Spinal Cord Stimulation in the Treatment For Angina Pectoris

The number of heart transplants in Australia are increasing with a nationwide total of 63 conducted in 2007. With the increasing success of heart transplants and improving immunosuppressant therapy, the life expectancies and quality of life of transplant patients are increasing. However this presents its own set of complications; as time after heart transplant increases so does the incidence of cardiac allograft vasculopathy (CAV) with as many as 50% of transplant patients developing CAV 5 years after the transplant.

CAV is a progressive form of coronary arteriosclerosis that is highly predictive of further cardiac events. Treatment options for CAV are limited and often the patient will require another heart transplant. Re-transplantation presents obvious problems namely the limited supply of organ donors and the long waiting list. Also there is a diminished success of secondary transplant. The symptoms of CAV include inflammation of the coronary arteries and endothelial dysfunction leading to arterial narrowing. As a result, CAV can cause the extremely painful angina pectoris in affected individuals.

Angina pectoris is a suffocating pain coming from the middle of the chest often brought about by exercise or emotional stress. In most cases angina pectoris can be treated with medications or revascularisation procedures. A revascularisation procedure involves re-establishing the blood supply to the heart using a coronary bypass graft. Sometimes these interventions are not successful or cannot be undertaken due to the risks involved, for these patients the angina pectoris is said to be refractory.

Spinal cord stimulation (SCS) is now a well-established treatment for angina pectoris. SCS has been used in pain management for the last 30 years to treat chronic pain that is not responsive to less invasive treatment options such as medication and physiotherapy. SCS involves the implantation of a number of electrodes at certain positions on the spinal cord. The electrodes are connected to a lead that delivers electrical stimulation in the form of pulses from a power source, often a battery pack. By stimulating spinal nerves, pain signals to the brain are thought to be inhibited hence creating paraesthesia of the area. Currently only refractory angina patients are eligible for SCS.

SCS is not subsidised under the Medicare Benefit Scheme, however the long term benefits of SCS including; decreased medication, hospitalisation costs and further operations, present SCS as a cost effective surgery. A retrospective study published in 2004 found that the cost of the implantation was recovered within 16 months after the surgery through the significant reduction of hospitisation costs alone.

Professor Allan Merry, Head of the Anaesthesiology Department at the University of Auckland and co-author of the case study said “I believe SCS is cost effective and several studies have supported this view.”

This case study, published in Anaesthesiology Intensive Care, is the second study to show that SCS provides excellent pain relief for a refractory angina pectoris patient. The case presents a patient with severe CAV struggling with intense and frequent chest pains that are not responsive to medications. The patient underwent a SCS trial with outstanding improvements in quality of life. The authors believe that refractory angina pectoris will become more common with the increasing number of heart transplants and therefore aim to present SCS as a major consideration for its treatment in the future.

The patient was a 45-year old male who had undergone both heart and kidney transplants. Seven years after transplantation he suffered a silent myocardial infarction (heart attack); on investigation the coronary angiogram revealed he had developed severe CAV. The patient was approved for heart re-transplantation. During the wait for the heart, the patient experienced:

• Up to six attacks of chest pain per day rated 10/10 on a visual pain scale
• Similar pain he was experiencing before he had his first heart transplantation
• No relationship between the angina pectoris pain and emotional or physical exertion, hence no way to avoid it

In order to control the pain the patient spent a total of 58 days in hospital in six months. By this stage tolerance had developed to the nitrates which he initially responded positively to. The patient then began opioid treatment. None were completely effective in treating the pain.

The patient was diagnosed with chronic refractory angina pectoris with severe CAV; chest pain experienced due myocardial ischaemia as a result of CAV.

This patient’s CAV was so severe that coronary revascularisation was not a safe option and therefore this patient was accepted for a 10 day SCS trial.

The lead was inserted into the spinal cord at T1. T1 is the first thoracic level of the vertebrae. Immediate paraesthesia of the chest area was achieved. The procedure immediately yielded considerable pain relief. This patient unfortunately became susceptible to one of the risk factors associated with lead implantation, infection. The lead was then removed which correlated with an onset of chest pain. Once the infection had cleared up, the lead was implanted again and left as a permanent lead.

During the following six months the patient reported improved quality of life, increased physical activity and significant improvement of pain control. He was able to cease opioid use and reported that the SCS was a very worthwhile procedure.

This case study, along with many other recent investigations, presents SCS as a very worthwhile and viable option for angina pectoris patients.

As the number of surviving heart transplant patients increases there will be a rise in the incidence of CAV and with this will come an increasing need for greater pain management options. Re-transplantation has multiple hurdles, risk-factors and, most evidently, time constraints. Re-transplantation is often an ethically insufficient option due to the increased mortality rate with second transplantation and the limited supply of donors; as a result many patients with CAV will simply not have the option of re-transplantation.

Although SCS is thought to be one of the most effective and safe pain-management treatment procedures this case study also highlights the risk of infection at the implant insertion site. Monitoring for infection will be especially important in transplant patients currently on immunosuppressant therapy, made evident in this case.

Although SCS is very successful in treating pain it is not used as a first-line treatment and cannot be used to prevent pain.

Professor Allan Merry said “I would not use SCS for a patient post heart transplant who did not already have chest pain in order to try to prevent angina; this therapy provides symptomatic control and would not be of value until the pain developed.”

This is one of many cases presenting SCS as an effective and definite treatment for angina pectoris and the second study to show that SCS is also effective in refractory angina. This case study aimed to add to the growing support of SCS as a consideration for treatment of this condition.

References

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