Chronic angina pectoris refractory to medical and revascularization therapies is a disabling medical condition and a major public health problem. Patients with refractory angina have limited treatment options. One proposed therapy modality is transcatheter implantation of a reduction stent in the coronary sinus. Coronary sinus reduction stents have been shown to reduce angina burden considerably and to improve quality of life. The reduction stent is assumed to increase myocardial perfusion and reduce myocardial ischemia, but the mechanism of action is poorly understood.

The aim of this project is to assess the myocardial ischemia burden in patients with refractory angina who are undergoing a transcatheter coronary sinus reducer procedure. This is a clinical non-randomized self-controlled cohort study with blinded outcome adjudication for changes in myocardial perfusion. Patients with refractory angina will be systematically examined before implantation of the coronary sinus reduction stent and after 6 months. The primary outcome, changes in myocardial perfusion on the gold standard 15O-H2O PET/CT will be evaluated on blinded perfusion scans where the stent is invisible. To provide context to the findings, we will also evaluate whether changes in myocardial ischemia are associated with less angina and better cardiac function parameters. Effects of stent implantation on angina symptoms and quality of life could be affected by a placebo effect.

Treatment options for patients with refractory angina is needed, and results from the present study will explore if coronary sinus reduction stents are improving myocardial ischemia in this patient group. Signs of improved objective perfusion will inspire confidence in the method.

Inclusion Criteria:

• Coronary artery disease and refractory angina
• Clinical indication for coronary sinus reduction stent implantation
• Written informed consent
• Anticipated compliance with protocol

Exclusion Criteria:

• Ineligibility for coronary sinus reduction stent implantation
• Lack of informed consent
• Not expected to comply with protocol

Patients with coronary artery disease and refractory angina who are under clinical care are informed and screened for participation if consent is provided.

We aim to share data upon request from other academic investigators, but await EC approval