Worsening Renal Function in Cardiac Mechanical Support

Mock circulatory loops used for testing cardiac assist devices: A review of computational and experimental models

Heart failure is a major health risk, and with limited availability of donor organs, there is an increasing need for developing cardiac assist devices (CADs). Mock circulatory loops (MCL) are an important in-vitro test platform for CAD's performance assessment and optimisation. The MCL is a lumped parameter model constructed out of hydraulic and mechanical components aiming to simulate the native cardiovascular system (CVS) as closely as possible. Further development merged MCLs and numerical circulatory models to improve flexibility and accuracy of the system; commonly known as hybrid MCLs. A total of 128 MCLs were identified in a literature research until 25 September 2020. It was found that the complexity of the MCLs rose over the years, recent MCLs are not only capable of mimicking the healthy and pathological conditions, but also implemented cerebral, renal and coronary circulations and autoregulatory responses. Moreover, the development of anatomical models made flow visualisation studies possible. Mechanical MCLs showed excellent controllability and repeatability, however, often the CVS was overly simplified or lacked autoregulatory responses. In numerical MCLs the CVS is represented with a higher order of lumped parameters compared to mechanical test rigs, however, complex physiological aspects are often simplified. In hybrid MCLs complex physiological aspects are implemented in the hydraulic part of the system, whilst the numerical model represents parts of the CVS that are too difficult to represent by mechanical components per se. This review aims to describe the advances, limitations and future directions of the three types of MCLs.

Ventricular Assist Devices and Chronic Kidney Replacement Therapy: Technology and Outcomes

Heart failure and kidney failure are very common conditions, precipitating and exacerbating each other. Left ventricular assist devices (LVADs) represent a relatively new technology for treatment of advanced heart failure. Kidney dysfunction, if present, makes candidate selection for LVADs challenging and contributes to multiple complications while the patients are on an LVAD support. Although kidney function generally improves after LVAD implantation, some patients develop acute and then chronic kidney disease sometimes requiring kidney replacement therapies (KRTs). Overall, chronic KRT in LVAD recipients is feasible and well tolerated, but routine technique of blood pressure monitoring should be adjusted to the continuous blood flow. Both hemodialysis and peritoneal dialysis can be used. Unique challenges for chronic KRT posed by the presence of LVAD are discussed in this review.

Plasma trimethylamine n-oxide is associated with renal function in patients with heart failure with preserved ejection fraction

Background

Heart failure with preserved ejection fraction (HFpEF) is an emerging global health problem with less awareness. Renal dysfunction in HFpEF is associated with worse outcome. However, there is lack of rapid, noninvasive and accurate method for risk stratification in HFpEF and renal dysfunction. This study aimed to explore the utility of plasma trimethylamine n-oxide (TMAO) for evaluation of HFpEF and renal function.

Methods

Plasma TMAO levels were measured in total 324 subjects comprising 228 HFpEF patients and 96 healthy controls.

Results

TMAO levels were significantly elevated in patients with HFpEF compared with controls (12.65(9.32–18.66) μg/l vs 10.85(6.35–15.58) μg/l, p <  0.01). Subjects in higher TMAO tertile group had more incidences of HFpEF ((78.5%) in tertile 3 vs (73.39%) in tertile 2 vs (59.26%) in tertile 1, p <  0.01). TMAO concentrations were inversely correlated with estimated glomerular filtration rate (eGFR) and HFpEF patients with impaired renal function (eGFR < 60 ml/min/1.73 m²) had higher TMAO than those with normal eGFR (≥ 60 ml/min/1.73 m²) (14.18(10.4–23.06) μg/l vs 10.9(7.48–15.47) μg/l, p < 0.01). Increased TMAO levels were independently associated with higher risk of HFpEF (OR = 3.49, 95% CI: 1.23–9.86, p = 0.02) and renal dysfunction (OR = 9.57, 95% CI: 2.11–43.34, p < 0.01) after adjustment for multiple traditional risk factors. Furthermore, TMAO had good performance at distinguishing HFpEF from controls (AUC = 0.63, p < 0.01), and renal dysfunction from normal renal function in HFpEF (AUC = 0.67, p < 0.01).

Conclusion

In this cross-sectional study, HFpEF and renal function were closely related with plasma TMAO levels and TMAO may serve as a diagnostic biomarker for HFpEF and renal function.