Transplant Outcomes in Destination Therapy Left Ventricular Assist Device Patients

Percutaneous intravascular micro-axial blood pump: current state and perspective from engineering view

The utilization of a minimally invasively placed catheter-mounted intravascular micro-axial flow blood pump (IMFBP) is increasing in the population with advanced heart failure. The current development of IMFBPs dates back around the 1990s, namely the Hemopump with a wire-drive system and the Valvopump with a direct-drive system. The wire-drive IMFBPs can use a brushless motor in an external console unit to transmit rotational force through the drive wire rotating the impeller inside the body. The direct-drive IMFBPs require an ultra-miniature and high-power brushless motor. Additionally, the direct-drive system necessitates a mechanism to protect against blood immersion into the motor. Therefore, the direct-drive IMFBPs can be categorized into two types of devices: those with seal mechanisms or those with sealless mechanisms using magnetically coupling. The IMFBPs can be classified into two groups depending on their purpose. One group is for cardiogenic shock following a heart attack or for use in high-risk percutaneous coronary intervention (PCI), and the other group serves the purpose of acute decompensated heart failure. Both direct-drive IMFBPs and wire-drive IMFBPs have their own advantages and disadvantages, and efforts are being made to develop and improve, and clinically implement them, leveraging their own strengths. In addition, there is a possibility that innovative new devices may be invented. For researchers in the field of artificial heart development, IMFBPs offer a new area of research and development, providing a novel treatment option for severe heart failure.

Transcutaneous Pulsed RF Energy Transfer Mitigates Tissue Heating in High Power Demand Implanted Device Applications: In Vivo and In Silico Models Results

This article presents the development of a power loss emulation (PLE) system device to study and find ways of mitigating skin tissue heating effects in transcutaneous energy transmission systems (TETS) for existing and next generation left ventricular assist devices (LVADs). Skin thermal profile measurements were made using the PLE system prototype and also separately with a TETS in a porcine model. Subsequent data analysis and separate computer modelling studies permit understanding of the contribution of tissue blood perfusion towards cooling of the subcutaneous tissue around the electromagnetic coupling area. A 2-channel PLE system prototype and a 2-channel TETS prototype were implemented for this study. The heating effects resulting from power transmission inefficiency were investigated under varying conditions of power delivery levels for an implanted device. In the part of the study using the PLE setup, the implanted heating element was placed subcutaneously 6-8 mm below the body surface of in vivo porcine model skin. Two operating modes of transmission coupling power losses were emulated: (a) conventional continuous transmission, and (b) using our proposed pulsed transmission waveform protocols. Experimental skin tissue thermal profiles were studied for various levels of LVAD power. The heating coefficient was estimated from the porcine model measurements (an in vivo living model and a euthanised cadaver model without blood circulation at the end of the experiment). An in silico model to support data interpretation provided reliable experimental and numerical methods for effective wireless transdermal LVAD energization advanced solutions. In the separate second part of the study conducted with a separate set of pigs, a two-channel inductively coupled RF driving system implemented wireless power transfer (WPT) to a resistive LVAD model (50 Ω) to explore continuous versus pulsed RF transmission modes. The RF-transmission pulse duration ranged from 30 ms to 480 ms, and the idle time (no-transmission) from 5 s to 120 s. The results revealed that blood perfusion plays an important cooling role in reducing thermal tissue damage from TETS applications. In addition, the results analysis of the in vivo, cadaver (R1Sp2) model, and in silico studies confirmed that the tissue heating effect was significantly lower in the living model versus the cadaver model due to the presence of blood perfusion cooling effects.

Durable mechanical circulatory support as bridge to heart transplantation

PURPOSE OF REVIEW

Durable mechanical circulatory support (MCS) technology has changed over time as devices have evolved from pulsatile to continuous flow support. In this review, we discuss recent data and substantial changes to current practice as it pertains to the subject of current era durable left ventricular assist devices (LVADs) as a bridge to heart transplantation.

RECENT FINDINGS

The results of heart transplantation in patients bridged with durable LVAD support are satisfactory even after prolonged duration of support. Reports of recent experience with LVAD related infection suggest that this complication has limited impact on post-transplant outcomes. Important sex-related disparities continue to exist following durable LVAD implantation. Recent changes in the United Network for Organ Sharing donor heart allocation policy have resulted in a drastic decline in the use of durable LVAD support for Bridge to Transplant in the United States.

SUMMARY

Durable MCS in the form of LVAD as a BTT strategy continues to evolve over time. Optimization of its role in the treatment of end-stage heart failure, particularly in females will need to be the focus of future research.