Symptomatic angina in patients with ischaemia and non-obstructed coronary arteries (INOCA) is common and associated with increased morbidity and adverse outcomes. Myocardial ischaemia often arises from coronary microvascular dysfunction (CMD). Current treatments are limited, and novel evidence-based therapies are needed to address this large unmet clinical need. The Coronary Sinus Reducer (CS Reducer) is a new treatment for refractory angina, which creates a focal narrowing in the coronary sinus that increases back pressure and redistributes blood into ischaemic myocardium at the level of the microcirculation. However the precise mechanism remains unknown. This study will be a randomised double-blinded sham-controlled pilot study (REMEDY-PILOT) to confirm acceptability of CS Reducer implantation, demonstrate feasibility to recruit and quantify its effect on myocardial perfusion. A nested mechanistic substudy within REMEDY-PILOT will test the hypothesis that CS Reducer implantation alters measures of invasive coronary microcirculatory physiology as the mechanistic basis for observed changes in quantitative CMR stress perfusion, symptoms and quality of life.
To demonstrate the feasibility and efficacy of the CS Reducer for the treatment of patients with ischaemia and non-obstructed coronary arteries (INOCA) and coronary microvascular dysfunction (CMD) and through a nested mechanistic substudy investigate the physiological responses in the coronary microcirculation responsible for changes in myocardial perfusion.