Myocardial function in aortic stenosis - insights from radial multilayer Doppler strain

Background Left ventricular (LV) radial tissue Doppler imaging (TDI) strain increases gradually from the subepicardial to the subendocardial layer in healthy individuals. A speckle tracking echocardiography study suggested this gradient to be reduced in parallel with increasing aortic stenosis (AS) severity. Methods We used TDI strain in 84 patients with AS (mean age 73 ± 10 years, 56% hypertensive) for superior assessment of layer strain. 38 patients had non-severe and 46 severe AS by aortic valve area corrected for pressure recovery. Peak systolic radial TDI strain was measured in the subendocardial, mid-myocardial and subepicardial layers of the basal inferior LV wall, each within a region of interest of 2 × 6 mm (strain length 2 mm). Results Radial strain was lower in the subepicardial layer (33.4 ± 38.6%) compared to the mid-myocardial and subendocardial layers (50.3 ± 37.3% and 53.0 ± 40.0%, respectively, both p < 0.001 vs. subepicardial). In the subendo- and midmyocardium, radial strain was lower in patients with severe AS compared to those with non-severe AS (p < 0.05). In multivariate regression analyses including age, heart rate, inferior wall thickness, hypertension, and AS severity, radial strain in the mid-myocardium was primarily attenuated by presence of hypertension (β = −0.23) and AS severity (β = −0.26, both p < 0.05), while radial strain in the subendocardium was significantly influenced by AS severity only (β = −0.35, p < 0.01). Conclusions In AS, both the AS severity and concomitant hypertension attenuate radial TDI strain in the inferior LV wall. The subendocardial radial strain is mainly influenced by AS severity, while midmyocardial radial strain is attenuated by both hypertension and AS severity

End-User Attitudes towards Location-Based Services and Future Mobile Wireless Devices: The Students' Perspective

Nowadays, location-enabled mobile phones are becoming more and more widespread. Various players in the mobile business forecast that, in the future, a significant part of total wireless revenue will come from Location-Based Services (LBS). An LBS system extracts information about the user’s geographical location and provides services based on the positioning information. A successful LBS service should create value for the end-user, by satisfying some of the users’ needs or wants, and at the same time preserving the key factors of the mobile wireless device, such as low costs, low battery consumption, and small size. From many users’ perspectives, location services and mobile location capabilities are still rather poorly known and poorly understood. The aim of this research is to investigate users’ views on the LBS, their requirements in terms of mobile device characteristics, their concerns in terms of privacy and usability, and their opinion on LBS applications that might increase the social wellbeing in the future wireless world. Our research is based on two surveys performed among 105 students (average student age: 24 years) from two European technical universities. The survey questions were intended to solicit the youngsters’ views on present and future technological trends and on their perceived needs and wishes regarding Location-Based Services, with the aim of obtaining a better understanding of designer constraints when building a location receiver and generating new ideas related to potential future killer LBS applications.Peer reviewe