The MiCardia DYANA annuloplasty system (MiCardia Corp, Irvine, Calif) is a nitinol-based dynamic complete ring that allows modification of the septal-lateral diameter under transesophageal echocardiography guidance in the loaded beating heart after mitral valve repair. Shape alteration is induced by radiofrequency via detachable activation wires. This multicenter study reports the first human experience with this device.Patients (n = 35, 67 ± 8 years) with degenerative (n = 29), functional/ischemic (n = 5), or rheumatic (n = 1) mitral regurgitation underwent mitral valve repair using the new device. We analyzed the occurrence of death, endocarditis, ring dehiscence, systolic anterior motion, thromboembolism, pulmonary edema, heart block, ventricular arrhythmia, hemolysis, or myocardial infarction at 30 days (primary end point) and 6 months (secondary end point) postprocedure.All patients exhibited mitral regurgitation of 2 or less early postoperatively and at 6 months follow-up. In 29 patients, the initial mitral valve repair result was satisfactory and no ring activation was required. In 6 patients, the nitinol-based ring was deformed intraoperatively postrepair with further improvement of mitral regurgitation in all cases (preactivation: 0.9 ± 0.2, postactivation: 0.2 ± 0.3; P = .001). One death (2.9%, multisystem organ failure, non-device related), 2 ventricular arrhythmias (5.7%), and 1 heart block (2.9%) occurred, all in the first 30 days after surgery. No additional major adverse clinical events occurred later than 1 month postprocedure (total observed major adverse clinical event rate 11.5%).The implantation of the new dynamic annuloplasty ring allows for safe mitral valve repair. The option of postrepair modification of the septal-lateral diameter by radiofrequency may further optimize repair results.