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Coronary sinus Reducer (CSR) is an hourglass-shaped device that creates an artificial stenosis in the coronary sinus. Previous studies with this device have shown an improvement in angina complaints, but these results have not been repeated. Although the mechanism of action of this treatment is not yet fully known, it is thought to promote an upward pressure gradient increase, leading to a redistribution of blood flow from the less ischemic epicardium to the ischemic endocardium.

The purpose of the ORBITA-COSMIC study was to compare the effects of the CSR device with placebo on myocardial perfusion, exercise duration, and symptoms detected via cardiac MRI in patients with refractory angina and ischemia.

This study was designed as randomised, double-blind, placebo-controlled. It was conducted in England between May 2021 and June 2023 and included 51 patients suffering from symptomatic angina and ischemia. These patients were selected from patients with stable coronary artery disease (CAD) who were not suitable for percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG). After the patients were included in the study, angina and quality of life questionnaires, treadmill tests and cardiac MRI imaging were performed. Then, patients recorded their symptoms daily in the “Orbita” application. After 2 weeks of follow-up, 24 patients were randomized to the CSR group and 26 patients to the placebo group, and 1 patient was excluded from the study because the device placement procedure was unsuccessful. After 6 months of follow-up, cardiac MRI and exercise tests were repeated. The primary endpoint of the study was stress myocardial blood flow on cardiac MRI. Secondary endpoints were angina frequency, quality of life, and treadmill exercise duration.

The average age of the 51 patients included in the study is 67 years old. 44 of the patients had a history of CABG (86%) and 28 of them had a history of PCI (55%). Results showed that CSR did not significantly improve stress myocardial blood flow in ischemic segments (95% credible interval, 0.09-0.20; probability of benefit=78.8%). However, this method has been shown to improve subendocardial perfusion. Additionally, the findings of the study showed that the frequency of angina decreased and the quality of life due to heart disease increased (odds ratio, 1.4; probability of benefit=99.4%). It was reported that in most patients implanted with the device, angina symptoms did not disappear completely, but there was a decrease in the number of daily pain attacks and the number of days they experienced pain. Positive effects on angina began at 10 weeks post-implantation and continued for up to six months. There was no difference in treadmill exercise duration at follow-up. The CSR device was found to be generally safe. Blood clots occurred in two patients in the CSR group, but no myocardial infarction or death occurred.

According to ORBITA-COSMIC results, the CSR device can lead to a significant reduction in the number of angina attacks in patients with chronic chest pain, but its superiority over placebo in terms of improving myocardial blood flow has not been demonstrated.

With this study, it is thought that CSR may be a new treatment option in patients with refractory angina that cannot be controlled with medications or interventional treatment. What patients want to know in this patient group is whether the device will help reduce their complaints and help them feel better. With the results of this study, patients can be given good news that their symptoms will improve. However, more research is needed to understand the mechanism of the CSR device. It also needs to be determined whether this device will be more useful for certain subgroups. Since the sample size in this study was very low, it would be more accurate to consider these results as a preliminary preparation for future studies. Larger studies are needed to confirm the benefits of the device.