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Department of Artificial Organs

Members

Director Eisuke Tatsumi
Laboratory chiefs Yoshiaki Takewa, Tomonori Tsukiya, Toshihide Mizuno
Research staff Daichi Akiyama
Research fellows Kei Iizuka, Daisuke Takeshita, Nobumasa Katagiri, Hideyuki Kakuta, Takeshi Terazawa
Visiting researcher Tomohiro Nishinaka, Takashi Nishimura

Research activities

Development of Totally Implantable Artificial Heart System

The heart transplantation is in widely available use in Western countries, but there is a serious shortage of donor hearts. Under this situation, demands on heart replacement by an artificial heart have grown tremendously. Our research group is now developing a total artificial heart system which can be fit to a recipient of small physique. We have newly developed an implantable electrohydraulic actuator, which can be placed separately from the blood pumps, and this TAH system was successfully implanted in the chronic animal experiment for the first time in Japan. We achieved the longest survival of 85 days in an animal experiment, which is the longest record in Japan. We have been continuously improving the system in various aspects, such as its pumping performance, the anatomical fit, suppression of surface temperature. Apart from the pumping unit, we have also developing the transcutaneous energy transmission system. The system has demonstrated high transmission efficiency in a chronic animal testing. Implantable secondary battery, transcutaneous optical telemetry system, and implantable small controller are now being developed to realize the totally implantable artificial heart system. We have recently succeeded the first implantation of the whole system in an animal testing. Controlling method of an artificial heart, which enables appropriate response of pumping condition to circulation changes using some vital signs as blood oxygen consumption, is studied by treadmill exercise tests.

<Recent publications>
  1. Tatsumi E, Taenaka Y, Uesho K, Homma A, Nishinaka T, Kakuta Y, Tsukiya T, Takano H, Masuzawa T, Nakamura M, Koshiji K, Fukui Y, Tsukahara K, Tsuchimoto K, Wakui H, Current status of development and in vivo evaluation of the National Cardiovascular Center electrohydraulic total artificial heart system: 2000, Journal of Artificial Organs, Vol. 3, pp. 62-69.
  2. Tatsumi E, Masuzawa T, Nakamura M, Taenaka Y, Nishimura T, Endo S, Zhang B, Kakuta Y, Nakata M, Makamura T, Nishinaka T, Takano H, Tsukahara K, Tsuchimoto K, In vivo evaluation of the National Cardiovascular Center electrohydraulic total artificial heart: 1999, Artificial Organs, Vol. 23, No. 3, pp. 242-248.

Development of Pneumatic Total Artificial Heart

We have also been developing an air-pressure-driven total artificial heart system (Pneumatic Total Artificial Heart, PTAH) for heart replacement of end-stage heart disease patients. The PTAH system is comprised of left and right pulsatile blood pumps, an extracorporeal console unit and drivelines connecting the pumps and the console. The blood pumps are actuated by air pressure from the console unit through the drivelines. The blood pumps are orthotopically installed in the pericardial space after complete resection of the native ventricles, and then the pumps are connected to the native atria, aorta, and pulmonary trunk. Other PTAH systems, including Jarvic 7 or its succeeding type PTAHs, have been implanted in human patients in several western countries. They are currently used for bridge to heart transplantation with satisfactory results. These systems, however, seem too bulky to be implanted into pericardial space of people with standard physique because they were originally designed for the people with large physique. Our PTAH system has demonstrated so excellent anatomical fit that it is implantable in an adult patient weighing about 40 kg.

<Recent publications>
  1. Taenaka Y, Takano H, Noda H, Kinoshita M, Yagura A, Sekii H, Sasaki E, Akutsu T, Design and evaluation of a total artificial heart for patients with a smaller chest cavity: Artificial Organs, Vol. 14, No. 4, pp. 45-47.

Development of Rotary Blood Pumps

Displacement type blood pumps have shown superior capability to maintain the circulation and sufficient durability. Regardless of these advantages, several problems remain to be solved, including its large size and high cost. Rotary blood pumps possess the potential to solve these problems owing to their small size and low cost. We are developing an efficient ventricular assist system consisting of a rotary blood pump by improving its biocompatibility and durability.

So far, we have improved the basic design and hydrodynamic performance in order to enhance the antithrombogenecity, durability, and least damage to the blood components. Consequently, we achieved the continuous driving of 381 days in a chronic animal experiment as an extracorporeal left ventricular assist device. Currently, we are developing an implantable ventricular assist system consisting of implantable centrifugal pumps. The latest prototype was less than half of the former prototype in size and weight. The small power consumption of this system will enlarge the period in which the pump is driven by the implanted battery system, which will significantly enhance the quality of the patient.

