Coronary Sinus Reducer for Refractory Angina: Notes from the REDUCER-I Study

Refractory angina is defined as the presence of ischemic symptoms that cannot be controlled through optimal medical therapy (OMT) or interventional treatment. Patients who suffer from it often have significantly impaired quality of life (QoL) and impose high costs on healthcare systems. Therefore, the main objective of treatment in such cases is to reduce symptoms, improve QoL, and minimize the need for recurrent hospitalization.

The Reducer (Shockwave Medical Inc.) is a device designed to decrease the diameter of the coronary sinus (CS), creating a focal narrowing that promotes redistribution of myocardial blood flow to the ischemic subendocardium. Previous studies, such as COSIRA and ORBITA-COSMIC, have shown that this device can significantly reduce episodes of angina.

The REDUCER-I study is a non-randomized observational study that assessed the effectiveness and safety of the device in a large and complex cohort of patients with non-revascularizable refractory angina in 9 European sites. Recently, researchers presented an interim analysis with the results at 3 years.

The primary effectiveness endpoint was the percentage of patients who experienced improvement in their functional angina class (according to the Canadian Cardiovascular Society) at 6 months compared to baseline. The primary safety endpoint included the incidence of severe periprocedural adverse events and major adverse cardiovascular events (MACE) within 30 days from implantation.

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A total of 382 patients were included and 97.1% of them received the device (95.3% on the first attempt). The average age was 68.8 years, and 78% of subjects were men. Additionally, 73.6% had a history of myocardial revascularization surgery (MRS), 72.2% had CCS class III-IV angina, and 66.1% were on treatment with three or more anti-anginal medications.

At baseline, patients had an average CCS score of 2.8±0.6, which improved to 1.8±0.8 at 6 months (-0.9±0.8; P <0.0001). Among patients with disabling angina (CCS III-IV, 72%), only 18.2% remained in this category at 6 months, while 69.8% improved by at least one functional class and 24.1% improved by two or more classes.

In terms of safety, the incidence of MACE at 30 days was 1.6% (95% confidence interval [CI]: 0.7%-3.6%). Six cases of acute myocardial infarction (AMI) were reported within the first 30 days, but none were related to the procedure. Furthermore, the rate of severe adverse events was 1.1%, including one case of AMI, one pericardial effusion event, and three cases of device migration.

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Quality of life (QoL) scores measured by the SAQ questionnaire and angina frequency showed significant improvements compared to baseline (P <0.0001). In the 3-year interim analysis, patients in follow-up maintained a sustained reduction in CCS functional class, with fewer than 20% remaining in CCS III-IV (P <0.0001).

Conclusions

Reducer implantation in this complex population resulted in a significant reduction in CCS functional class in nearly 70% of patients, with benefits sustained at 6 months and at 3 years. Additionally, the procedure proved to be safe, with few adverse events reported.

Original Title: Coronary Sinus Narrowing for Treating Refractory Angina. REDUCER-I Multicenter “Real-World” Observational Study Primary Endpoint Analysis

Reference: Verheye S, van de Hoef TP, de Silva R, van Kuijk JP, Byrne J, Montorfano M, Buschmann E, Dupont M, West NEJ, Banai S; REDUCER-I Study Investigators. Coronary Sinus Narrowing for Treating Refractory Angina: REDUCER-I Multicenter “Real-World” Observational Study Primary Endpoint Analysis. JACC Cardiovasc Interv. 2024 Dec 23;17(24):2908-2918. doi: 10.1016/j.jcin.2024.08.047. Epub 2024 Nov 6. PMID: 39520437.