HeartWare Heart Pump Shows Positive Results in Clinical Study
by MedGadget 2009 | Submitted Tuesday Nov 17, 2009 [06:32 AM]
The left ventricular assist device is designed to provide a bridge to heart transplant patients, improving their cardiac function while they await a donor organ.
A study of the Framingham, Mass.-based firm's miniature heart pump shows a 90 percent survival rate six months after implantation. HeartWare International Inc. released data from a clinical trial of its miniature heart pump in patients with end-stage heart failure, showing survival rates of 90 percent and 84 percent after six months and two years, respectively.
Data collected from a 50-patient trial aimed at winning CE Mark approval in the European Union (which was granted in January) showed a six-month survival rate of 90 percent, according to a regulatory filing. Two years after implantation the survival rate was 84 percent. Patients 60 years and older had a survival rate of 93 percent.
The study also showed an 80 percent reduction in post-implantation re-hospitalizations in the 12 months after the procedure, compared with the 12 months preceding implantation. Eight patients who received the device died, four from multi-organ failure, two from sepsis and two from hemorrhagic stroke.
The HeartWare Pump
At the core of the HeartWare Left Ventricular Assist System is a small implantable centrifugal blood pump called the HVADTM Pump. The pump is designed to draw blood from the apex of the left ventricle and to propel it through an outflow graft connected to the patient's ascending aorta. The device is capable of generating up to 10 liters per minute of blood flow.
With a displaced volume of only 50cc, the HVADTM pump is designed to be implanted in the pericardial space, directly adjacent to the heart. Implantation above the diaphragm is expected to lead to relatively short surgery time and relatively quick recovery.
The HeartWare's Ventricular Assist System is designed to help a patient's weakened heart pump blood throughout his or her body by removing blood from the left side of the heart and pumping the blood into the aorta (the large blood vessel that carries blood from the heart to the rest of the body). The pump is designed to rest inside the patient's chest. Two small motor stators inside the pump housing cause an impeller within the device to rotate, pumping blood through the system. A driveline (cable) exits the patient's skin and connects the implanted pump to an externally worn controller. The controller is powered by a battery pack, which incorporates two batteries or one battery plus an adaptor connecting to a wall or vehicle electricity outlet. The controller operates the pump and is designed to provide the patient with signals and alarms concerning the operation of the system. The controller and batteries are contained in a carrying case that is designed to be worn either on the patient's belt or over the shoulder.
The HVADTM Pump has only one moving part, the impeller, which spins at rates between 2,000 and 3,000 revolutions per minute. The impeller is suspended within the pump housing through a combination of passive magnets and a hydrodynamic thrust bearing. This 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. There are no mechanical bearings or any points of contact between the impeller and the pump housing.
Device reliability is 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 to help ensure optimal blood flow characteristics. The use of a wide-bladed impeller and clear flow paths through the system are expected to help minimize risk of pump induced hemolysis (damage to blood cells) or thrombus (blood clotting).
People who read this, also read...
back to top