Conduction gaps after pulmonary vein isolation due to high contact force ablation in patients with atrial fibrillation

Background Catheter ablation for atrial fibrillation (AF) with high contact force (CF) has been reported to lead to the gaps after pulmonary vein isolation (PVI), and the appearance of the gaps depends on the site in the left atrium (LA). Purpose The aim of this study is to clarify the relationship between the gaps appearance and high CF. Methods In the clinical study, 74 consecutive patients (39 males, age 71±9, 46 with paroxysmal AF) underwent conventional PVI with a point-by-point radiofrequency (RF) ablation using a CF sensing catheter (TactiCath SETM). RF energy (J), number of RF point, Lesion index (LSI), force-time integral (FTI), average CF (g), and the degree of LA depression with high CF were evaluated. In the experimental study (figure), the relationship between the ablation area and the degree of depression with high CF using bovine left ventricular wall. Results In the clinical study, the gaps were found in 175 of 1182 sites after first path PVI ablation. The CF in the gap sites was higher than without the gap sites in RPV roof, anterior RSPV and anterior RPV carina (18.9±6.8 vs 15.0±5.7g p=0.0262, 26.4±11.6 vs 19.5±6.0g p=0.0029, 22.7±6.4 vs 19.1±5.5g, p=0.0161). Meanwhile, there were no differences in RF energy, number of RF point, LSI, FTI. High CF (≥30g) showed a depression of 3 mm or more in only RPV roof and anterior RPV (figure). In the experimental study, the ablation range narrowed as the indentation deepened with more than 30g CF (r=0.6417, p=0.0625). Conclusion Catheter ablation for AF with high contact force might lead to the gaps in RPV roof and anterior RPV site by the reduction of the ablation area due to depression caused by the pressure. Extension of each contact force Funding Acknowledgement Type of funding source: None

Mechanical nanogap switch for low-power on-board electronics

This paper presents the design fabrication and measurement of a nanogap radio frequency microelectromechanical system (RF MEMS) metal-contact switch. The prosed device generates a relatively high contact force with a low actuation voltage using a dielectric layer between the actuation electrode and the moveable beam. The actuation voltage is decreased with good reliability of the device by scaling down the gap. Beam geometry optimization allowed reaching 126 micronewtons contact force with only 10 V bias voltage. The fabricated miniature switch (80 × 50 × 0.95 µm) has indeed a pull-down voltage of 6 V and a contact resistance <2 Ω with 10 V bias applied. By measuring the S-parameters, the up-state capacitance has been fitted to 22 fF. The remarkable figure-of-merit Ron × Cup = 44 fs reflects the good performance of the device. A cycling test showed the device operated for 90 min without any charging problem noted.

A Novel Bidirectional Z-Shaped Thermally Actuated RF MEMS Switch for Multiple-Beam Antenna Array

In this paper RF MEMS switchis designed for dielectric-embedded electronically switched multiple-beam (DE-ESMB) antenna array. To achieve small stiffness without buckling, a novel bidirectional Z-shaped thermal actuator is used instead of V-shaped thermal actuator, which can generate large displacement and high contact force at low actuation voltage. With the actuation current from-0.6 A to 0.6 A, the electrothermal actuator can achieve a bidirectional motion in a dynamic range of-10.08 μm to 10.17 μm.RF performances are improved by suspending the structure 25 μm from the substrate using MetalMumps process. An ON state insertion loss of-0.14 dB at 10 GHz and an OFF state isolation of-67 dB at 10 GHz are achieved on low resistivity silicon substrate.