Refractory angina due to advanced obstructive coronary artery disease (CAD) remains a major clinical problem with limited evidence-based treatment options. The coronary sinus reducer (CSR) is an hourglass-shaped stainless-steel mesh device designed to create a controlled narrowing of the coronary sinus (CS). By increasing CS pressure, CSR implantation may improve myocardial perfusion and reduce anginal symptoms, although the physiological mechanisms underlying this effect remain incompletely understood.

REDUCE-ANGINA is a prospective observational study investigating the hemodynamic effects of CSR implantation in 25 patients with refractory angina and advanced CAD. The study evaluates the interaction between coronary sinus hemodynamics and coronary arterial blood flow before and after CSR implantation. The main study endpoints include changes in coronary sinus pressure, coronary flow reserve, microvascular resistance reserve, and absolute microvascular resistance from baseline to 6 months, measured using continuous flow thermodilution during saline-induced coronary hyperemia.

Inclusion Criteria:

• Angina - Canadian Cardiovascular Society Class II-IV on at least two anti-anginals or maximally tolerated medical therapy if less than two.Hemodynamically significant epicardial coronary artery disease in the LAD, defined as an FFR≤0.80 and/or NHPR≤0.89.
• No conventional revascularization options or considered unsuitable as determined by the local heart team.
• Anatomically suitable for instrumentation of the left anterior descending coronary artery with a coronary pressure wire and infusion microcatheter.
• Patient understands the nature of the procedure and provides written informed consent for the study prior to enrolment.

Exclusion Criteria:

• Age < 18 years.
• Absence of symptoms reported on the ORBITA-app during the 2-week screening period.
• Mean right atrial pressure ≥15 mmHg
• Severe pulmonary hypertension.
• Coronary sinus anatomy not suitable for CSR implantation.
• Pregnancy or planned pregnancy within the next 12 months.
• Recent acute coronary syndrome (within 3 months).
• Recent revascularization with PCI (within 6 months).
• Severe arrhythmias, including chronic atrial fibrillation with persistent rapid ventricular response (>100bpm despite medication).
• Indication for cardiac resynchronization therapy.
• Severe left ventricular impairment (left ventricular ejection fraction <30%).
• NYHA class IV or decompensated heart failure or hospitalization due to heart failure within 90 days before the index procedure.
• Recent implantation of a permanent pacemaker or defibrillator lead in the right ventricle or atrium (within 90 days before the index procedure).
• Presence of a pacemaker lead in the coronary sinus.
• Severe valvular heart disease.
• History of tricuspid valve replacement or repair.
• Kidney failure (estimated glomerular filtration rate <30ml/min)
• Contra-indication to short term dual antiplatelet therapy or lifelong aspirin treatment.
• Currently enrolled in another investigational device or drug trial that has not completed the primary endpoint or that clinically interferes with the current study endpoints.
• Unable or unwilling to use the ORBITA app
• Known inability to tolerate contrast medium.
• Life expectancy <1 year.