Coronary sinus Reducer non-responders: insights and perspectives.

AIMS: Coronary sinus (CS) Reducer is currently indicated for the treatment of refractory angina in patients unsuitable for coronary revascularization. A 15-30% of non-responders is a constant across literature. Alternative coronary venous drainage systems may be an important factor in determining if patients "respond" to this intervention. We propose a simple method to indirectly assess the presence of these alternative drainage systems and predict responsiveness to Reducer implantation.

METHODS AND RESULTS: We measure the differential pressure between baseline right atrial pressure and CS systolic pressure during balloon occlusion of the CS. In the majority of patients, most of the left coronary artery venous return is drained by the CS. These patients show a high differential pressure due effective interference of the Reducer with coronary venous return. Narrowing of the CS effectively reduces venous return establishing its anti-ischemic effects, with the most expected benefit from Reducer implantation. Patients with developed accessory venous drainage systems will show low differential pressures due to preserved alternative coronary venous outflow. In these patients, Reducer results in an insufficient pressure gradient across the CS and the anti-ischemic effects and benefits might be minimal.

CONCLUSIONS: We suggest a simple and effective diagnostic peri-procedural method that may provide additional information in predicting responders to Reducer therapy. We also explore CS hemodynamics in the setting of Reducer implantation, trying to give insights on the pathophysiology and biologic effect of this novel treatment. This may help clinicians to better select patients to undergo implantation, avoiding useless procedures and risks.