Coronary Sinus Reducer Improves Angina, Quality of Life, and Coronary Flow Reserve in Microvascular Dysfunction

Background: Coronary microvascular dysfunction (CMD) is a common cause of angina with no obstructive coronary artery disease (ANOCA), and effective treatment options are limited.

Objectives: This study aims to assess the safety and efficacy of the coronary sinus (CS) Reducer (Neovasc, Inc/Shockwave Medical) for treatment of angina in patients with CMD.

Methods: This Phase II trial enrolled 30 patients with ANOCA, invasively diagnosed CMD, and Canadian Cardiovascular Society (CCS) class 3 to 4 angina despite medical therapy. CMD was defined by coronary flow reserve (CFR) ≤2.5 and/or ≤50% increase in coronary blood flow (CBF) in response to intracoronary infusion of acetylcholine. Invasive coronary microvascular function testing was performed before and at 120 days postimplantation. The primary endpoint was change in microvascular function at 120 days. Secondary endpoints were changes in CCS angina class and Seattle Angina Questionnaire (SAQ) scores.

Results: Mean age was 54.8 ± 11.0 years; 67% (20/30) were women. In patients with low baseline CFR (endothelium-independent CMD), CFR increased significantly from 2.1 (1.95-2.30) to 2.7 (2.45-2.95) (n = 19; P = 0.0011). Patients with abnormal CBF response to acetylcholine at baseline (endothelium-dependent CMD) had an increase in CBF response to acetylcholine: -11.0% (-20.15% to 5.85%) to 11.5% (-4.82% to 39.29%) (n = 11; P = 0.042). There was a significant improvement in CCS angina class from 4.0 (3.25-4.0) to 2.0 (2.0-3.0) (P < 0.001) and increase in each domain of the SAQ questionnaire (P < 0.006 for all).

Conclusions: This study demonstrates that the CS Reducer is associated with significant improvement in angina, quality of life, and coronary microvascular function in patients with CMD and may emerge as a novel therapy for patients with ANOCA.