<Recent publications>
  1. Wakisaka Y, Taenaka Y, Chikanari K, Okuzono Y, Nishimura T, Endo S, Nakatani T, Takano H, Intrathoracic and intraabdominal wall implantation of a centrifugal blood pump for circulatory assist: 1998, Artificial Organs, Vol. 22, No. 6, pp. 493-497.
  2. Taenaka Y, Wakisaka Y, Masuzawa T, Tatsumi E, Toda K, Miyazaki K, Eya K, Baba Y, Nakatani T, Ohno T, Nishimura T, Takano H, Development of a centrifugal pump with improved antithrombogenicity and hemolytic property for chronic circulatory support: 1996, Artificial Organs, Vol. 20, No. 6, pp. 491-496.

Development of Cardiopulmonary Bypass System for Long-term Use

We investigate the possibility of and develop therapeutic options of cardiopulmonary support with a heart-lung assist device, such as percutaneous cardiopulmonary support and extracorporeal membrane oxygenation in treating patients with life-threatening circulatory and/or respiratory failure.

An integrated artificial heart-lung device has been developed as a long-term cardiopulmonary support system in respect of antithrombogenecity and durability. In particular, integration of a blood pump and artificial lung, employment of a special hollow fiber membrane, and heparin bonding surface treatment displaying excellent thromboresistance, provides several advantages including the marked reduction in the size of the apparatus and the preservation of the gas exchange function within a sufficient level. The possibility of therapeutic options has been investigated from the viewpoint of native lung metabolism.

<Recent publications>
  1. Tatsumi E, Takewa Y, Akagi H, Taenaka Y, Eya K, Nakatani T, Baba Y, Masuzawa T, Wakisaka Y, Toda K, Miyazaki K, Nishimura T, Ohno T, Takano H, Development of an integrated artificial heart-lung device for long-term cardiopulmonary support: ASAIO Journal, Vol.42, No.5, pp. M827-M832.
  2. Tatsumi E, Takano H, Taenaka Y, Nishimura T, Kakuta Y, Nakata M, Tsukiya T, Nishinaka T, Development of an ultracompact integrated heart-lung device: Artificial Organs, Vol. 23, No.6, pp. 518-523.

Physiological Study of Assisted Circulation

Assisted circulation with an artificial heart and an oxygenator not only accompanies interactions between artificial devices and living tissue, but also creates novel conditions of circulation. This aspect of assisted circulation is utilized for investigation of physiological mechanism. We have conducted studies on various fields, including coagulation system, endocrine system, hormonal and nervous control systems of the circulations, peripheral circulation system, morphological changes in cardiovascular systems, and circadian rhythm. Our achievements of the study on physiology of nonpulsatile systemic and pulmonary circulation using chronic animal experiments have been widely paid attention worldwide. We also contributed to the advance in basic medical science concerning the metabolic function of the pulmonary vasoreactive substances by quantitative analysis of the effect of pulmonary artery blood flow on the concentration of the regulating factors.

<Recent publications>
  1. Nishinaka T, Tatsumi E, Nishimura T, Taenaka Y, Imada K, Takano H, Koyanagi H, Effects of reduced pulse pressure to the cerebral metabolism during prolonged nonpulsatile left heart bypass: 2000, Artificial Organs, Vol. 24, No. 8, pp. 676-679.
  2. Nishimura T, Tatsumi E, Taenaka Y, Nishinaka T, Nakatani T, Masuzawa T, Nakata M, Nakamura M, Endo S, Takano H, Effects of long-term nonpulsatile left heart bypass on the mechanical properties of the aortic wall: 1999, ASAIO Journal, Vol.45, No. 5, pp. 455-459.

Development of Ventricular Assist System

We developed the extracorporeal ventricular assist device (VAD) for patients in severe heart failure with acute myocardial infarction and postcardiotomy, which exhibited superior antithrombogenicity and durability. The VAD for infant patients was also developed for the first time in the world. We improved the quality of the devices through sufficient chronic animal experiments before their clinical application. The device we developed successfully passed the clinical trials, and it was approved by the government. The therapy using this device is now approved to be covered by health insurance.

<Recent publications>
  1. Taenaka Y, Takano H, Noda H, Kinoshita M, Tatsumi E, Yagura A, Sekii H, Sakaki E, Akutsu T, Experimental evaluations and clinical applications of a pediatric ventricular assist device (VAD): 1989, Transactions of American Society of Artificial Internal Organs, Vol. 35, pp. 606-608.
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