal drug therapy. From the available data, an initial trial of medical treatment with anti-anginal drugs and strategies to reduce adverse clinical outcomes (smoking cessation, daily aspirin, treatment of dyslipidemias and hypertension) is indicated in most patients with stable angina pectoris. The initial choice of drug will depend on the presence or absence of comorbid conditions. Patients who do not respond to medical therapy or do not wish to take anti-anginal drugs and whose life style is limited because of anginal symptoms should be offered percutaneous revascularization procedures with or without stent placement or coronary bypass surgery. New drug-coated stents hold promise but long-term data and large-scale trials assessing the continued long-term improvement in symptoms and reduction of adverse outcomes is needed before offering such devices to all patients with stable angina. Newer medical therapies such as metabolic modulators and sinus rate lowering drugs also hold promise but need further evaluation. Patients who have refractory angina despite optimal medical therapy and are not candidates for revascularization procedures may be candidates for some new techniques of enhanced external Counterpulsation, Spinal Cord Stimulation, sympathectomy or direct transmyocardial revascularization. The usefulness of these techniques, however, needs to be confirmed in large randomized trials.

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.

Spinal cord stimulation for the treatment of angina pectoris

Spinal cord stimulation (SCS) has been demonstrated to cause clinical improvement in patients with refractory angina pectoris in the number of anginal episodes, in nitroglycerin consumption, in maximal exercise time, in exercise time until angina, in the number of episodes of myocardial ischemia, in the duration of episodes of myocardial ischemia, and in ischemic ST-segment depression at a comparable workload. Double-blind, randomized, placebo-controlled studies have not been performed with SCS. The clinical improvement from SCS occurred despite no improvement in measured regional myocardial blood flow during exercise or in myocardial oxygen consumption as assessed by the heart rate times systolic pressure product at maximal exercise. The mechanisms of clinical improvement by SCS are unclear. SCS must be considered experimental at this time, and it remains a potential therapeutic option for the treatment of refractory angina pectoris in patients unable to have coronary revascularization or at very high risk for coronary revascularization.

Immediate and long-term clinical outcome after spinal cord stimulation for refractory stable angina pectoris

The treatment of patients with angina pectoris refractory to medical therapy and unsuitable for revascularization procedures has yet not been well standardized. Previous retrospective studies and small prospective studies have suggested beneficial effects of spinal cord stimulation (SCS) in these patients. We created a Prospective Italian Registry of SCS to evaluate the short- and long-term clinical outcome of patients who underwent SCS device implantation because of severe refractory angina pectoris. Overall, 104 patients were enrolled in the registry (70 men, aged 68 +/- 17 years), most of whom (83%) had severe coronary artery disease. Average follow-up was 13.2 +/- 8 months. Overall, 17 patients (16%) died, 8 (8%) due to cardiac death. Among clinical variables, only age was found to be significantly associated both with total mortality (p = 0.04) and cardiac mortality (p = 0.02) on Cox regression analysis. A significant improvement of anginal symptoms (> or =50% reduction of weekly anginal episodes, compared with baseline) occurred in 73% of patients, and Canadian Cardiovascular Society angina class improved by > or =1 class in 80% and by > or =2 classes in 42% of patients, with a relevant reduction in the rate of hospital admission and days spent in the hospital because of angina (p <0.0001 for both). No life-threatening or clinically serious complications were observed. The most frequent side effect consisted of superficial infections, either at the site of puncture of electrode insertion or of the abdominal pocket, which occurred in 6 patients. In conclusion, our prospective data point out that SCS can be performed safely and is associated with a sustained improvement of anginal symptoms in a relevant number of patients with refractory stable angina pectoris.

