Quality of Life Assessment in Trials of Revascularization for Chronic Stable Angina: Insights from ORBITA and the Implications of Blinding

The main aims of therapy in chronic stable angina are to reduce the risk of myocardial infarction and death and improve symptoms and quality of life (QoL). Unblinded trials have shown that revascularization does not reduce the risk of myocardial infarction or death but does appear to improve symptoms. However, symptoms are susceptible to the placebo effect which can bias therapies to appear more effective than they are. To assess the true physical impact of a treatment on symptoms, placebo-controlled trials with patients and medical and research teams blinded to treatment allocation are necessary. Symptoms and QoL can be reported directly by the patient or indirectly by the physician. Patient-reported outcome measures in angina trials can include angina frequency, frequency of nitrate use, exercise capacity, and questionnaires such as the Seattle Angina Questionnaire (SAQ) and the generic EuroQOL-5D-5L (EQ-5D-5L) QoL questionnaire. Physician-assessed outcome measures include Canadian Cardiovascular Society Class. The Objective Randomised Blinded Investigation with Optimal Medical Therapy of Angioplasty in Stable Angina (ORBITA) trial was the first blinded placebo-controlled study investigating the role of percutaneous coronary intervention (PCI) in chronic stable angina. The trial showed a smaller than expected and not statistically significant effect of placebo-controlled PCI on the primary endpoint of change in exercise time at 6 weeks follow-up in single-vessel coronary artery disease. There was also no significant placebo-controlled treatment effect of PCI for the prespecified secondary endpoints of SAQ or EQ-5D-5L, although PCI did result in 20% more patients becoming free from angina than placebo in a non-prespecified secondary analysis. ORBITA has demonstrated the need for symptomatic and QoL effects of PCI to be studied using placebo control. Here, we describe ways of measuring QoL, the impact of the unblinded and blinded trials to date, what we have learned from ORBITA, and what is next for this common and complex condition.