Small pumps that save lives
"This experience has changed my life", reports Michelle Kellim, 33 years old, from Florida. "I have always led a healthy life. I had never once considered that I could suffer from heart disease at my age." The mother of two children used to run five miles every day and had always had a healthy diet. But one night her husband, Erik, woke up next to her and noticed that Michelle had stopped breathing. It was a minimally invasive cardiac pump called Impella® 2.5 that saved Michelle’s life.
Whether in an acute emergency or during a planned operation, so-called haemodynamic instability ("haemodynamic" relates to the movement of blood) is a feared and serious complication which can occur when occluded coronary arteries are opened. The pumps are therefore used both in cardiac surgery during or following operations and also during procedures in cardiac catheter laboratories. Depending on the Impella® model, the pump can support the heart for up to ten days. This gives the heart time to regenerate.
"Our Impella® pumps have already been used over 16,000 times worldwide", explains Ronald Lutz, Marketing Manager of ABIOMED Europe GmbH (Aachen, Germany) which produces these remarkable miniature blood pumps − with components, experience and expertise from FAULHABER. Basically, the Impella® pump mimics the natural cardiovascular system which transports oxygenated blood from the left ventricle through the aortic valve and into the ascending aorta, from where the blood enters the coronary vessels and the systemic circulation. The heart can recover because the Impella® pump actively relieves the strain on the left ventricle. The pump can deliver up to five litres of blood per minute.
Using a guide wire inserted via the femoral artery, the Impella® pump is positioned in the left ventricle and ascending aorta. There the blood is transported through the inlet area via the cannula towards the outlet, following the natural flow direction of the blood. The diameter of just four millimetres (e.g. the Impella® 2.5 model) means that the aortic valve leaflets can fully close around the cannula. The Impella® pump is controlled using an external console which is also used to optimise settings and to monitor the effect of the pump. The preparation time required before the pump can be put into action has in the meantime been reduced to under three minutes. "Patients can be treated without delay, even in acute emergencies", says Lutz.
From a technical viewpoint, the pump drive consists of a brushless, electronically commutated DC-motor with a diameter of just 4 millimetres in the case of the smallest pump (Impella® 2.5) and 6.4 mm in the case of the larger pump (Impella® 5.0) and a stator length of 12 and 18 millimetres respectively. The pumping performance of the heart is supported with a speed of up to 51,000 revolutions per minute. The drive is based on a self-contained coil and essentially consists of a three-phase winding and a bipolar permanent magnet. The position of the rotor is detected by measuring and evaluating the retroactive generator voltage, making Hall sensors unnecessary.
An impressive feature of the motors is their high level of efficiency. The pressure sensors on the larger pump, which are required in the case of positioning inside the ventricles, have a thickness of 300 µm and are positioned in a flat area on the outside of the motor housing. Apart from the compact dimensions and the high reliability, the comparatively favourable cost/performance ratio is another important factor because each Impella® pump can be used only once.
"With the Impella® pump, we are working at the very limits of the possible", stresses Ronald Lutz, ABIOMED Marketing Manager. The demands placed on a medical product used in life-critical situations are extremely high. FAULHABER has been a reliable partner from the very beginning (i.e. since 1998). "There were no "off-the-shelf" motors that we could have used", explains Lutz. "FAULHABER was flexible and prepared to pursue this path with us and, working as a team, to develop the components exactly as we need them. We are extremely happy with the outstanding level of cooperation."
To this day, relentless further development continues to shape the collaboration between ABIOMED and FAULHABER. "This is one of our great strengths", says Jan-Christopher Mohr from FAULHABER who provides support for ABIOMED from the company headquarters in Schönaich (Germany). The development, modification and enhancement of products precisely according to the needs of the customer are all part of the service that FAULHABER offers. "A process such as this can only be successful if there is continuous dialogue", says Mohr. The continuous exchange of information with the customer allows specific requirements to be understood and optimum solutions to be found.