Journal of Pediatric Cardiology and Cardiac Surgery 3(1): 44‒49 (2019)

Case Report

Successful Management of Short-Term Continuous-Flow
Ventricular Assist Device for a Pediatric Patient:
Report of a Case
Yusuke Yamamoto, MD1), Akinori Hirano, MD, PhD1), Yukihiro Yoshimura, MD, PhD1),
Masatsugu Terada, MD, PhD1), Naofumi Sumitomo, MD2), Masaru Miura, MD, PhD2),
Kensuke Yagi, CE3), Takuji Yoshida, CE3), Takayuki Sueishi, MD4),
Makoto Motomura, MD4), Osamu Saito, MD, PhD4), and Naoki Shimizu, MD, PhD4)
1) Department of Pediatric Cardiovascular Surgery, Tokyo Metropolitan Childrenʼs Medical Center, Tokyo, Japan
2) Department of Pediatric Cardiology, Childrenʼs Medical Center,

Tokyo Metropolitan Childrenʼs Medical Center, Tokyo, Japan

3) Department of Clinical Engineering, Tokyo Metropolitan Childrenʼs Medical Center, Tokyo, Japan

4) Department of Pediatric Intensive Care, Tokyo Metropolitan Childrenʼs Medical Center, Tokyo, Japan

The importance of the short-term continuous-flow ventricular assist device (STCF-VAD) for the management ofpediatric patients with refractory cardiogenic shock is growing along with the increasing use of the Berlin HeartEXCOR pediatric ventricular assist device. Nevertheless, clinical experience with the STCF-VAD for pediatricpatient is insuﬃcient with unsatisfactory outcomes to date, especially in Japan. We report our experience of one
month of successful management of the STCF-VAD in a one-year-old boy of dilated cardiomyopathy. He waspreviously treated with VA-ECMO, and then converted to the STCF-VAD as a bridge to the EXCOR. Although
six times of circuit exchanges were required due to thrombus formation, the patients experienced no complication and finally converted to the EXCOR after 29 days of STCF-VAD support. Our experience suggests that
adequate antithrombotic therapy to reduce the risk of both thrombogenesis and hemorrhagic complications,frequent assessment of the circuit to detect thrombi as early as possible, and prompt circuit exchange in case of
a floating or growing thrombus are the key to preventing adverse events. Application of percutaneous cannulae
exclusively for the EXCOR might also be advantageous for prevention of thrombogenesis and elimination of
re-open chest surgery at the transition to the EXCOR. The STCF-VAD therapy requires highly strict management, and therefore should be managed by an experienced medical team.

Keywords: short-term, continuous-flow, ventricular assist device, pediatric patients, bridge to bridge
therapy

Introduction
Although the Berlin Heart EXCOR pediatric ventricular assist device has greatly improved the managementof pediatric patients with severe heart failure, its application is strictly limited in Japan, with only six institutes
given the permission of implantation of the device.
Therefore, alternative types of mechanical circulatory

support are indispensable in case of acute circulatory
failure in such patients. Veno-arterial extracorporeal
membrane oxygenation (VA-ECMO) is the preferredchoice for first-line support, while their safe durationis relatively short. The short-term continuous-flow
ventricular assist device (STCF-VAD) not only allows
longer management than VA-ECMO, but also serves as abridge to more durable device. We experienced success-Received: October 25, 2018; Accepted: January 7, 2019
Corresponding author: Yusuke Yamamoto, MD, Department of Pediatric Cardiovascular Surgery, Tokyo Metropolitan Childrenʼs
Medical Center, 2‒8‒29 Musashidai, Fuchu-shi, Tokyo 184‒8561, Japan
E-mail: acamais@gmail.com
doi: 10.24509/jpccs.190108© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

45

ful management of STCF-VAD for about one month ina pediatric patient with dilated cardiomyopathy (DCM).
There are only a few reports describing clinical experiences of STCF-VAD in Japan,1) and the reported results
are not satisfactory mainly due to high incidence ofcomplication such as major bleeding, neurological disorder, and infection. Herein, we describe our experience
focusing on prevention of complications and the safe
management of STCF-VAD.

