Review Article
Effect of Spinal Cord Stimulation in Patients With Refractory Angina: Evidence From Observational Studies

https://doi.org/10.1111/j.1525-1403.2012.00430.xGet rights and content

Objectives

To review the evidence in observational studies of the effect of spinal cord stimulation (SCS) in patients with refractory angina pectoris (RAP) due to obstructive coronary artery disease. The effect of SCS in patients with refractory microvascular angina (MVA) also was assessed.

Materials and Methods

We reviewed the observational studies, published from 1987 to 2010, which investigated the effects of SCS on RAP. The number of angina attacks and that of taken nitrate tablets, as well as the class of angina, were considered as main outcome variables. The occurrence of adverse events related to the treatment also was assessed.

Results

The results showed a consistent reduction of the number of angina attacks (by 45–84%) and of consumption of short-acting nitrate tablets (by −75% to −94%), whereas the New York Heart Association and Canadian Cardiovascular Society class of angina were significantly improved in some studies. No case fatalities related to the therapy were reported. Significant clinical benefits were observed in some studies in patients with refractory MVA. Device-related infections and catheter dislodgment were the most significant and frequent side-effects, respectively.

Conclusions

In observational studies, SCS showed to be an effective form of treatment for RAP, including refractory MVA. The treatment appears to be safe both at short- and long-term follow-up.

Section snippets

INTRODUCTION

Refractory angina pectoris (RAP) is a chronic clinical condition characterized by the following: 1) frequent angina attacks resulting in a marked limitation of ordinary physical activity or even in inability to carry out any activity without discomfort (Canadian Cardiovascular Society angina class III-IV); 2) inefficacy of maximally tolerated medical therapy in sufficiently preventing angina symptoms; 3) documentation at angiography of obstructive coronary artery disease (CAD) judged unsuitable

SCS: TECHNIQUE AND MECHANISMS

SCS involves the insertion of a quadripolar (or even octopolar) lead wire in the epidural space through puncture, usually of the T5-T6intervertebral space, advancing the tip of the lead at the level of C7-T1. The epidural lead is connected through subcutaneous tunneling of an extension wire to an internal programmable generator (IPG), which is usually implanted in a subcutaneous abdominal wall pocket (one-session implant). A magnetic handheld control device turns the unit on and off and adjusts

THE ISSUE OF PLACEBO-CONTROLLED STUDIES OF SCS IN RAP

It was until recently believed that a requisite for SCS to achieve optimal therapeutic effect is the induction of paresthesia that should cover ≥80% of the area of the chest where angina pain is referred (1,3). The paresthesic sensation is a clue that the therapy is working and, at the same time, that it is stimulating the right spinal segments, where neurons carry the cardiac pain stimuli.

The need of paresthesic stimulation to achieve the therapeutic effect has until now precluded the

OBSERVATIONAL VS. RANDOMIZED PLACEBO-CONTROLLED TRIALS

Current recommendations of treatment of medical diseases are rightly mainly based on the results of randomized placebo-controlled trials (RPCTs), which provide the best evidence for the true efficacy of the therapy. Some merits of well-conducted prospective observational studies, however, should not be denied and, when concordant about the clinical benefits of a treatment, should be taken into appropriate account, at least until a more convincing demonstration of efficacy is obtained through

OBSERVATIONAL STUDIES OF SCS IN RAP PATIENTS

The possibility to use SCS to treat angina was first suggested by Sandric et al. in 1984 at our institute (33). These authors, indeed, noticed that a few patients with ischemic heart disease, who had received SCS to treat severe obstructive peripheral artery disease, showed improvement not only of peripheral symptoms but also of their angina attacks.

Some years later, Murphy and Giles reported the results of the first series of patients who were specifically treated with SCS for angina (34).

SAFETY

An important information deriving from observational studies of SCS in RAP is the consistency of the lack of fatality cases and also of major complications, causing persistent or severe debilitation, associated with SCS therapy, both at short- and long-term follow-up, which puts the treatment in a very favorable risk/benefit ratio, although some bothersome side-effects can occur.

The most frequent side-effects and complications reported in the selected studies, when available, are summarized in

SCS AND THE ISSUE OF ISCHEMIC PAIN INHIBITION

Precordial pain is the cardinal alarming symptom of myocardial ischemia, which prompts the patient to take the appropriate interventions (e.g., stopping effort, taking sublingual NTG, or recur to physicians) to avoid negative, life-threatening consequences.

An issue that has been raised with SCS therapy is the possibility that effective pain relief by SCS might conceal the alarming symptom of ongoing severe myocardial ischemia, such as, in particular, in case of acute myocardial infarction, thus

SCS IN PATIENTS WITH MVA

While obstructive CAD is the usual cause of angina, and even of RAP, in a number of patients with chest pain typical enough to suggest significant CAD and with evidence of myocardial ischemia on noninvasive stress tests, coronary angiography surprisingly shows normal coronary arteries. A dysfunction of small coronary arteries has been documented in most of these patients, who are therefore diagnosed as having MVA (52). Although the prognosis of MVA is excellent, a significant number of patients

CONCLUSIONS

In observational studies, SCS has consistently been shown to be an effective form of treatment for RAP, including refractory MVA. The treatment appears to be safe both at short- and long-term follow-up. It should be recognized that further placebo-controlled studies are mandatory to obtain definite proofs of its clinical efficacy and that appropriate studies also should establish pros and cons of SCS compared with other forms of therapy, including the promising subcutaneous electrical nerve

Authorship Statements

Dr. Barone and Dr. Di Monaco reviewed in detail and summarized all articles for the review. They also prepared the figures and summary tables. They discussed each article in detail with the first author. Dr. Lanza conceived the review, guided the review work, and wrote the manuscript, which was approved by the co-authors.

How to Cite This Article:

Lanza G.A., Barone L., Di Monaco A. 2012. Effect of Spinal Cord Stimulation in Patients With Refractory Angina: Evidence From Observational Studies. Neuromodulation 2012; 15: 542–549

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