Seismic reflection survey using Vibroseis in Zama city and Hiratsuka city, Kanto basin, central Japan

Seismic reflection survey using Vibroseis with a line length of 13km was conducted around Zama city and Hiratsuka city, in the southwest part of the Kanto basin. Seismic refraction records were also acquired by shooting at the both ends of the survey line with over 100 vertical stacks. From the seismic section, a clear reflector interpreted as the top of the acoustic basement is identified. The basement has a very complex structure with depths varying from 200m to 1200 m. As a result of a refraction method analysis, the P-wave velocity of the basement is estimated to be about 4.3 km/s. Comparing acoustic logging data of Atsugi observation well, it corresponds to the lower part of the Aikawa Group (Miocene volcanics). The interpreted basement has a different velocity and geology from that commonly observed in the Kanto plain (4.8-5.5 km/s layer). Above the basement, sediments can be divided into two parts by a remarkable reflector seen at depths of 200 300m at both ends of the line. As this reflector has a velocity of 2.3-2.4 km/s, this corresponds to the boundary between the Sagami Group (Quaternary sediments) and the Aikawa Group observed at the Atsugi well. The Sagami Group contains sharp and continuous reflectors with flat or gentle dips, whereas the upper part of the Aikawa Group is accompanied with considerable folds and faults

Mid-term feasibility and safety of downgrade procedure from defibrillator to pacemaker with cardiac resynchronization therapy

Backgrounds: Some patients who undergo implantation of cardiac resynchronization therapy with defibrillator (CRT-D) survive long enough, thus requiring CRT-D battery replacement. Defibrillator therapy might become unnecessary in patients who have had significant clinical improvement and recovery of left ventricular ejection fraction (LVEF) after CRT-D implantation. Methods: Forty-nine patients who needed replacement of a CRT-D battery were considered for exchange of CRT-D for cardiac resynchronization therapy with pacemaker (CRT-P) if they met the following criteria: LVEF >45%; the indication for an implantable cardioverter defibrillator was primary prevention at initial implantation and no appropriate implantable cardioverter defibrillator therapy was documented after initial implantation of the CRT-D. Results: Seven patients (14.2%) were undergone a downgrade from CRT-D to CRT-P without any complications. No ventricular tachyarrhythmic events were observed during a mean follow-up of 39.7 ± 21.1 months and there was no significant change in LVEF between before and 1 year after device replacement (53.5% ± 6.2% vs. 56.4% ± 7.3%, P = 0.197). Conclusions: This study confirmed mid-term feasibility and safety of downgrade from CRT-D to CRT-P alternative to conventional replacement with CRT-D. Keywords: Cardiac resynchronization therapy, Cardioverter defibrillator, Downgrade, Primary prevention, Ventricular tachyarrhythmi