HeartWare® HVAD® System



Fig. 53.1
The HeartWare HVAD system



Upon its introduction to the market in 2009, the HVAD system featured several important advantages over the contemporary competition. The device has an integrated inflow cannula that is inserted into the left ventricle apex and an outflow graft that is anastomosed to the arterial system. The integrated inflow cannula minimizes the pump footprint within the chest cavity and allows the pump body to be situated solely within the pericardial space, eliminating the need for a pump pocket (◘ Fig. 53.2) [6]. Pericardial placement is also advantageous in ensuring stable positioning that adapts to the ventricular and body habitus changes that occur post-implantation.

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Fig. 53.2
The HeartWare HVAD pump implanted in the pericardial space

Additionally, despite its small size (160 g weight, 50 mL displacement volume), the HVAD pump allows for application in a broad patient population without compromising clinical performance. Its design allows it to fit within small-framed patients yet is powerful enough to support large body habitus patients where circulatory demand may be higher. The key to developing a successful implantation technique was based on the standardization of the system’s surgical tools. The simplistic design of the ventricle coring tool, sewing ring wrench, hex driver, and tunneler minimized user variability and allowed hospitals with varying levels of experience in the field of mechanical circulatory support (MCS) to achieve consistently excellent results.

The HVAD pump was also revolutionary in its application of magnetic suspension and hydrodynamic thrust bearing technology. Briefly, the pump consists of two redundant motor stators located within the upper and lower housing. Pump rotational speed ranges from 1800 RPM to 4000 RPM, and the device may generate up to 10 L/min of blood flow. It has one moving component – the impeller – which is passively suspended by magnets located within the pump centerpost. Hydrodynamic thrust bearings located on the four wide-channel impeller blades provide the necessary axial forces to balance the impeller’s position within the pump housing. The success of the HVAD pump validates the concept that hydrodynamic thrust bearings may be used as an alternative to mechanical bearings to achieve a durable, “wearless” design. An impeller that is contact-free may theoretically operate for longer periods without the failures typically seen of its mechanical bearing counterparts [7].

As the field of MCS advanced, patient survival increased and ergonomics began to play a more prominent role in device design. Trends in pump miniaturization were similarly adopted for the peripheral equipment to enhance the patient’s quality of life. The HVAD system controller is a wearable controller (13.4 × 10.5 × 5.1 cm) weighing 0.5 kg. This was the first MCS controller to have a display that provides real-time pump parameters (rotational speed, power consumption, and estimated VAD flow), alarm information, and troubleshooting messages to the patient. An intelligent interface between the controller and monitor allows users to view accurate pump flow estimation waveforms [8] with 50 Hz resolution. Clinicians are able to more effectively manage their patients by viewing both real-time waveforms as well as the historical trend information. Controller log files downloaded via the monitor provide insight to enhance patient management [9].

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Nov 3, 2017 | Posted by in CARDIOLOGY | Comments Off on HeartWare® HVAD® System

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