The enduring legacy of sham-controlled trials of internal mammary artery ligation.

In 1959 and 1960 the results of two randomized controlled trials demonstrated that bilateral internal mammary artery ligation was no better than a sham intervention in the treatment of angina. These landmark trials were the first to use blinded placebo controls to evaluate invasive procedures. Revisiting the story of internal mammary artery ligation offers valuable insights into the ethics of sham-controlled trials and the implications of the placebo effect for thinking about risk-benefit assessment of sham procedures.