Key points

Introduction

Peripheral vascular disease (PVD) is a common disease mostly involving arteries of the extremities. It usually results from progressive narrowing of arteries in the lower extremities, caused by atherosclerosis. PVD prevalence in the United States has ranged as high as 30% in adult populations and is closely associated with elevated risk of cardiovascular disease morbidity and mortality. It is estimated that by 2020, 7 million people aged older than 40 years will suffer from PVD. Severe limb pain, claudication, ulcerations, and limb amputation are common complications of PVD, especially among patients with kidney disease and diabetes. The universal treatment approach for PVD includes risk-factor modification, pharmacologic therapy, and revascularization.

Early in the 1980s, individuals with refractory ischemic pain attributed to PVD were treated with spinal cord stimulation (SCS). Since then, multiple studies have shown proved efficacy of SCS in PVD. Other studies inquired into the pathophysiology and mechanism of action; the changes in tissue oxygenation and blood flow were considered as markers for response. It was also consistently shown that SCS significantly improved multiple outcomes, such as exercise tolerance, limb salvage, and pain level in patients presenting with critical leg ischemia.

This article describes the role of SCS in the treatment of PVD, the patient selection criteria along with the outcomes, and mechanism by which SCS works in PVD.

Introduction

Peripheral vascular disease (PVD) is a common disease mostly involving arteries of the extremities. It usually results from progressive narrowing of arteries in the lower extremities, caused by atherosclerosis. PVD prevalence in the United States has ranged as high as 30% in adult populations and is closely associated with elevated risk of cardiovascular disease morbidity and mortality. It is estimated that by 2020, 7 million people aged older than 40 years will suffer from PVD. Severe limb pain, claudication, ulcerations, and limb amputation are common complications of PVD, especially among patients with kidney disease and diabetes. The universal treatment approach for PVD includes risk-factor modification, pharmacologic therapy, and revascularization.

Early in the 1980s, individuals with refractory ischemic pain attributed to PVD were treated with spinal cord stimulation (SCS). Since then, multiple studies have shown proved efficacy of SCS in PVD. Other studies inquired into the pathophysiology and mechanism of action; the changes in tissue oxygenation and blood flow were considered as markers for response. It was also consistently shown that SCS significantly improved multiple outcomes, such as exercise tolerance, limb salvage, and pain level in patients presenting with critical leg ischemia.

This article describes the role of SCS in the treatment of PVD, the patient selection criteria along with the outcomes, and mechanism by which SCS works in PVD.

Review of published literature

Electrical stimulation of the posterior column (SCS) was first introduced in the late 1960s. It is thought to be based on the “gate-control” theory of pain described in 1965 by Melzack and Wall. It is generally used for the treatment of pain and is currently an established treatment of neurogenic pain. It was not until 1976 when Cook and colleagues introduced SCS as a therapeutic option for vascular disease of the limbs. Since then, multiple studies were done to prove and assess the efficacy of SCS for the treatment of PVD ( Table 1 ).

One of the large prospective, controlled studies was the Spinal Cord Stimulation European Peripheral Vascular Disease Outcome Study. The aim of the study was to evaluate the outcome of SCS on limb survival in individuals with critical leg ischemia. It concluded that SCS provided a significantly better limb survival rate than conservative treatment. In this study, the transcutaneous oxygen pressure (TcPO2), which is associated with high amputation rate, was assessed in 71 patients with PVD. Based on this prospective controlled study, the authors concluded that SCS provided a significantly better limb survival rate than conservative treatment. After a 12-month follow-up, limb survival was 33% higher in the patients treated with SCS. It was also shown that pain was significantly reduced in the SCS-treated group.

Jivegard and colleagues studied 51 patients presenting with atherosclerotic and diabetic limb ischemia. In this prospective, randomized, controlled study that followed patients for 18 months, there was no difference in microcirculation between the SCS and control groups. Nevertheless, the group of patients treated with SCS had better pain relief and significantly higher rate of limb salvage. In the same study, it was also noted that the most significant benefit from SCS was among those with inoperable limb ischemia and those presenting with arterial hypertension.

Tallis and colleagues reported a case series of 10 patients presenting with severe, intractable symptoms of arteriographically proved arteriosclerosis and vascular ischemia. Some of the patients also demonstrated nonhealing ulcers and claudication. The authors measured cutaneous blood flow and muscle blood flow (by measuring Xenon 133 clearance). All patients had SCS trial before implantation of a permanent epidural SCS device. In this study all 10 patients showed improvement in mean claudication distance and improvement in the bicycle ergometer tolerance exercise. Most of the patients showed improvement in ischemic limb pain and ulcer healing. After SCS, there was a remarkable increase in the cutaneous blood flow and in the measured muscle blood flow within the group of patients that had positive clinical response to the SCS.

Reig and Abejon reported their 20 years of experience with 98 SCS implants in patients presenting with PVD. The authors measured clinical response, relief of pain, and ulcer healing. Almost 88% of the patients showed good clinical response with SCS. In this big retrospective cohort study, the authors concluded that SCS should be a therapeutic approach in treating PVD. Good pain relief was reported in more than 85% of the patients and most patients also reported improvement of their ischemic symptoms.

An important study was done among a group of patients with end-stage renal disease by Brummer and colleagues. The importance of the study was defined by the fact that these patients were not candidates for limb-preservation surgeries and not considered to benefit from any revascularization procedures. Intensity of ischemic pain, quality of life, use of analgesic medications, limb survival, and outcome of skin ischemic lesions were evaluated before implantation of an SCS and at 6 and 12 months of follow-up. Of the eight patients that were studied, all showed significant improvement in pain, quality of life, limb survival, and absence of new skin ulcer development. This dynamic was most prominent in patients assessed at Fontaine stage III and IV.

The Dutch multicenter randomized controlled study followed 120 patients presenting with critical leg ischemia. In this study, Ubbink and colleagues investigated the cutaneous microcirculation by means of capillary microscopy, laser Doppler perfusion, and transcutaneous oxygen measurements in the foot. The minimum follow-up period was 18 months. The authors reported that amputation frequency was higher in those patients with poor microcirculation and lower in those with good skin perfusion. In this important study, it was shown that in the group of patients with intermediate microcirculation SCS provided better chance for limb survival.

Kumar and colleagues prospectively studied 39 patients with nonreconstructable ischemic vascular lower extremity disease. All patients had a successful SCS trial. The average follow-up was 21 months, and the analyzed parameters included pain control, microcirculatory changes measured by means of TcPO2, blood flow velocities, and pulse volumes. They concluded that SCS provides benefits as measured by TcPO2, blood flow velocities, and pulse volumes and improves microcirculation and macrocirculation.

In their retrospective study of 258 patients treated with SCS, Horsch and colleagues followed the patients for a period of 18 months. All patients had to meet the following criteria: baseline TcPO2 less than 20 mm Hg, noncandidates for reconstructive surgery, and not treated with any medications for the PVD. The authors concluded that among the group of patients presenting with a low baseline TcPO2 (<10 mm Hg), limb survival was significantly improved. They also showed that patients treated with SCS had ischemic pain relief and improvement in microcirculation. This study led to a conclusion that baseline TcPO2 could serve as a predictor for SCS treatment outcome.

In their critical review of the literature, Ubbink and Vermeulen summarized reports of nearly 450 patients in six studies. Based on this, they concluded that limb salvage after 12 months follow-up period was higher within the group of patients that were treated with SCS. Pain relief was also higher in the SCS patient group, and the need for analgesics and other pain relief medications was significantly lower. However, there was no significant statistical difference in ulcer healing.