Abstract and Introduction
Due to shortages in donor organ availability, advanced heart-failure patients are at high risk of further decompensation and often death while awaiting transplantation. This shortage has led to the development of effective mechanical circulatory support (MCS). Currently, various implantable ventricular-assist devices (VADs) are able to provide temporary or long-term circulatory support for many end-stage heart-failure patients. Implantation of a total artificial heart (TAH) currently represents the surgical treatment option for patients requiring biventricular MCS as a bridge to transplant (BTT) or destination therapy (DT). However, the clinical applicability of available versions of positive displacement pumps is limited by their size and associated complications. Application of advanced technology is aimed at solving some of these issues, attempting to develop a new generation of smaller and more effective TAHs to suit a wider patient population. Particular targets for improvement include modifications to the biocompatibility of device designs and materials in order to decrease hemorrhagic and thromboembolic complications. Meanwhile, new systems to power implanted driving units which are fully operational without interruption of skin barriers represent a potential means of decreasing the risk of infections. In this review, we will discuss the history of the TAH, its development and clinical application, the implications of the existing technological solutions, published outcomes and the future outlook for TAHs.
Introduction: The Pioneer Trail
Total replacement of the failing heart with a mechanical pump has been the Holy Grail for cardiac surgeons for decades. The early years of heart transplantation and development of an artificial heart represent a fascinating and controversial part of the history of medicine in the last century. Moving forward with artificial cardiac replacement required physicians to break away from the ethical conventions established by others. Initial efforts at creating a complete cardiac replacement artificial organ began as one of the several scientific initiatives during the Kennedy administration in the 1960s. William Kolff and Michael DeBakey were among the pioneers of artificial heart development. During these years, the National Institutes of Health (NIH) were a very important source of funding with grants and contracts for scientists and engineers, becoming a catalyst for artificial heart research. There were at least four academic institutions in the USA with robust research programs working on developing artificial hearts for clinical applications: William Kolff's team at the University of Utah, Michael Debakey's team at the Baylor College of Medicine, William Pierce's team at Pennsylvania State University, and Yuki Nosé's team at the Cleveland Clinic. There were also artificial heart research programs underway in academic centers in Japan, West Germany, East Germany, Czechoslovakia and the Soviet Union. Researchers were working on improving device designs and materials, performance, durability and outcome measures through extensive bench research and animal experiments.
The first human implant took place in 1969 at the Texas Heart Institute in Houston. Denton Cooley implanted a pneumatic Liotta total artificial heart (TAH) as a BTT in 47-year-old patient who could not be weaned from cardiopulmonary bypass. After 64 hours of support with the TAH, the patient underwent cardiac transplantation but eventually died of organ rejection 32 hours later. Many of the scientists at the time thought this operation was premature, but it paved the way for the next clinical era of TAHs. The next human implant took place in 1981. The operation was again performed in Houston, Texas by Dr. Cooley as a BTT. He waited 12 years before re-attempting the implantation of a TAH. This time, Cooley implanted a pneumatic Akutsu TAH. This device was made of an improved synthetic material, polyurethane, but it still inflated by compressed air. The device provided 39 hours of support for the patient, who died shortly after his transplant surgery.
The third human implant was performed in 1982 at the University of Utah by Dr. William DeVries in a 61-year-old patient, Barney Clark. This was the first time that a TAH was implanted as a permanent replacement for a natural heart. The Jarvik 7 TAH, developed in Kolff's lab, was named after Dr. Robert Jarvik, the most recent designer of the device. Clark never left the hospital, as he was tethered to the air compressor with a size of a washing machine, which powered his artificial heart. He experienced various adverse events and eventually died after 112 days of support. Three more patients in the USA and one patient in Sweden were implanted with the Jarvik 7 as a permanent replacement device in 1984 and 1985. The longest survivor was William Schroeder, who lived for 620 days.
Despite the great enthusiasm during the pioneering years, the goal to complete cardiac replacement was too extensive for the level of scientific, clinical and social maturation of the era, and many scientists believed that this was not the technology of the future.
The National Heart Institute decided to end its funding of the technology. The research in the field of MCS was focused on VADs, where remarkable advancements in reliability and miniaturization of devices were achieved in just two decades.
Many research projects on TAH at sites such as Phoenix, Penn State, Berlin, Vienna, Brno, Unger, Poisk-IOM, were stopped after a few clinical implants, mainly due to complications which limited the lifespan of early human recipients to days.
Nevertheless, after the first five successful cases, the Jarvik 7 heart became more widely used as a temporary TAH bridging patients to transplant. Since 1982, more than 1,300 patients have used the Jarvik 7 heart. The company's ownership has changed hands several times and it was eventually renamed as the CardioWest heart. After a 10-year long clinical study involving 95 patients, this TAH produced a 79% success rate for BTT with excellent overall survival, including post-transplantation. In 2004, the FDA granted their approval, making CardioWest the first and still the only fully approved TAH in USA. In 2006, it was CE marked as well.
From the pioneering era to date, only one implantable replacement heart, the AbioCor TAH, received FDA approval in 2006, under the Humanitarian Use Device (HUD) provision for DT. At present, another implantable TAH, the Carmat TAH, has just started a clinical trial in France.
Ann Cardiothorac Surg. 2014;3(6):595-602. © 2014 AME Publishing Company