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 grafting.

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: Insights From the Nationwide Inpatient Sample 2004 to 2016.

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.

Advances in managing the noninfected open chest after cardiac surgery: Negative-pressure wound therapy.

OBJECTIVE: The objective of this study was to compare safety and clinical effectiveness of negative-pressure wound therapy (NPWT) with traditional wound therapy for managing noninfected open chests with delayed sternal closure after cardiac surgery. METHODS: From January 2000 to July 2015, 452 of 47,325 patients who underwent full sternotomy left the operating room with a noninfected open chest (0.96%), managed using NPWT in 214-with frequency of use rapidly increasing to near 100%-and traditionally in 238. Predominant indications for open-chest management were uncontrolled coagulopathy or hemodynamic compromise on attempted chest closure. Weighted propensity-score matching was used to assess in-hospital complications and time-related survival. RESULTS: NPWT and traditionally managed patients had similar high-risk preoperative profiles. Most underwent reoperations (63% of the NPWT group and 57% of the traditional group), and 21% versus 25% were emergency procedures. Reexplorations for bleeding were less common with NPWT versus traditional wound therapy (n = 63 [29%] vs 104 [44%], P = .002). Median duration of open-chest to definitive sternal closure was 3.5 days for NPWT versus 3.1 for traditionally managed patients (P[log rank] = .07). Seven patients (3.3%) were converted from NPWT to traditional therapy because of hemodynamic intolerance and 6 (2.5%) from traditional to NPWT. No NPWT-related cardiovascular injuries occurred. Among matched patients, NPWT was associated with better early survival (61% vs 44% at 6 months; P = .02). CONCLUSIONS: NPWT is safe and effective for managing noninfected open chests after cardiac surgery. By facilitating open-chest management and potentially improving outcomes, it has become our therapy of choice and perhaps has lowered our threshold for leaving the chest open after cardiac surgery.

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.

Mechanical circulatory support for the right ventricle in the setting of a left ventricular assist device.

Right ventricular failure is a difficult problem to manage and typically carries a dismal prognosis. In the setting of post-left ventricular assist device implantation (LVAD), right ventricular dysfunction both in the early and late stages is of particularly high incidence and concern. There are currently no agreed upon preoperative algorithms to predict patients at risk for this problem, thus adding another level of complexity to treatment. Furthermore, there is no current technology available for chronic right ventricular support and the devices currently in use are LVADS modified to adapt to the right circulatory system. This review provides an overview of right ventricular failure, particularly after LVAD implantation, and describes the survival outcomes and continued challenges in this area.

Myocardial recovery: a focus on the impact of left ventricular assist devices.

Heart failure remains one of the most prevalent diseases worldwide and in recent decades, left ventricular assist devices (LVADs) have become an important treatment option. With increasing device experience, there is particular interest in the use of LVADs as a bridge to recovery that allows the patient's heart to undergo reverse remodeling, whereby the device can be explanted and the heart can function at an improved state. There are many considerations that play a role in this process, including the ability of the device to unload the heart, the innate physiology of the heart to recover and the use of concomitant therapies. This review provides an overview of the most current literature as it pertains to these processes and gives a view into the future directions of LVADs as a tool for achieving myocardial recovery.