Coronary Sinus Reducer in Coronary Microvascular Disease

Inclusion criteria

• Coronary microvascular dysfunction in the left anterior descending coronary artery (LAD) as expressed by abnormal absolute coronary flow reserve (CFR<2.5) confirmed during the index study procedure using the continuous thermodilution technique and saline-induced coronary hyperaemia.
• Angina - Canadian Cardiovascular Society Class II-IV on at least two anti-anginals or maximally tolerated medical therapy if less than two.
• 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.
• Presence of hemodynamically significant epicardial stenoses based on both non- hyperaemic pressure ratio (NHPR; iFR≤0.89, or RFR≤0.89, or dFR/dPR≤0.89) or fractional flow reserve (FFR≤0.80) assessments.
• Prior positive acetylcholine provocation test with respect to epicardial vasospasm following the COVADIS criteria.
• 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 <35%).
• 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.
• 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.
• Known inability to tolerate contrast medium.
• Life expectancy <1 year.