Effective angina pectoris therapy remains on the shelf: Why aren’t medical practitioners using spinal cord stimulation?

Spinal cord stimulation (SCS) is an off-label adjunct treatment for refractory angina pectoris (AP). There is evidence to suggest that this method may be effective for reducing pain and physical impairment and improving quality of life (QoL) amongst patients with AP who fail to respond to pharmacological and surgical therapies.1

Despite evidence supporting the use of SCS for refractory AP, awareness of the treatment amongst medical practitioners and patients is low. There is discordance between the evidence base and medical practitioners’ willingness to trial SCS in refractory AP patients who fail to respond to other therapies.²

A prevalent, severe and debilitating condition

Angina pectoris (AP) – that is, angina caused by insufficient coronary blood flow – is a common condition affecting 6.7% of women and 5.7% of men. A considerable proportion of these patients (5–10%) develop refractory AP – that is, AP with comorbid coronary artery disease which is uncontrollable with standard clinical therapies.¹

Standard treatments for the conditions include pharmacotherapy with anti-anginals or nitrates, and surgical interventions including revascularisation by angioplasty, coronary stents and coronary artery bypass surgery.²

Suffocating chest pain impairs physical movement

The key symptom of AP is suffocating chest pain during physical exertion. For example, AP may cause pain that is so severe a patient cannot climb a flight of stairs. The condition therefore significantly impairs physical abilities.² In some cases, pain also occurs in response to stress.³

In other cases, chronic, debilitating pain occurs in the absence of physical exertion or stress and is so severe it requires hospitalisation and incurs significant health system costs. One case report detailed a male patient who, over a six month period, spent 58 days in hospital for pain treatment associated with refractory AP.³

Electrical pulses relieve pain

SCS is a neurological treatment that can relieve symptoms in patients with refractory AP. It involves implantation of a spinal stimulation device with an electric pulse generator into the upper spine (epidurally, usually at or near T1).¹

By stimulating spinal nerves with electrically generated pulses, the device generates paraesthesias which inhibit transmission of pain signals to the brain.⁴ This is the key mechanism through which SCS is thought to relieve pain associated with angina. Another possible mechanism is by exerting anti-angina effects via its anti-ischaemic activity.¹

SCS is a safe, effective and cost-effective treatment for AP

Physical impairment is the key reason for declining QoL in refractory AP patients, and relieving pain is associated with QoL improvement in most patients. These patients are candidates for adjunct therapies that can relieve pain, of which SCS is one with proven safety and efficacy.¹

SCS was first used for pain relief in AP in 1987.⁵ Since then, over 2,000 patients have received the therapy to relieve AP-associated pain.² Long-term research has shown that the majority of patients (at least 80%) experience benefits, including reduced need for nitroglycerin, reduced angina attacks, improved physical mobility and improved QoL.² It also reduced the rate of hospitalisation and duration of hospital stays.⁵ The treatment reduces associated pain, without complicating the recognition of adverse cardiac events such as myocardial infarction.^1,2,5

Research has also shown that SCS is comparable with invasive coronary artery bypass surgery in terms of reducing pain, increasing coronary blood flow and reducing future myocardial infarction incidence in patients with medically intractable angina. In addition, it is associated with significantly reduced morbidity and mortality, making it a superior treatment. Trials are yet to compare the efficacy of angioplasty and SCS.²

Local experience with SCS

SCS is considered a cost effective and feasible treatment option in Australia⁵ and New Zealand.⁶ In New Zealand, where SCS has been used to treat angina since 1997, a study found that although initial treatment costs are high, cost savings occur after about 15 months of treatment because the treatment reduces patient contact with the health system.⁶

In Australia, SCS costs around AU$15,000 per patient and is considered a cost effective short-to-medium term palliative treatment in the general population of refractory AP patients. It has been suggested that SCS is a practical therapeutic option that should be used to treat AP more often than it is.⁵

Comorbid conditions limit the efficacy of SCS

There are some significant differences in patient response to SCS. While the majority improve with SCS, 20–30% of patients do not experience long-term QoL improvements.¹ Further research is needed to elucidate the characteristics of patients who are most likely to respond to SCS and of non-responders who are more likely to benefit from a different treatment.²

One study reported that comorbid conditions, including diabetes, excessive BMI and coronary obstructive pulmonary disease, were risk factors for non-response to SCS, and also that SCS was more effective in men than women. The small study suggested that the benefits of SCS may be impaired when comorbidities continue to exert an effect on QoL, and that with proper targeting of patients, effectiveness could be further improved.¹

SCS is rarely used to treat AP

SCS is approved for the treatment of AP in Europe. However, it remains an off-label treatment in the United States² and a relatively unknown and/or underutilised method for treating AP in the US² and Australia.⁵

Medical practitioners often lack knowledge and education about SCS, which may reduce its use. Because the treatment is off-label, manufacturers are not permitted to market and raise awareness about SCS devices, and patients are unable to receive insurance rebates because the treatment is classified as experimental.²

Entrenched patterns of clinical practice may also play a role in the limited use of SCS. While the technique is used in cardiac rhythm management, it is a novel method of treating AP which, unlike other treatments, targets both pain and coronary blood flow. However, SCS patients require referral to a neuromodulation specialist, and general practitioners may be more familiar with referring cases of refractory AP to cardiologists.²

Increasing awareness

Overcoming these barriers to SCS use would provide another treatment option for refractory AP patients and increase their chances of receiving optimal therapy.² As SCS device manufacturers are unable to raise awareness of their products amongst treating doctors, professional societies and associations must play a role in raising awareness of this treatment technique and its efficacy.²

SCS is an effective treatment which has been demonstrated beneficial for Australian patients with refractory AP.⁵ Considerable health system cost savings and patient benefits can be expected with the expanded use of SCS in the treatment of AP.²

References

Jitta DJ, DeJongste MJL, Kliphuis CM, Staal MJ. Multimorbidity, the predominant predictor of quality-of-life, following successful spinal cord stimulation for angina pectoris. Neuromodulation. 2011;14(1):13-9. [Abstract]
Levy RM. Spinal cord stimulation for medically refractory angina pectoris: Can the therapy be resuscitated? Neuromodulation. 2011;14(1):1-5. [Abstract]
Singh H, Merry AF, Ruygrok R, Ruttley A. Treatment of recurrent chest pain in a heart transplant recipient using spinal cord stimulation. Anaesth Intensive Care. 2008;36(2):242-4. [Abstract]
Middleton P, Simpson B, Maddern G. Spinal cord stimulation (neurostimulation): An accelerated systematic review. ASERNIP-S. 2003;43:1-32. [Abstract | Full text]
Chua R, Keogh A, Spinal cord stimulation significantly improves refractory angina pectoris: A local experience spinal cord stimulation in refractory angina. Heart Lung Circ. 2005;14(1);3-7. [Abstract]
Merry A. Spinal cord stimulation for angina pectoris. Proceedings of the Australia and New Zealand College of Anaesthetists Annual Scientific Meeting; 7-11 May 2005; Auckland, NZ. [Abstract]