Refractory angina pectoris: mechanism and therapeutic options

As the survival of patients with primary coronary events continues to increase, the number of patients presenting with coronary artery disease unsuitable to further revascularization techniques and symptoms refractory to medical therapy also continues to rise. The aims of this review were to define the population of patients with refractory angina pectoris and to present the therapeutic options currently available for this condition. Refractory angina pectoris is defined, and traditional medical therapies are discussed. Then, current therapeutic options for patients with refractory angina are extensively reviewed. A multitude of therapeutic options exist for patients with refractory angina pectoris. Small, uncontrolled studies have shown a potential benefit for additional antiplatelet and antithrombotic therapy. In randomized trials, neurostimulation has been shown to be effective in reducing angina symptoms. Enhanced external counterpulsation is a viable treatment option for select patients with refractory angina. In many randomized trials, laser revascularization has been shown to diminish angina symptoms, although no placebo-controlled studies exist to date. Gene therapy is a promising area of research in this field. Percutaneous in situ coronary venous arterialization is in its infancy, but may be able to treat many patients if proved successful. No data support the role of chelation therapy in this population. Heart transplantation remains a final option for these patients. Further research of the techniques mentioned in this review is warranted. The importance of randomized, double-blinded, placebo-controlled trials cannot be overemphasized, as the placebo effect of these therapies is probably marked.

Spinal Cord Stimulation: A Comparison of Efficacy versus Other Novel Treatments for Refractory Angina Pectoris

Recently much attention has been directed toward novel treatment alternatives for refractory angina pectoris. Refractory angina is persistent stable class III or IV angina despite maximally tolerated medical treatment in patients with end-stage coronary artery disease. Transmyocardial laser revascularization (TMLR), gene therapy, intermittent urokinase therapy, enhanced external balloon counterpulsation, and spinal cord stimulation have all been employed to treat refractory angina pectoris. TMLR and gene therapy are invasive open-chest procedures that have yielded controversial results. Intermittent urokinase and enhanced external balloon counterpulsation studies have limited follow-up times and require multiple clinic visits for treatment. Spinal cord stimulation has a proven short- and long-term efficacy and cost-effectiveness in the treatment of refractory angina. When compared to coronary artery bypass grafting (CABG), it has been shown to decrease the frequency of anginal attacks and consumption of short-acting nitrates to the same extent in refractory angina. Spinal cord stimulation's safety profile has also been well established and it can be used concurrently with cardiac pacemakers or MRI systems, provided the proper precautions are taken. Since spinal cord stimulation is a minimally invasive procedure with a favorable efficacy and safety profile, it should be considered as a valid treatment alternative after medical management has failed in refractory angina prior to implementing invasive modalities such as TMLR or gene therapy.

Linear lesions in myocardium created by Nd:YAG laser using diffusing optical fibers: in vitro and in vivo results

BACKGROUND AND OBJECTIVE

Linear lesions may be necessary for successful catheter ablation of cardiac arrhythmias such as atrial fibrillation. This study uses laser energy delivered through diffusing optical fibers as an alternative to radiofrequency energy for the creation of linear lesions in cardiac tissue in a single application.

STUDY DESIGN/MATERIALS AND METHODS

Samples of canine myocardium were placed in a heated, circulating saline bath and irradiated with a 1.06-microm, continuous-wave Nd:YAG laser during in vitro studies. Laser ablation was then performed in vivo on the epicardial surface of the right ventricle during an open-chest procedure by using similar ablation parameters. Laser energy was delivered to the tissue by being diffused radially through flexible optical fiber tips oriented parallel to the tissue surface. Histology and temperature measurements verified transmurality, continuity, and linearity of the lesions.

RESULTS

Peak tissue temperatures measured in vitro remained low (51 +/- 1 degrees C at the endocardial surface, 61 +/- 6 degrees C in the mid-myocardium, and 55 +/- 6 degrees C at the epicardial surface) with no evidence of tissue charring or vaporization. Lesion dimensions produced in vitro and in vivo were similar (depth, 6 mm; width, 8-10 mm; length, 16-22 mm), demonstrating that tissue perfusion in vivo did not significantly alter the heating.

CONCLUSION

Long linear lesions, necessary for duplication of the surgical maze procedure during catheter ablation of atrial fibrillation, may be created by using laser radiation delivered through flexible diffusing optical fiber tips. Further development of steerable catheters for endocardial atrial ablation and studies correlating thermal damage zones with electrophysiologic indicators of irreversible conduction block are warranted.