Abstract
Abstract Background The benefits of invasive therapies for chronic stable angina are in large part supported by open label studies comparing invasive procedures to medical therapy alone. Placebo effects are frequently unaccounted for as control arms rarely receive placebo (sham) interventions. This review pools studies comparing invasive therapies for chronic stable angina to placebo interventions and aims to measure the true effects of different invasive interventions. Methods We performed a systematic review and meta-analysis of double blinded randomized placebo-controlled trials of invasive therapies for the management of chronic stable angina. The outcomes of interest were change in exercise tolerance time, change in Canadian cardiovascular society angina grade and rate of post-procedural complications including myocardial infarction and all-cause mortality. Results Six randomized placebo-controlled trials were included, with a total of 742 participants. Median follow-up ranged from 6 weeks to 16 months. Contrary to data reported in individual studies, pooled analysis favored invasive therapies over placebo procedures: exercise tolerance time was higher (standard mean difference (SMD) 35.2 seconds [4.4- 66.0]), angina scores were more likely to improve by ≥1 class (Odds Ratio (OR) 2.16 [1.05- 4.46]) and by ≥2 classes (OR 1.76 [1.13- 2.74]). There was no difference in post-procedural myocardial infarction (incidence rate ratio (IRR) 2.91 [0.61–13.93]) and all-cause mortality (IRR 0.39 [0.35–4.27]). Conclusions This meta-analysis of placebo-controlled trials for chronic stable angina found a beneficial effect from invasive therapies. This favorable effect has not been seen in individual studies. Our findings suggest that sample sizes should be adjusted upwards in placebo-controlled studies to detect true treatment effects independent of the placebo effect. Funding Acknowledgement Type of funding source: None
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