Ann Thorac Surg 2007;83:1181-1183
© 2007 The Society of Thoracic Surgeons
Case Reports
Successful Use of the Toyobo Left Ventricular Assist Device in a 16-kg Girl Awaiting Cardiac Transplantation
Ayumu Masuoka, MD*,
Toshiyuki Katogi, MD,
Haruhiko Asano, MD,
Mika Iwazaki, MD,
Takahiro Matsuoka, MD,
Motonobu Nishimura, MD,
Shunei Kyo, MD
Department of Cardiovascular Surgery, Saitama Medical School, Saitama, Japan
Accepted for publication July 10, 2006.
* Address correspondence to Dr Masuyoka, Saitama Medical School, Cardiovascular Surgery, Morohongo 38, Moroyama-machi, Iruma-gun, Saitama, Japan (Email: masuoka{at}saitama-med.ac.jp).
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Abstract
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In Japan, no mechanical circulatory support is available for children. We report a case of terminal stage cardiac failure in a 16-kg girl who was implanted with an adult-sized Toyobo-NCVC left ventricular assist device (Toyobo-National Cardiovascular Center, Osaka, Japan) in our unit. She successfully underwent heart transplantation in the United States 5 months later.
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Introduction
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Options available in Japan to support terminal stage cardiac failure are limited. Pediatric pulsatile ventricular assist devices (VAD), such as the Berlin Heart (Berlin Heart AG, Berlin, Germany) and the Medos VAD (Medos Medizintechnik AG, Stolberg, Germany), have not been available in Japan. The literature also describes the more limited use of other adult-type devices in the pediatric population, such as the Japanese Toyobo-NCVC system (Toyobo-National Cardiovascular Center, Osaka, Japan), Abiomed system (Abiomed Inc, Danvers, Calif), Thoratec VAD (Thoratec Corp, Pleasanton, Calif), and the HeartMate system (Thoratec Corp). We report a child who underwent univentricular support with the Toyobo-NCVC left ventricular assist device (LVAD) as a bridge to transplantation. We detail the clinical course, operative modifications, pump settings, and complications that occurred in this child.
End-stage heart failure developed in a 6-year-old girl (height, 111 cm; body weight, 16.2 kg; body surface area, 0.71 m2) who was first noted to have general fatigue 2 years ago. She was diagnosed with dilated cardiomyopathy and received vigorous medical therapy, but her cardiac function continued to worsen. Her parents had already started to raise funds for a heart transplantation overseas and made an informal agreement with a foreign heart center to perform the heart transplantation procedure. Despite a large infusion of catecholamine and mechanical respiratory support, the patient fell into a state of cardiogenic shock. She was transferred to us from a referring hospital with pulmonary edema and extremely low cardiac output (Fig 1). At the time of admission, echocardiography demonstrated a left ventricular ejection fraction of less than 0.15.
Although she weighed only 16 kg, an adult-sized Toyobo-NCVC LVAD (Toyobo, Osaka, Japan) was immediately inserted in the left ventricle using an apical inflow cannula. The ascending aorta of this patient was smaller than the graft of pump outflow, which required a technically difficult end-to-side anastomosis with a side-biting clamp (Fig 2). The patient’s immediate postoperative status was satisfactory because of the sufficient cardiac output supplied by the left ventricular assist device. The only problem was difficult-to-treat hypertension owing to excessive stroke volume induced by the LVAD. The driving mode of the LVAD was set at a stroke rate of 110 per minute and %systole to 35% to control hypertension by reducing stroke volume of the LVAD [1–3].
Anticoagulation therapy was started with a heparin injection on the first postoperative day, and oral Coumadin (Bristol-Myers Squibb, Princeton, NJ) and aspirin administration followed. On the tenth postoperative day, she showed aphasia and hemiparesis, and a computed tomography scan confirmed a cerebral embolism. A fresh thrombosis was found in the pumping chamber, which was immediately exchanged under a short period of simple clamp of the cannulae. After this episode, we changed the driving mode to the "full fill" and "full empty" mode. We speculated that reducing the stroke volume of the pump caused stagnation of the bloodstream in the pumping chamber, which lead to thrombus formation. To pump out almost all the blood in the pumping chamber in each stroke, the stroke volume of this pump needed to be more than 60 mL. As a consequence, the stroke rate had to be decreased to less than 50 per minute and %systole set to 50%.
