Randomized trials of invasive cardiovascular interventions that include a placebo control: a systematic review and meta-analysis

Aims The difference in the benefit of invasive cardiovascular interventions compared with placebo controls has not been analysed systematically. Methods and results MEDLINE and Web of Science were searched through 29 March 2020. Randomized, placebo-controlled trials of invasive cardiovascular interventions (including catheter-based interventions and pacemaker-like devices) investigating predefined primary outcomes were included. Standardized mean differences (SMD) and odds ratios were calculated for continuous and dichotomous outcomes, respectively. Meta-regression analyses were performed to assess whether estimates of treatment effects were associated with methodological characteristics of trials. Thirty trials, including 4102 patients, were analysed. The overall risk of bias was judged to be low in only 43% of the trials. Ten trials (33%) demonstrated statistically significant superiority of invasive interventions over placebo controls for the respective predefined primary outcomes. In almost half of the 16 trials investigating continuous predefined primary outcomes, the SMD between the active and placebo procedure indicated a small (n = 4) to moderate (n = 3) treatment effect of active treatment over placebo. In contrast, one trial indicated a small treatment effect in favour of the placebo procedure. In the remaining trials, there was no relevant treatment effect of active treatment over placebo. In trials with a protocol-mandated stable and symmetrical use of co-interventions, the superiority of active procedures vs. invasive placebo procedures was significantly larger as compared with trials with frequent or unbalanced changes in co-interventions (P for interaction 0.027). Conclusions The additional treatment effect of invasive cardiovascular interventions compared with placebo controls was small in most trials.