Ten studies (n=331 patients) were included in the review: six randomised controlled trials (RCTs); two follow-ups of one of the RCTs; and two controlled studies. All of the studies were assessed as medium or high quality: four studies received scores of 4 (high quality), two received scores of 3 (medium quality) and the remaining two studies received a score of 2 (medium quality).
Spinal cord simulation versus any comparator:
Four high-quality studies (n=201) showed that, compared with control groups, spinal cord simulation led to an improvement in angina symptom scores as measured by the number of angina attacks, consumption of nitrates and/or improvement of angina severity as measured by the Canadian Cardiovascular Society scale. The same four studies indicated that spinal cord simulation improved functional status as measured by improved treadmill/exercise test or increased walking time on six-minute walk test.
Three high-quality studies (n=97) demonstrated that compared with control groups spinal cord simulation improved quality of life (QoL) as measured by a variety of QoL questionnaires (such as Seattle Angina Questionnaire and EuroQol).
One medium- and one high-quality study (n=161) indicated that when spinal cord simulation was compared with CABG, spinal cord simulation had fewer deaths than CABG. When spinal cord simulation was compared to an external control group, there was no difference in mortality.
Two medium- and four high-quality studies (n=282) demonstrated low complication rates. The most common adverse event associated with spinal cord simulation was electrode dislocation, which occurred with lesser frequency in newer studies than in older studies.
Spinal cord simulation versus PMR:
One high quality study indicated that compared with PMR, spinal cord simulation had significantly longer time to angina after three months treatment and a greater reduction in angina pain. Functional status, as measured by six-minute walk test, was not significantly improved with spinal cord simulation.
Spinal cord simulation versus CABG:
One high-quality study indicated that compared with CABG, spinal cord simulation had lower morbidity and mortality rates. Angina symptoms, as measured by angina attacks and nitro consumption, were similar between groups.