Hypertension became more prominent after this change in the driving mode, and aggressive administration of antihypertensive therapy was needed. Nitroglycerin, a ß-blocking agent, an angiotensin converting enzyme inhibitor, and a calcium antagonist were used for this 6-year-old patient. No neurologic problems occurred thereafter, although an exchange of the pumping chamber was needed due to fever and a high inflammatory score. She was transported to the United States and underwent a successful heart transplantation 5 months after the beginning of mechanical support. Although a slight neurologic deficit still exists, the patient is doing well 10 months after heart transplantation, without any signs of cardiac failure.
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Comment
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Although severe heart failure is less common among the pediatric population than in adults, end-stage cardiac failure develops in many pediatric patients. For such patients, heart transplantation is the only hope of survival; however, heart transplantation in children is almost impossible in Japan, because Japanese law restricts the age of the organ donor to be older than 15 years. At present, only children from families with enough financial resources or who have successfully raised enough funds can travel overseas to undergo transplantation. Traveling overseas is difficult for patients with terminal-stage heart failure who require heart transplantation, and some patients cannot travel without mechanical circulatory support. In Japan, however, no pump is currently available for use in children over an extended period [4, 5]. Consequently, a pump that has been designed for adults is often used in children [6].
Some problems occur when adult-sized devices are used in children weighing less than 30 kg. First, the ascending aorta is smaller than the graft of the pump outflow, which requires a technically difficult anastomosis. Second, the large sizes of the outflow and inflow tubes are difficult to place in the small space of a child’s subcostal area. Third, the oversized pump causes difficult-to-treat hypertension in these small patients [1–3]. Finally, anticoagulant therapy is sometimes unstable and more difficult to administer in children than in adults. Because of the difficulty in controlling hypertension and in stabilizing anticoagulation therapy [7], this patient sustained a cerebral embolism. However, a change in the pump settings to "full fill" and "full empty" mode, and meticulous control of anticoagulation therapy, allowed her to undergo heart transplantation overseas with no additional thromboembolism episodes.
Even if the law in Japan changed to allow transplantation in children younger than 15 years, only about three heart transplantations are performed each year by harvesting hearts from brain-dead adults in whom the size of the heart does not markedly differ; thus, it is unclear how long children, among whom heart size varies considerably, would have to wait.
Pediatric patients awaiting heart transplantation should be supported by mechanical assist devices for long as needed [4, 5]. Therefore, technical advances in assistive devices designed for children represent an urgent problem in Japan.
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References
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- Copeland JG, Arabia FA, Smith RG. Bridge to transplantation with a Thoratec left ventricular assist device in a 17-kg child Ann Thorac Surg 2001;71:1003-1004.[Abstract/Free Full Text]
- Suri RM, Daly RC, Dearani JA, McGregor CG. Successful use of Thoratec biventricular support in a small child awaiting cardiac transplantation Ann Thorac Surg 2005;80:1920-1922.[Abstract/Free Full Text]
- Matsuwaka R, Matsuda H, Kaneko M, et al. Overseas transport of a patient with an extracorporeal left ventricular assist device Ann Thorac Surg 1995;59:522-523.[Abstract/Free Full Text]
- Fukushima N, Sawa Y, Ichikawa H. Surgical strategies for children with end-stage cardiomyopathy in Japan Pediatr Cardiol Cardiac Surg 2005;21:459-464.
- Kyo S, Nishimura M, Asano H. Ventricular assist system Kyobu Geka 2003;56:61-70.[Medline]
- Stiller B, Weng Y, Hubler M, Lemmer J. Pneumatic pulsatile ventricular assist devices in children under 1 year of age Eur J Cardiothorac Surg 2005;28:234-239.[Abstract/Free Full Text]
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Abstract
Introduction
