Mechanical circulatory support

Theory of Pivoting Uncertainties: Advance Care Planning Among Individuals Living With Mechanical Circulatory Support

BACKGROUND

Individuals living with mechanical circulatory support (MCS) devices are confronted with risks for catastrophic outcomes such as stroke and systemic infection. Considering these complexities, ongoing advance care planning (ACP) is important for shared decision making.

OBJECTIVE

The purpose of this study was to describe how experiences of the MCS trajectory informed decision making about ACP.

METHODS

All aspects of the research were guided by constructivist grounded theory. Focused conversations were conducted with a semistructured interview guide.

RESULTS

A total of 24 community-dwelling patients living with MCS were interviewed (33% female; mean age, 60.6 years; 50% White). Participants were implanted with MCS (average duration, 29.8 months; bridge to transplant, 58%). Reflected in the narratives were tensions between initial expectations of living with the device in contrast with the realities that emerged over time. A crucial finding was that ACP decision making pivoted around the growing awareness of uncertainties in the MCS trajectory. Yet, clinicians were perceived to be silent in initiating ACP, and their reticence was understood as a sign of encouragement to hold on to hope for a heart transplant. The complex and dynamic decision-making processes around ACP were organized into the theory of pivoting uncertainties.

CONCLUSIONS

In this sample, patients were ready to share their concerns about the uncertainties of living with MCS and waited for MCS clinicians to initiate ACP. The theory of pivoting uncertainties is useful for elucidating the ebb and flow of ACP and lending clinicians' guidance for opportunities to initiate these sensitive conversations.

Non-parametric dynamical estimation of blood flow rate, pressure difference and viscosity for a miniaturized blood pump

Blood pumps are becoming increasingly important for medical devices. They are used to assist and control the blood flow and blood pressure in the patient's body. To accurately control blood pumps, information about important hydrodynamic parameters such as blood flow rate, pressure difference and viscosity is needed. These parameters are difficult to measure online. Therefore, an accurate estimation of these parameters is crucial for the effective operation of implantable blood pumps. In this study, in vitro tests with bovine blood were conducted to collect data about the non-linear dependency of blood flow rate, flow resistance (pressure difference) and whole blood viscosity on motor current and rotation speed of a prototype blood pump. Gaussian process regression models are then used to model the non-linear mappings from motor current and rotation speed to the hydrodynamic variables of interest. The performance of the estimation is evaluated for all three variables and shows very high accuracy. For blood flow rate - correlation coefficient (r2) = 1, root mean squared error (RMSE) = 0.31 ml min^-1, maximal error (ERRmax) = 9.31 ml min^-1; for pressure r2 = 1, RMSE = 0.09 mmHg, ERRmax = 8.34 mmHg; and for viscosity r2 = 1,RMSE = 0.09 mPa.s, ERRmax = 0.31 mPa⋅s. The current findings suggest that this method can be employed for highly accurate online estimation of essential hydrodynamic parameters for implantable blood pumps.

Ultrasonic blood flowmeter with a novel Xero algorithm for a mechanical circulatory support system

Mechanical circulatory support systems (MCSSs) are crucial devices for transplants in patients with heart failure. The blood flowing through the MCSS can be recirculated or even stagnated in the event of critical blood flow issues. To avoid emergencies due to abnormal changes in the flow, continuous changes of the flowrate should be measured with high accuracy and robustness. For better flowrate measurements, a more advanced ultrasonic blood flowmeter (UFM), which is a noninvasive measurement tool, is needed. In this paper, we propose a novel UFM sensor module using a novel algorithm (Xero) that can exploit the advantages of both conventional cross-correlation (Xcorr) and zero-crossing (Zero) algorithms, using only the zero-crossing-based algorithm. To ensure the capability of our own developed and optimized ultrasonic sensor module for MCSSs, the accuracy, robustness, and continuous monitoring performance of the proposed algorithm were compared to those of conventional algorithms after application to the developed sensor module. The results show that Xero is superior to other algorithms for flowrate measurements under different environments and offers an error rate of at least 0.92%, higher robustness for changing fluid temperatures than conventional algorithms, and sensitive responses to sudden changes in flowrates. Thus, the proposed UFM system with Xero has a great potential for flowrate measurements in MCSSs.

Proteomics highlights decrease of matricellular proteins in left ventricular assist device therapy†

OBJECTIVES

We investigated the impact of mechanical unloading with a left ventricular assist device (LVAD) on the myocardial proteome.

