Objective: The purpose of this study was to evaluate the implantability of a novel epicardial mitral annuloplasty device and its ability to reduce the septal-lateral (S-L) dimension of the mitral annulus. Methods: The devices were implanted on the beating heart in 2 healthy dogs (the 24-mm long device in dog A and the 27-mm and 24-mm standard devices in dog B) by sliding the anterior arm onto the floor of the transverse sinus and positioning the posterior arm just apical to the atrioventricular groove on the left ventricular posterolateral wall. The devices were secured with titanium helical tacks driven through the device into the ventricular wall. Twodimensional epicardial echocardiograms were performed before and after device implantation to evaluate the degree of mitral regurgitation (MR) and the S-L dimension. Results: Device implantation was uneventful, taking only ~30 seconds to deploy. MR (1) in both dogs at baseline was reduced to zero after implant. The reductions in S-L dimension in systole for the 24-mm device were 7.5% in dog A and 30.5% in dog B. For the 27-mm device in dog B, S-L reduction in systole was 29.9%. The leaflet coaptation length was increased in both cases. Conclusions: The new device was effective in reducing S-L dimension and 1 MR without requiring the use of cardiopulmonary bypass. We are currently evaluating this device for the treatment of MR in a rapid-pacing canine heart failure model.