Background: 
Chronic coronary syndrome is a major healthcare problem affecting millions of patients worldwide. Refractory angina (RA) majorly impairs quality of life. In some cases, complete coronary revascularization (CR) can neither be achieved by surgery nor by percutaneous coronary intervention (PCI). The coronary sinus reducer is a non-pharmacological solution for symptom relief in those patients. It is an hourglass-shaped device which is advanced to the coronary sinus. By that, venous pressure in the heart is increased which results in a dilatation of arterioles and reduced vascular resistance in the sub-endocardium. Consequently, the coronary blood flow is redistributed leading to reduction of ischemia and symptoms. We aimed to assess the safety and in-hospital outcome of the CSR in a real-world case series of patients with RA.

Methods and results:
13 Patients (40% female, mean age 72±7 years) underwent CSR implantation at our institution. All the patients were on nitrates, betablockers and statins, 9 patients additionally received ranolazine and 6 patients ivabradine.  Previous therapeutic attempts for CCR were performed with bypass surgery in 60 % and PCI in 85 % of the patients. 40 % had previous myocardial infarction and 85 % suffered from diabetes mellitus. All patients had severe RA despite medical treatment and without any options for conventional revascularization but objective evidence of myocardial ischemia assessed by single-photon emission computed tomography (SPECT). We assessed safety, which was defined as the absence of device-related adverse events, and acute procedural success.  Primary successful CSR Implantation was in 93 % of patients presenting with RA who were not candidates for further revascularization. There were no procedure-related complications and MACCE events. In-hospital mortality was 0 %.

Conclusions:
In this real-world, single-center experience, implantation of the CSR appeared simple and safe option without any procedure related complication and MACC during the hospital stay for reducing symptoms in patients with RA who were not candidates for further revascularization.