Arm 2 (control): Implantation procedure with no device implanted clinical trials

Efficacy of the COronary SInus Reducer in Patients With Refractory Angina II

This study looks at a new device for people with severe chest pain (refractory angina) caused by heart disease, who can't have standard treatments. It aims to see if the device, called a 'Reducer', can safely and effectively reduce their pain.