Retrieval of a Micra transcatheter pacing system in a heart with a preexisting lead

We report the case of a 74-year-old man with a previously implanted pacemaker lead. He had undergone Medtronic™ Micra Transcatheter Pacing System (TPS, Medtronic plc, MN, USA) implantation because of lead fracture. We implanted a new TPS and retrieved the dislodged one. We used a multiple-loop snare (EN snare®) and an 8.5F steerable sheath (Agilis NXT; St. Jude Medical, St Paul, MN, USA). The TPS was obstructed by the chordae tendineae of the tricuspid valve and the pacemaker lead. We pushed the TPS to the apex site; this enabled us to move the TPS away from the chordae tendineae and pacemaker lead. The TPS body was caught in the inferior vena cava and was successfully retrieved. To our knowledge, this is the first case reporting TPS retrieval in a heart with preexisting lead. Keywords: Dislodgement, Transcatheter pacing system, TPS retrieva

Radiofrequency ablation of ventricular premature contraction originating from a native coronary cusp after transcatheter aortic valve replacement

We describe a case of radiofrequency ablation of ventricular premature contraction (VPC) originating from the left ventricular outflow tract after transcatheter aortic valve replacement. The VPC origin was the native aortic valve annulus between the left and right coronary cusps. Radiofrequency ablation was successfully performed by manipulating the ablation catheter from the gap between the sinotubular junction and implanted valve. Keywords: Radiofrequency ablation, Transcatheter aortic valve replacement, Ventricular premature contraction, Ventricular arrhythmi

Cortical Polarity of the RING Protein PAR-2 Is Maintained by Exchange Rate Kinetics at the Cortical-Cytoplasmic Boundary

SummaryCell polarity arises through the spatial segregation of polarity regulators. PAR proteins are polarity regulators that localize asymmetrically to two opposing cortical domains. However, it is unclear how the spatially segregated PAR proteins interact to maintain their mutually exclusive partitioning. Here, single-molecule detection analysis in Caenorhabditis elegans embryos reveals that cortical PAR-2 diffuses only short distances, and, as a result, most PAR-2 molecules associate and dissociate from the cortex without crossing into the opposing domain. Our results show that cortical PAR-2 asymmetry is maintained by the local exchange reactions that occur at the cortical-cytoplasmic boundary. Additionally, we demonstrate that local exchange reactions are sufficient to maintain cortical asymmetry in a parameter-free mathematical model. These findings suggest that anterior and posterior PAR proteins primarily interact through the cytoplasmic pool and not via cortical diffusion