Real-Time MR Imaging-guided Laser Atrial Septal Puncture in Swine

Purpose The authors performed this study to report their initial preclinical experience with real-time magnetic resonance (MR) imaging–guided atrial septal puncture by using a MR imaging–conspicuous blunt laser catheter that perforates only when energized. Materials and Methods The authors customized a 0.9-mm clinical excimer laser catheter with a receiver coil to impart MR imaging visibility at 1.5 T. Seven swine underwent laser transseptal puncture under real-time MR imaging. MR imaging signal-to-noise ratio profiles of the device were obtained in vitro. Tissue traversal force was tested with a calibrated meter. Position was corroborated with pressure measurements, oximetry, angiography, and necropsy. Intentional non-target perforation simulated serious complication. Results Embedded MR imaging antennae accurately reflected the position of the laser catheter tip and profile in vitro and in vivo. Despite having an increased profile from the microcoil, the 0.9-mm laser catheter traversed in vitro targets with similar force (0.22 N ± 0.03) compared with the unmodified laser. Laser puncture of the atrial septum was successful and accurate in all animals. The laser was activated an average of 3.8 seconds ± 0.4 before traversal. There were no sequelae after 6 hours of observation. Necropsy revealed 0.9-mm holes in the fossa ovalis in all animals. Intentional perforation of the aorta and atrial free wall was evident immediately. Conclusions MR imaging–guided laser puncture of the interatrial septum is feasible in swine and offers controlled delivery of perforation energy by using an otherwise blunt catheter. Instantaneous soft tissue imaging provides immediate feedback on safety.