Next Generation LVAD

 

Left ventricular assist devices (LVAD) are battery operated mechanical pumps that help maintain the pumping ability of a heart that cannot effectively work on its own. Often referred to as "bridge to transplant" devices by clinicians across the continuum of care, these mechanical pumps can help a weak heart and "buy time" for a patient, who requires a heart transplant, and when donor hearts are not available. Primarily, these devices are used to treat patients in end-stage heart failure. While the bridge to transplant indication has been around for 15 years, clinicians are looking to explore possibilities of using these pumps as an alternative to transplantation. The long-term "destination therapies," as clinicians refer to it, have led to manufacturers work on simple designs to replicate the pulsatile flow of the heart. Also adding to the existing cup of woes of the clinical community is the size of the device and its reliability, where in most cases, first generation devices that were implanted were subjected to mechanical wears. These were large mechanically complex volume displacement pumps that gave away after a year and a half after implantation, and in most cases, the patients required a second surgical intervention. Now with manufacturers toying around with ideas of building devices that could address the aforementioned limitations, clinicians opine that these second and third generation devices could open new vistas to the cardiovascular community. Joining the LVAD fray is HeartWare. Although listed on the Australian Securities Exchange, HeartWare is a US medical device company, headquartered in Massachusetts, and with manufacturing activities based in Florida. While earlier generation LVADs employ mechanical bearings to suspend the internal spinning rotor, the HeartWare Ventricular Assist Device (HVAD) uses a combination of passive magnets and hydrodynamic forces to eliminate the need for mechanical bearings. The impeller is the only moving part in the device, and since the internal mechanism is wearless, the pump is expected to have a reliability profile of ten years or more.

Talking to Technical Insights, Howard Leibman, director, corporate development, HeartWare, said, "LVADs today are used almost exclusively as a bridge-to-transplant. There exists significant opportunity to expand the use of these devices out of this relatively small indication and into the so-called "destination therapy" indication, where the many thousands of patients who suffer advanced heart failure but who are not eligible for a transplant receive a device as a lifelong or "destination" treatment option. The reason that LVADs have historically been limited to the transplant population is that the older generation pumps have been large and unreliable. This has prompted HeartWare and other companies to develop smaller, more reliable pumps. The smaller size allows these second and third generation devices to be implanted by less invasive surgery. Their improved reliability profiles make them more suitable for providing long-term support.
The HeartWare HVAD is a very small centrifugal pump. With a volume of only 50 cc, it is designed to be implanted directly adjacent to the heart in the pericardial space, avoiding the abdominal surgery typically required to implant larger devices. Implantation above the diaphragm leads to a reduced surgery time and a less invasive procedure, potentially translating into important patient benefits.

At the core of the HVAD is the impeller, which spins at approximately 2400 revolutions per minute. The impeller is suspended within the pump housing through a combination of passive magnets in the one plane and a hydrodynamic thrust bearing in the other. Talking further on the benefits of the device, Leibman said, "Due to our hybrid magnetic and hydrodynamic mechanism for suspending the impeller, there are no points of physical contact between the impeller and the housing. Since there is no mechanical wear, we would expect the pump to be reliable over the long term. Also worth noting is that despite its small size, the HVAD device is capable of producing up to 10 litres/minute of blood flow, taking over completely from the native heart if required."
The hydrodynamic suspension is achieved by a gentle incline on the upper surfaces of the impeller blades. When the impeller spins, blood flows across these inclined surfaces, creating a "cushion" between the impeller and the pump housing.

Device reliability is expected to be enhanced through the use of dual motor stators with independent drive circuitry, allowing a seamless transition between dual and single stator mode if required. The pump's inflow cannula is integrated with the device itself, ensuring proximity between the heart and the pumping mechanism. This proximity is expected to facilitate ease of implant and help to ensure optimal blood flow characteristics. The use of a wide-bladed impeller and the clear flow paths through the system are expected to help minimize any risk of pump induced hemolysis (damage to blood cells) or thrombus (blood clotting).

The device was built inhouse. The company has about 26 patents filed toward the device. Project underway include the development of a new generation device called the MVAD (miniaturized ventricular assist device), which is approximately 1/3rd the size of the HVAD, and will be implanted through minimally invasive surgery. This device is currently in animal studies.
Elaborating on the funding received by the company, Leibman said, "Prior to 2005 the company was funded by US venture capital money. In January 2005 we completed an Initial Public Offering (IPO) on the Australian Stock Exchange ( ASX), raising 30 million AUD. Since then we have completed a further three public financings, raising approximately 30 million AUD in each of 2006, 2007 and 2008."

The device implantation has been done in 46 patients so far across five centers--Vienna, Hanover, Fairfield (UK), Sydney, and Perth. The company is expecting a device launch in Europe in early 2009 and has applied for the CE mark. Clinical trials, for using the device in the US, are currently underway across 28 Centres with 150 patients enrolled for the study and with one patient receiving the implant so far.

Details:

Howard Leibman

Director

Corporate Development

HeartWare Limited

Level 57, MLC Centre

19-29 Martin Place

Sydney NSW 2000.

Phone: + 61-2-9238-2064

Cell: +61-402-440-644

Fax: +61-2-9238-2063

E-ma
il: howard.leibman@heartware.com.au

URL: www.heartware.com.au

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