ORBITA trial on heart stents for stable angina indicates placebo effect potential

A new study conducted by researchers at the Imperial College London suggests that the placebo effect experienced by patients who receive coronary artery stents might be larger than expected, even though stents themselves are life-saving.

This ORBITA (Objective Randomized Blinded Investigation with optimal medical Therapy of Angioplasty in stable angina) trial is the first of its kind to compare stenting for stable angina with a simulated procedure in which implantation of a stent was not carried out.

The results of the trial published in The Lancet and presented at the Transcatheter Cardiovascular Therapeutics 2017 conference in Denver, Colorado showed that the treatment lacked any added noteworthy benefits on the symptoms or quality of life of patients.

Dr Rasha Al-Lamee, lead author of the study from the National Heart & Lung Institute at Imperial College London, commented: "The most important reason we give patients a stent is to unblock an artery when they are having a heart attack. However, we also place stents into patients who are getting pain only on exertion caused by narrowed, but not blocked arteries. It's this second group that we studied."

It was surprising to note that the stent —even if it enhanced blood supply—had not provided greater relief from symptoms than those provided by drug treatment, added Dr. Al-Lamee.

However, the findings do not indicate that patients should not undergo stenting for stable angina; in controlling symptoms, some patients might opt for an invasive procedure over taking long-term medication.

Stable angina is a commonly occurring condition in adults, where the affected person feels chest pain because of overexertion caused due to the restriction of blood flow toward the heart. This is caused due to the hardening and narrowing of the arteries owing to the presence of fatty plaques in their walls, leading to decreased arterial flexibility.

The condition could be managed with drugs like nitro-glycerine or beta-blockers.  A few may even undergo an invasive procedure called Percutaneous Coronary Intervention (PCI) or angioplasty with stent.

Across the globe, nearly 500,000 patients are estimated to undergo PCI for stable angina every year. This procedure is expected to bring considerable release from symptoms for such patients.  However, since the introduction of the procedure, it has remained unclear if the relief from symptoms was due to a placebo effect or the treatment alone.

The trial enrolled 200 participants with stable angina, who possessed narrowing in one single coronary vessel, via hospitals in London and in the south of England. Initially, they were provided with medications that are used to treat angina and the dosage was increased to the maximum over a six-week period.

Then, the participants were randomly chosen to either receive a stent or a placebo procedure, where they received no stent, but an angiogram procedure. Half of the participants received the placebo, while the other half received the stent; both the patients and their doctors were unaware of the procedure received by the patients for the following six weeks.  

To evaluate the patients’ speed on a treadmill, they had exercise tests prior to and after the six-week procedure, during which their lung and heart functions were calculated.  The difference in the amount of time the patients could exercise after the procedure was considered as the key outcome.

The findings indicated that for patients who had PCI, the median increase in overall exercise time was 28·4 sec, whereas in the placebo group, it was 11·8 sec.

Statistically, the difference between the two groups does not seem significant. The researchers were unable to confirm whether the effect was down to the stent, or down to chance. Also, in both the groups, they could not record any noteworthy differences in patient-reported improvement of symptoms.

However, the study confirmed that the stenting procedure relieved narrowing in the coronary artery and enriched the supply of blood to the heart. This confused the researchers as they thought that the exercising capacity and symptoms would be enhanced when the artery is opened, and the blood supply is enriched.

The high dosage of medication provided to the participants prior to the procedure, may not be a realistic treatment prior to angioplasty with a stent, and the nature of the study group containing only patients affected in single-vessel are possible study limitations the researchers explained.

The researchers further aim to investigate deeper in order to detect if there are patient-subgroups whose angina might be enhanced more after stenting.