A system for repairing a heart valve in a beating heart of a patient, comprising: a port adapted to span a wall of the heart of the patient, the port having an opening extending therethrough configured to provide access to the interior of the heart, and a proximally facing surface; a catheter (104; 106) slidably insertable into the opening of the port, the catheter (104; 106) including at least one imaging element and a deployment mechanism and the catheter further having a proximal portion that is raised relative to the outer surface of the catheter, the proximal portion comprising a distally facing surface, and a distal end that forms a first portion of a jaw assembly adapted to grasp target tissue for repair in the heart; a repair cartridge slidably insertable into the catheter (104; 106), the repair cartridge carrying a repair device that can be deployed into the target tissue in conjunction with the deployment mechanism and having a shaft with a tip at a distal end of the shaft that forms a second portion of the jaw assembly, wherein the imaging element is configured to confirm proper capture of the target tissue with the jaw assembly; an elongate removable locking mechanism configured to engage with the catheter (104; 106) longitudinally along a length of an outer circumferential surface of the catheter (104; 106), and thus provide a physical barrier sandwiched between the proximally facing surface of the port and the distally facing surface of the catheter (104; 106) to prevent the catheter (104; 106) from moving distally relative to the port, and furthermore configured to be removable from contact with both the catheter (104; 106) and the port, so that the catheter is free to slide distally relative to the port; and a seal (138; 140) positioned within the opening of the port, the seal (138; 140) adapted to substantially prevent blood from escaping the heart through the port while providing for selective insertion and removal of the catheter (104; 106) and repair cartridge through the port while the heart of the patient is beating. a port adapted to span a wall of the heart of the patient, the port having an opening extending therethrough configured to provide access to the interior of the heart, and a proximally facing surface; a catheter (104; 106) slidably insertable into the opening of the port, the catheter (104; 106) including at least one imaging element and a deployment mechanism and the catheter further having a proximal portion that is raised relative to the outer surface of the catheter, the proximal portion comprising a distally facing surface, and a distal end that forms a first portion of a jaw assembly adapted to grasp target tissue for repair in the heart; a repair cartridge slidably insertable into the catheter (104; 106), the repair cartridge carrying a repair device that can be deployed into the target tissue in conjunction with the deployment mechanism and having a shaft with a tip at a distal end of the shaft that forms a second portion of the jaw assembly, wherein the imaging element is configured to confirm proper capture of the target tissue with the jaw assembly; an elongate removable locking mechanism configured to engage with the catheter (104; 106) longitudinally along a length of an outer circumferential surface of the catheter (104; 106), and thus provide a physical barrier sandwiched between the proximally facing surface of the port and the distally facing surface of the catheter (104; 106) to prevent the catheter (104; 106) from moving distally relative to the port, and furthermore configured to be removable from contact with both the catheter (104; 106) and the port, so that the catheter is free to slide distally relative to the port; and a seal (138; 140) positioned within the opening of the port, the seal (138; 140) adapted to substantially prevent blood from escaping the heart through the port while providing for selective insertion and removal of the catheter (104; 106) and repair cartridge through the port while the heart of the patient is beating.