METHODS

We collected 11 patient-matched samples of myocardial left ventricular tissue of patients with non-ischaemic dilate cardiomyopathy, harvested at time of LVAD implant ('pre-LVAD') and heart transplant ('post-LVAD'). Samples were studied by quantitative proteomics. Further we performed histological assessment of deposited collagens and immune infiltration in both pre- and post-LVAD samples.

RESULTS

A core set of  >1700 proteins was identified and quantified at a false discovery rate  <1%. The previously established decrease post-LVAD of alpha-1-antichymotrypsin was corroborated. We noted a post-LVAD decrease of matricellular proteins and proteoglycans such as periostin and versican. Also, proteins of the complement system and precursors of cardiac peptide hormones were decreased post-LVAD. An increase post-LVAD was evident for individual proteins linked to the innate immune response, proteins involved in diverse metabolic pathways, and proteins involved in protein synthesis. Histological analysis did not reveal significant alterations post-LVAD of deposited collagens or immune infiltration. The proteomic data further highlighted a pronounced inter-patient heterogeneity with regards to the impact of LVAD therapy on the left ventricular myocardial proteome. Finally, the proteomic data showed differential proteolytic processing in response to LVAD therapy.

CONCLUSIONS

Our findings underline a strong impact of LVAD therapy on the left ventricular myocardial proteome. Together with previous studies, protein markers of LVAD therapy such as alpha-1-antichymotrypsin are becoming apparent. Further, matricellular proteins are emerging as important components in response to LVAD therapy.

Doppler Ultrasound Evaluation of Circulatory Support Devices

In the setting of mechanical circulatory support devices, including ventricular assist devices, extracorporeal membrane oxygenation, intraaortic balloon pumps, and the total artificial heart, the spectral Doppler waveform is significantly altered, reflecting systemic hemodynamic changes. As the prevalence of these devices increases, a better understanding of both the devices themselves and their associated Doppler ultrasound findings is necessary for accurate image interpretation. This article reviews the clinical indications, pathophysiology, and sonographic findings of these devices, with emphasis on the variation in arterial Doppler waveforms that can be seen with normal function, as well as the major complications.

Implantation of a left ventricular assist device with mini-pericardiotomy technique

The left ventricular assist device may be a lifesaving therapy for a patient awaiting a heart transplant. The most common complications of this device are mediastinal bleeding, infections, embolic events, right-sided heart failure, and mediastinal adhesions. We are reporting a patient who had a Levitronix left ventricular assist device implanted with mini-pericardiotomy technique for bridging to heart transplant.

Quality and adequacy of dietary intake in a southern urban heart failure population

BACKGROUND

Few studies have examined the quality and adequacy of dietary intake in patients attempting to limit sodium.

OBJECTIVE

The aim of this study was to provide a comprehensive analysis of the dietary intake of persons with heart failure (HF) in the Southern United States who have been advised to limit their sodium intake.

METHODS

Three-day food diaries were completed by 114 New York Heart Association class II and III persons with HF enrolled in a family partnership intervention study, which were reviewed by a dietitian and analyzed using validated nutritional software. The Harris-Benedict equation for sedentary adults was used to determine macronutrient intake adequacy. Demographic information and clinical data were obtained through patient report and medical record review.

RESULTS

Dietary sodium ingestion ranged from 522 to 9251 mg/d (mean [SD], 2671 [1432] mg/d), with 38 (33.3%) individuals consuming the recommended 2000 mg/d or less in this sample (age, 28-78 years; 64.0% men; 57.0% African American). Mean (SD) caloric intake for the total sample was 1674 (636) kcal/d, with participants eating 99% of the recommended daily allowance (RDA) of protein, 63% of the RDA of carbohydrates, and 89% of the RDA of fat. Participants eating 2000 mg or less of sodium consumed significantly less calories (P < .001), protein (P < .001), carbohydrates (P = .008), and fat (P < .001), but not fiber (P = .103), compared with those consuming more than 2000 mg of sodium after adjusting for body mass index. When analyzed by amount of sodium consumption, persons ingesting 2000 mg or less of sodium per day ate significantly less grains (P = .001) and meat and beans (P = .004) and had less intake of the micronutrients calcium (P < .001), zinc (P = .002), and thiamine (P = .05).

CONCLUSION

Only one-third of participants with HF who have been instructed on a low-sodium diet reported consuming the RDA of 2000 mg or less, indicating the need for further dietary instruction with a particular focus on modifying the Southern US diet.