Hysteresis-free and high sensitivity strain sensing of ionically conductive hydrogels

Hydrogels are promising materials for soft and implantable strain sensors owing to their large compliance (E<100 kPa) and significant extensibility (εmax >500%) compared to other polymer networks. Further, hydrogels can be functionalized to seamlessly integrate with many types of tissues. However, most current methods attempt to imbue additional electronic functionality to structural hydrogel materials by incorporating fillers with orthogonal properties such as electronic or mixed ionic conduction. Although composite strategies may improve performance or facilitate heterogeneous integration with downstream hardware, composites complicate the path for regulatory approval and may compromise the otherwise compelling properties of the underlying structural material. Here we report hydrogel strain sensors composed of genipin-crosslinked gelatin and dopamine-functionalized poly(ethylene glycol) for in vivo monitoring of cardiac function. By measuring their impedance only in their resistive regime (>10 kHz), hysteresis is reduced and the resulting gauge factor is increased by ~50x to 1.02±0.05 and 1.46±0.05 from approximately 0.03-0.05 for PEG-Dopa and genipin-crosslinked gelatin respectively. Adhesion and in vivo biocompatibility are studied to support implementation of strain sensors for monitoring cardiac output in porcine models. Impedance-based strain sensing in the kilohertz regime simplifies the piezoresistive behavior of these materials and expands the range of hydrogel-based strain sensors.

Radial artery or saphenous vein for Coronary artery bypass grafitng

Coronary artery disease (CAD) is the most common cardiovascular disease worldwide, affecting over 18 million American adults. Coronary artery bypass grafting (CABG) is the standard of care for patients with left main or triple vessel CAD. Historically, the saphenous vein (SV) has been utilized to bypass the majority of the coronary vessels in patients undergoing CABG, but more recent data suggest that the use of the radial artery (RA), rather than the SV, is associated with improved cardiac outcomes and better survival. The aim of this review is to summarize the current literature on the use of RA and SV for CABG in patients with multivessel CAD.

Sex-Based Differences in Left Ventricular Assist Device Utilization

Background:

Women comprise approximately one-third of the advanced heart failure population but may receive fewer advanced heart failure therapies including left ventricular assist devices (LVADs). During the early pulsatile-flow device era, women had higher post-LVAD mortality and increased complications. However, knowledge about these differences in the continuous-flow device era is limited. Therefore, we sought to explore temporal trends in LVAD utilization and post-LVAD mortality by sex.

Methods and Results:

Patients with LVAD implantation from 2004 to 2016 were identified using the Nationwide Inpatient Sample. Trends in LVAD utilization and post-LVAD inpatient mortality were compared by sex and device era. Although LVADs are being increasingly utilized for patients with advanced systolic heart failure, women continue to represent a smaller proportion of LVAD recipients—25.8% in 2004 to 21.9% in 2016 ( P for trend, 0.91). Women had increased inpatient mortality after LVAD implantation compared with men in the pulsatile-flow era (46.9% versus 31.1%, P <0.0001) but not in the continuous-flow era (13.3% versus 12.1%, P =0.27; P for interaction=0.0002). Inpatient mortality decreased for both sexes over time after LVAD, with a sharp fall in 2008 to 2009. Female sex was independently associated with increased post-LVAD inpatient mortality beyond adjustment for demographics and risk factors during the pulsatile-flow era (odds ratio, 2.13; 95% CI, 1.45–3.10; P <0.0001) but not during the continuous-flow era (1.18; 0.93–1.48; P =0.16).

Conclusions:

Although utilization of LVAD therapy increased over time for both sexes, LVAD implantation remains stably lower in women, which may suggest a potential underutilization of this potentially life-saving therapy. Prospective studies are needed to confirm these findings.

Organ-mounted robot localization via function approximation

BACKGROUND

Organ-mounted robots adhere to the surface of a mobile organ as a platform for minimally invasive interventions, providing passive compensation of physiological motion. This approach is beneficial during surgery on the beating heart. Accurate localization in such applications requires accounting for the heartbeat and respiratory motion. Previous work has described methods for modeling quasi-periodic motion of a point and registering to a static preoperative map. The existing techniques, while accurate, require several respiratory cycles to converge.

METHODS

This paper presents a general localization technique for this application, involving function approximation using radial basis function (RBF) interpolation.

RESULTS

In an experiment in the porcine model in vivo, the technique yields mean localization accuracy of 1.25 mm with a 95% confidence interval of 0.22 mm.

CONCLUSIONS

The RBF approximation provides accurate estimates of robot location instantaneously.