Heartware Ventricular Assist System, Essay Example

The HeartWare Ventricular Assist System is a device used to assist in the treatment of heart failure at an advanced stage of the condition. It is a mechanical devise that is miniaturized for heart treatment. This device has been developed by HeartWare International, Inc. (HeartWare). This is a medical device company that has developed a family of implantable Left Ventricular Assist Devices (also known as LVADs) that used for the treatment of advanced heart failure.  The HeartWare Ventricular Assist System is leading product among those developed by HeartWare. The figure below shows the Heartware Ventricular Assist System.

HeartWare Ventricular Assist System has not been fully commercialized in the United States, even though it is commercially available in Europe, as it is currently still in the clinical trial stage. Once the clinical trials are complete the company shall obtain approval from FDA (Food and Drug Administration) to develop the product commercially. Trials have already completed enrollment of a 50-patient international clinical trial. In January 2009, the company received CE Mark approval for the product. The CE mark is the conformity mark of products placed in the European Economic Area. The product is subject to an ongoing bridge-to-transplant clinical trial under which the company will enroll up to 150 patients at a maximum of 28 participating centers. This shall ensure evaluation of the product.

Heart failure is a heart condition that is considered a serious degenerative, terminal disease. The condition affects more that 20 million patients all over the worldwide. Of all these patients close to one million patients suffer from the advanced stage of heart failure which require heart transplant. Heart transplant is the best option to treat these conditions; however only approximately 3,000 donor hearts are available worldwide each year from willing donors. To care for the rest, LVADs are used to bridge patients until a donor heart becomes available. This is called bridge-to-transplant therapy. Increasingly the LAVDs are being used as a long term alternative to heart transplant. This is called destination therapy. LAVD’s were developed more that twenty years ago and have been in use since 1989.

The Ventricular Assist System consists of a centrifugal pump that can pump up to 10 liters a minute of blood flow. The pump is made so as to be placed above the diaphragm and next to the heart. This is to avoid the possibility of abdominal surgery that would be required. The product is designed to supplement the pumping of blood by the patient’s weak heart.

The LVAD is composed of “wireless” suspension mechanism, a miniaturization path and optimal blood flow paths. The wireless suspension mechanism consists of some sort of a platform. It has a rotor or impeller, which is the only moving part in the pump and a bearing. The platform is the proprietary use of a suspension system for suspending the impeller or the rotor. Used to suspend the rotor are a combination of passive magnets and a hydrodynamic thrust bearing. These bearings work by establishing a cushion of blood between the rotor and the pump housing. When power is applied to the device, the rotor rotates. Wearing of the device is protected by ensuring that there is no point of mechanical contact with the pump. The absence of a mechanical bearing is supposed to ensure that the device has a long period reliability and has a reduced risk of physical damage to blood cells as they pass through the pump.

The miniaturization path is established by the hybrid suspension system. This ensures that there is a significant downsizing of the pump technology. The Hear ware Ventricular system has a miniaturized centrifugal pump. This pump is small in size to ensure that it can be implanted above the diaphragm. More post operative and improved patient service outcomes are expected to be enhanced by the reduced procedural invasiveness. The company is working towards coming up with a family of miniaturized pumps that shall be implanted by minimal invasive surgery.

The pump is designed to consist of an impeller with wide blades so as to provide optimal blood flow paths through the system. It also incorporates an integrated inflow canola to ensure there is an access between the heart and the pumping mechanism. Potential points of blood turbulence, also known as stasis, through the system are eliminated due to the proximity between the heart and the pumping mechanism. This process ensures that there is minimal damage to the blood by way of blood clotting, also known as thrombus or through the rupturing of the blood cells membranes (hemolysis) which are key clinical requirements. The figures below represent images illustrating the operation of the system.

The Heartware Left Ventricular Assist System has a small implantable centrifugal blood pump called the HVADTM pump which is designed to draw blood from the apex of the left ventricle and to push to an outflow graft connected to the ascending aorta. This is the device that can pump blood at the rate more than ten liters in a minute. The HVAD pump which has a capacity of 50cc is designed such that it can be implanted in the pericardial space which is just next to the heart. A short surgery time and a quick recovery can be achieved through the implantation above the diaphragm.

The impeller or the rotor, which can rotate at speed of 2,000 revolutions per minute and 3,000 revolutions per minute, is the only moving part of the HAVD pump. It is suspended in the pump caging or housing by a series of inactive magnets and a hydrodynamic thrust bearing. A gentle incline on the upper surface of the impeller blades ensures that suspension is achieved. Blood flows through the inclined surfaces, when the rotor rotates thus forming a cushion between the rotor (impeller) and the pump caging or housing. The rotor (impeller) and the pump caging do not get into physical contact with each other.

The utilization of dual motor stators is used to enhance the device reliability. They have an independent drive circuit allows a transition between single and dual stator mode that is seamless. Proximity of heart and pumping mechanism is ensured by the integration of the pump’s inflow canola and the device. The proximity of these two parts facilitates the ease of implantation and ensures optimal flow of blood. The risk of pump induced hemolysis or thrombus are minimized by the use of the clear paths where blood flows and the wide bladed rotor.

The diagram below shows a representation of the inserted Ventricular Assist System:

The system is designed to help the heart of a patient pump blood through the body of the patience by pumping blood from the left side of the heart into the aorta. The aorta is a huge vessel that supplies blood to the rest of the body from the heart. The device rests inside the patient’s chest. The impeller within the device are made to rotate by two motor stators inside the pump housing. These rotating impellers ar the ones that pump blood throguh the system. A driveline or a cable is used to connect the device to an controller that is worn outside the body of the patient. A battery pack consisting of one or two batteries and an adaptor connected to an electricity outlet are used to power the controller. The controller provides the heart failure patient with a signal or an alarm on the how the system operates and also operates the pump. The battery pack and the controller are carried in a case carried by the patient.

The figures below shows the components of the Heartware’s Left Ventricular Assist System with a narative on each of them.

These are a set of surgical tools and accessories designed by Heartware that are used in the implantation of the HVAD device.  Each pump kit contains a full set of these single use-surgical tools. The accessories in the pump kit consists of an apical coring tool to core the myocardium for left ventricular cannulation, a sewing ring tool that are used to tighten the screw n t apical ring and a tunneler used to tunnel the percutaneous driveline to the exit site.

Complications arising out of the HVAD operations can be classified as temporal occurrence and permanent occurrence. The short term and acute complications include the thromboembolism which occurs as a result of the contact of the body cells with and a foreign surface, hemorrhage which include complications such as multiorgan failure, hypoprfusion or intercranial bleeding and ventricular failure. Long term complications include infections such as pneumonia, urinary tract infections and mediastinitis.

In summary, the development of the Ventricular Assist Devices has been able to save many lives of people with heart failures. Research continues in this area t fully maximize the benefits of Ventricular Assist Devices.

References

HeartWare International, Inc (2009). HeartWare Ventricular Assist System. Retrieved on 24 September 2009 from <http://www.heartware.com.au/IRM/content/usa/products_HVAD.html>

Walter Kluwer Hearlth. (2009). Complications in patients with Ventricular assist Devices. Retrieved from <http://www.nursingcenter.com/prodev/ce_article.asp?tid=827969>