Efficacy of Diltiazem to Improve Coronary Microvascular Dysfunction: A Randomized Clinical Trial [EDIT-CMD] This first performed randomized, placebo-controlled trial in patients with ANOCA showed that 6 weeks of therapy with diltiazem, when compared with placebo, did not substantially improve CVDys, symptoms, or quality of life, but diltiazem therapy did reduce prevalence of epicardial spasm.