Abstract

Background: Spinal cord stimulation (SCS) is an alternative treatment option for refractory angina. Controlled trials demonstrate symptom relief and improvement in functional status. Since patients experience retrosternal prickling during active SCS, there is no option for blinding patients to active treatment or for placebo control.

Objective: To examine the therapeutic effects of subthreshold SCS in patients with refractory angina in a placebo-controlled study.

Methods: 12 responders to treatment who had already been treated with SCS for refractory angina were enrolled. Patients were randomised into four consecutive treatment arms, each for 4 weeks, with various stimulation timing and output parameters: 3×2 h/day (phase A) and 24 h/day with conventional output (phase B); 3×2 h/day with a subthreshold output (phase C); and 24 h/day with 0.1 V output, which served as control (phase D). Functional status, quality of life, Canadian Cardiovascular Society classification and nitrate usage were assessed at the end of each 4-week period.

Results: In phase D, patients showed a significant reduction in walking distance compared with phases A and C. Canadian Cardiovascular Society classification worsened in phase D compared with phases A–C. Frequency of angina attacks and the visual analogue scale were significantly worse in phase D than in phases A–C. In three patients, it was necessary to prematurely terminate phase D owing to intolerable angina attacks.

Conclusions: In this first placebo-controlled trial to apply SCS in patients with refractory angina, improvement in functional status and symptoms was revealed in phases with conventional or subthreshold stimulation, in comparison to a low-output (placebo) phase.