Mitral regurgitation (MR) is a common valvular heart disease in the elderly population, frequently associated with poor prognosis if not treated. Transcatheter edge-to-edge repair (TEER) has recently emerged as a popular strategy due to minimal invasiveness. What's more, previous studies, such as EVEREST II and COAPT study, have demonstrated its efficacy in high-risk patients with primary or secondary MR. Conventional TEER procedure, however, is performed under combined guidance of both echocardiography and fluoroscopy, which potentially results in high radiation exposure and limits its application. Since 2021 2021, the investigators have changed the procedural methodology by performing TEER under full echocardiographic guidance on accumulated dozens of MR patients successfully. To confirm the efficacy of a fully echo-guided TEER procedure, the investigators conduct the ECHO-CLIP study to compare its outcomes with the conventional TEER procedure, as well as evaluate the outcomes of this novel methodology in special populations with radiation contraindications. ECHO-CLIP study is a prospective, multicenter, open-label, noninferior, randomized controlled trial of TEER by two different methodological strategies in treating severe primary or secondary MR. It is anticipated to enroll a total of 200 patients as well to complete the enrollment before Dec 31, 2025 and the follow-up before Dec 31, 2026. This work will potentially demonstrate the feasibility and efficacy of the fully echo-guided TEER procedure, thereby revolutionizing the TEER methodology and benefiting more patients.