Objectives The aim of this study was to examine therapeutic effects of subthreshold spinal cord stimulation (SCS) in patients with refractory angina by creating a placebo-controlled study design.
Background 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 therapy, or for placebo control.
Methods We enrolled 12 therapy responders already treated with SCS for refractory angina. Patients were randomized into 4 consecutive treatment arms, each for 4 weeks, with various stimulation timing and output parameters: 3 ,,e 2h/day (phase A) and 24h/day with conventional output (phase B); 3 ,,e 2h/day with a subthreshold output (phase C); and 24h/day with 0.1-V output, which served as control (phase D). Functional status, quality of life, CCS classification, and nitrate usage were assessed at the end of each 4-week period.
Results In phase D, patients showed significant reduction in walking distance compared to A and C. CCS class worsened in phase D compared to A, B, and C. Angina frequency and Visual Analog Scale were significantly worse in phase D compared to A, B, and C. In 3 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.
- coronary artery disease
- refractory angina
- spinal cord stimulation
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