Feasibility and Efficacy of Coronary Sinus Narrowing in Patients With Coronary Microvascular Dysfunction

Inclusion criteria

• Age >18
• Able to provide written informed consent and willing to participate in all required study follow-up assessments
• Symptomatic CAD with refractory angina defined as CCS class II to IV, despite optimal tolerated medical therapy
• Abnormal coronary microvascular function indices: CFR≤2.5 and/or IMR≥25

Exclusion criteria

• Recent (within 3 months) acute coronary syndrome
• Patients with prior coronary artery bypass surgery
• Unstable angina (recent onset angina, crescendo angina, or rest angina with ECG changes) during the last 30 days
• Subjects in cardiogenic shock (systolic pressure < 80mm/Hg, on vasopressors or intraaortic counter pulsation) at the time of consenting. Subjects who recover from cardiogenic shock by the time of consenting are eligible.
• Obstructive CAD on coronary angiography (>70% stenosis or 50-70% stenosis with iFR<0.89 or FFR<0.8 in epicardial artery)
• Inability to perform invasive coronary flow evaluation and/or measure CFR and IMR in the LAD
• Severe valvular heart disease
• LVEF<30%
• Decompensated congestive heart failure (CHF) or hospitalization due to CHF during the last 3 months
• Patient with a pacemaker electrode in the CS
• Mean right atrial pressure >15 mmHg
• Anomalous or abnormal CS anatomy (e.g., tortuosity, aberrant branch, persistent left superior vena cava (SVC) as demonstrated on angiogram
• CS diameter at the site of planned implantation greater than 13mm or less than 9.5 mm as measured by angiogram
• Severe chronic obstructive pulmonary disease (COPD) indicated by a forced expiratory volume in one second that is less than 55 percent of the predicted value
• Tricuspid valve replacement or repair (tissue or mechanical)
• Chronic renal failure (serum creatinine >2mg/dL), and or on chronic hemodialysis
• Moribund, or with comorbidities limiting life expectancy to less than one year
• Known severe reaction to required procedural medication
• Known allergy to stainless steel or nickel
• Magnetic Resonance Imaging (MRI) within 8 weeks of Reducer implantation
• Participation in another ongoing investigational trial
• Additional factors deemed unsuitable for trial enrollment per discretion of principal investigator
• Inmates