A Randomised Controlled Trial of the Effect of Remote Ischaemic Conditioning on Coronary Endothelial Function in Patients with Angina.

Intermittent arm cuff inflation reduces the extent of heart muscle injury at the time of cardiovascular injury. The intervention is known as remote ischaemic conditioning (RIC) however the mechanisms by which RIC acts are incompletely understood. One mechanism that might explain the benefits of RIC is an improvement in coronary artery function which in turn might help improve blood flow to heart muscle.

The primary aim is to determine whether intermittent inflation of a blood pressure cuff for 5 min periods at 200 mmHg on 4 occasions separated by 5 minute intervals can improve coronary vascular function compared to cuff placement with no cuff inflation. A secondary aim is to determine whether or not RIC alters the circulating concentrations of small molecules and hormones in systemic blood that regulate coronary endothelial function.

The investigators will perform a randomised controlled trial of RIC in a minimum of 60 patients with known or suspected angina and in whom coronary angiography with angioplasty would be considered. A screening log will be prospectively recorded. In order to be enrolled prior knowledge of the coronary anatomy and disease is necessary, and this information can be obtained by screening referrals for invasive angiography following non-invasive CT coronary angiography, or staged invasive management when angioplasty is intended following initial invasive angiography.

The protocol had initially involved two coronary angiograms with coronary reactivity testing on the same day, with the first angiogram taking place before the RIC-COR intervention and the second angiogram taking place immediately afterwards. However, after enrolling 10 participants it was evident that the total procedure time and hospital stay was unduly long and impractical. Therefore, following consultation with the trial biostatistician, funder and ethics committee, the protocol was amended and the initial angiogram was removed (May 2012). There were no other changes to the study design. Following a change in service arrangements for elective referrals for coronary angioplasty in our hospital, and constraints around staff illness and availability, recruitment was temporarily suspended on logistical grounds (September 2013 to November 2014).

Following informed consent before the invasive procedure, the patient will be randomly assigned to the intervention group (cuff inflation protocol) or the control group (cuff placement, no inflation; sham protocol). The clinical team will be blind to treatment group assignment.