Case Presentation
A seven-month-old previously healthy boy was transferred to our hospital with acute circulatory collapse due
to severe heart failure. VA-ECMO support was immediately commenced via the right cervical approach, andthen he was diagnosed with DCM. After 12 days of support, he was recovered and weaned from the VA-ECMO.
Consultation with the University of Tokyo Hospital,
which is one of the four facilities in Japan certified forpediatric heart transplant, indicated that he was a candidate for heart transplant. Although rigorous medical
therapy was initiated, he developed circulatory collapse
requiring cardiopulmonary resuscitation when he waseleven months old and VA-ECMO support was emergently established again via a median sternotomy. Conversion to the EXCOR was not indicated at this point
because of two concerns that might have led him out of
indication of heart transplant: possibility of neurologicaldeficits following cardiopulmonary resuscitation andsevere respiratory failure due to left bronchial obstruction secondary to compression by the dilated heart.
Hence, we decided to assess his condition and judge
the indication for heart transplant after converting to
the STCF-VAD.
After 24 days of VA-ECMO support which was spentfor neurological assessment, preparation of devices for
the STCF-VAD, and inspection tour to University ofTokyo Hospital by our team, surgery was undertaken toconvert to STCF-VAD when he was twelve months old
and his body weight was 7.1 kg. Via a median approach,the VA-ECMO was removed after establishment ofcardiopulmonary bypass and a 6-mm straight EXCOR
Apex cannula (C18A-020; Berlin Heart AG, Berlin,
Germany) was inserted into the apex of the left ventricle. A 10-mm expanded polytetrafluoroethylene graft(STRETCH Vascular Graft, W.L. Gore & Associates, Inc.,
Flagstaﬀ, AZ, USA) was anastomosed in an end-to-side

fashion to the ascending aorta, following which a 6-mm
angled EXCOR Arterial cannula (C80G-021; Berlin
Heart AG, Berlin, Germany) was inserted into the graft.
The distal ends of the two cannulae were led outside thebody through the rectus sheath and connected to thecircuit of STCF-VAD. Our original STCF-VAD system
consists of a ROTAFLOW centrifugal pump (BO-RF32;
Maque, Rastatt, Germany) and a polyvinylchloride
circuit with the T-NCVC® heparin coating (National
Cardiovascular Center and TOYOBO, Osaka, Japan).2)
Following the administration of catecholamines andinhaled nitric oxide (iNO) as support for the right ventricle (RV), weaning from cardiopulmonary bypass andconversion to STCF-VAD was performed uneventfully.
The patientʼs postoperative course was stable. Administration of iNO and catecholamine were terminatedin postoperative day three and nine, respectively(Fig. 1). Unfractionated heparin (UFH) administration
was started 12 hours after operation, targeting an activated partial thromboplastin time of 40‒60 seconds.
Aspirin (5 mg/kg/day) and dipyridamole (4 mg/kg/day)were administered from day three and four of STCF-VAD
support, respectively. Warfarinization was started on day
six, targeting a prothrombin time international normalized ratio (PT-INR) between 2.5 and 3.0, and wasaccompanied by UFH administration until the warfarindose reached a therapeutic range (Fig. 2). Althougha total of six circuit exchanges were required due tothrombus formation, there were no neurological complications, no hemorrhagic events, and no major infections
throughout the clinical course. Intravenous injection of
sedative drugs were ceased by the day 13 of STCF-VAD
support, and since then, small dosage of internallyadministrated phenobalbital and chlorpromazine wereenough for safe management of the patient in theintensive care unit. Electroencephalograph finding was
normal and the Glasgow coma scale of the patient was
E4VTM4 without any paralysis. In addition, respiratory
function was suﬃcient for extubation. Then, conversion
to the EXCOR was indicated.
The patient was transferred to the University of Tokyo
Hospital after 29 days of STCF-VAD support, and on
the same day the extracorporeal drive unit was changed
from the centrifugal pump to the EXCOR. After 9months of EXCOR support, he underwent heart transplant at the same hospital when he was one year andeleven months old and his body weight was 11.8 kg, and© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

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Fig. 1 Details of the management of the patient
The upper part of the ﬁgure indicates the cardiovascular agents administered during the course of treatment. The middle part indicates the transition of hemodynamic parameters relevant to STCF-VAD management. The timing of circuitexchange is also illustrated in the lower part of the ﬁgure. CVP, central venous pressure; DOB, dobutamine; Epi, epinephrine;
iNO, inhaled nitric oxide; MIL, milrinone; SNP, sodium nitroprusside; VAD, ventricular assist device

Fig. 2 Details of antithrombotic therapy and the resultant thrombus formation in the circuit
The upper part of the ﬁgure indicates the doses of antithrombotic agents used. The middle part indicates the transition ofblood coagulability as a measure of antithrombotic therapy. The lower part indicates the average number of ﬂoating thrombi
detected in the circuit per observation, along with the transition of serum LDH levels. aPTT, activated partial thromboplastin
time; LDH, lactate dehydrogenase; PT-INR, prothrombin time international normalized ratio; UFH, unfractionated heparin

J Pediatr Cardiol Card Surg Vol. 3, No. 1 (2019)47

was back to home in stable condition about two months
after operation.

