Relation between Coronary Sinus O2 Saturation and Response to Cardiac Resynchronization Therapy in Patients with Severe Heart Failure

Backgrounds and Congestive Heart Failure (CHF) is a prevalent disease and has a great economic impact on health systems. Cardiac Resynchronization Therapy (CRT)، which synchronize biventricular contraction، is one of the most important therapies in these patients. Despite the exact selection of patients about 30% of patients do not respond to CRT. The aim of this study was to evaluate the O2 saturation and the pressure level of right side of heart and Coronary Sinus (CS) vein to predict the response to CRT. In this descriptive study، 30 patients were candidate for implantation of CRT echocardiography. The 6 Minute Walk Test (6MW)، right side and CS O2 saturation and pressure study was done before implantation. Echocardiography and 6MW repeated 6 months later. Based on response to the CRT، patients were divided into two groups: “responder and non-responder”. Date were compared between groups. O2 saturation was significantly lower in responders than non-responders. In non-responder patients the Right Ventricular (RV) and Pulmonary Artery (PA) Pressure was significantly higher than responders. Desaturation of CS blood flow in responders was probably due to higher levels of viable tissue which involve in contraction. Increase in right side and PA pressure in non-responders might be due to severity of heart failure which made CRT not effective in these patients. Evaluation of O2 saturation of CS blood flow، RV and PA pressure can use as an index in predicting the response to CRT and can help as additional indices in selection of patients with borderline indications for implanting CRT.