Atrial Septal Puncture
Interatrial septa isolated from 36 porcine hearts were immersed in a room temperature bath of 0.9% sodium chloride solution and positioned on a cork sample holder to normalize force applied during puncture (Figure 2A). RF energy was delivered using the RF wire and electrified guidewires under each power setting. Additional energy applications were delivered until the tip of the wire perforated the septum, or up to a maximum of 8 attempts. Failure to puncture was defined as the inability to perforate the septum after 8 RF applications. To model a range of conditions in clinical practice, multiple distances from the distal wire to the dilator tip were tested; 1mm (i.e. underexposure of wire tip), 3mm (i.e. ideal wire tip exposure) and 5mm (i.e. over-exposure of wire). The number of RF applications required to perforate the septum was recorded for each treatment condition. Each treatment condition was repeated at least six times. Inspection of puncture sites was performed immediately post-puncture under 30-50X magnification using an optical microscope (VHX-5000, Keyence, Osaka, Japan) to confirm TSP success and qualitatively assess the defect site.