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Cardiac Assist Devices: From Emergency Procedures to Regained Quality of Life

For many decades man has had the intention to support or replace the human heart with a mechanical pump to maintain sufficient circulation in patients with severe heart disease. When the first mechanical blood pump was successfully applied in a 36-year old patient (Houston, 1966) as a life saving procedure, a very dynamic evolution for the development of different blood pumps for cardiac support began. In these early days of advanced cardiac surgery the application of those pumps was only performed in life threatening situations since the risk of technical and surgical failure with this new technology was immense. It was essential to provide pulsatile flow patterns to mimic the pulsatility of the natural heart. Mainly pneumatically driven membrane pumps were used in this early period. All pumps were placed extra corporally and were connected to huge, bulky driving units. Patients were kept sedated and immobilized at the ICU-units while on support. Primary indication for placing patients on mechanical cardiac support was “bridge to recovery” for postcardiotomy low cardiac output syndrome and in case of incurable heart disease complete replacement with a totally implantable artificial heart was favoured. With the clinical establishment of orthotopic heart transplantation in the 1970s and early 1980s a further indication came up with mechanical “bridge to transplantation” in patients who were suffering from an acute therapy-refractory hemodynamic deterioration while on the waiting list. In this cohort of patients it turned out that mainly the left ventricle fails and with the support of only one ventricle, patients could be stabilized and implantation procedure was then less traumatic. Due to the high risk of technical failure of these early pumps and the imperfect knowledge of postoperative management of patients, the initial intention of early “bridge to recovery” concepts was to keep patients for a short period on mechanical cardiac support and to wean them as soon as possible. Thrombogenicity of these pumps was a major concern and anticoagulation protocols were investigated. With the new concept of “bridge to transplantation” patients had to be on pump support for longer periods of time and for the first time quality of life issues for these patients came up. To satisfy these new demands, concepts for implantable pumps were developed with the intention of reducing infection and improving mobility. Since excessive miniaturization of pneumatic driving units seemed to be technically unrealistic the concept of electromagnetic driven pumps with the option of small, battery operated, and wearable controllers was investigated. These sac-type pumps were rather bulky and energy supply was performed through a percutaneous drive-/ ventline exiting the skin on the right