Discussion
Along with the increasing use of the EXCOR,STCF-VAD has gained importance in the management
strategy of severe heart failure in pediatric patients.
STCF-VAD is more advantageous than VA-ECMO inthat it enables longer continuation and more eﬃcientvolume unloading of the left ventricle. In addition, as
patients on VA-ECMO support are thought to be atrisk of postoperative RV failure after LVAD implantation,3) it is worthwhile to assess RV function and judge
the indications of LVAD implantation after conversion
to STCF-VAD. From the reported results, 65‒71% of
patients who underwent STCF-VAD support subsequently had positive courses, such as recovery, hearttransplant, or conversion to durable VAD devices.4, 5)Morbidity due to major adverse events was reported asfollows: major bleeding in 24‒29%, neurological disorders in 15‒24%, and infections in 17%,4, 5) with themedian duration of the STCF-VAD support in 12‒15
days. Prevention of these adverse events is essential for
improving the outcomes of STCF-VAD management.
Thromboembolic stroke and intracranial hemorrhage
are two major causes of the neurological disorders. UFH,
aspirin, dipyridamole, and warfarin were included inantithrombotic therapy for STCF-VAD, referring to the
Edmonton antithrombotic guidelines for the EXCOR.6)
UFH administration is recommended to started at least
24 hours after operation in the current guidelines,7)
although we had to start it 12 hours after operation due
to early thrombus formation within the circuit. From
our experience, a low PT-INR (<1.5) seems to be relevant to thrombus formation within the circuit (Fig. 2).
Assessment of aspirin resistance and necessary increasein the dose should be taken into consideration in case ofrecurrent thrombus formation.7, 8) As for hemorrhagic
complications, complete reversal of UFH and strict control of blood pressure (targeted mean BP <70 mmHg)
are thought to be important in the early postoperative
period.9) Mean blood pressure also should be controlled
above 50 mmHg to maintain adequate perfusion of vitalorgans.
In addition, plasma fibrinogen and platelet levels were
kept above 200 mg/dL and 100,000/µL), respectively.
Plasma antithrombin level were also kept over 70% toachieve suﬃcient antithrombotic eﬀects with a minimum dose of UFH, which may prevent hemorrhagic
complications due to excessive UFH administration.10)
Assessment and treatment of thrombus formed in
the circuit is crucial for prevention of thromboembolic
complications. In our strategy, visual inspection of thecircuit was performed every 2 hours, and a mobile andgrowing thrombus was regarded as a possible cause ofthromboembolism, while a stable thrombus was considered to be harmless. Thrombolysis was not performedon account of the lack of evidence regarding its safety
and eﬃcacy in pediatric populations. In concordancewith previous reports suggesting the eﬃcacy of monitoring serum levels of lactate dehydrogenase (LDH) for the
early detection of thrombus,11) it was speculated fromour experience that abrupt elevation of LDH to over
500 IU/L may indicate increased thrombus formation(Fig. 2). Plasma-free hemoglobin may also be an indicator of thrombus formation.12)
The components of the STCF-VAD circuit could be apotential source of thrombogenesis. Daily observation
indicated that mobile thrombi tended to be formed on
the infusion side of the circuit rather than the drainage
side, while they were scarcely found in the centrifugal
pump (Fig. 3), as a previous study has already reported.5)
Compared with pulsatile flow, continuous flow has beenshown to have a tendency for stagnation of blood flow atsites of abrupt enlargement of flow caliber.13) Therefore,
the circuit must be designed with as less caliber changes
as possible. The centrifugal pump, which has connecting
ports with diameter of 10 mm, was connected to themain tube with diameter of 6 mm via a tapering tube
to create a gradual change in caliber. In addition, we
adopted the percutaneous cannulae exclusively for the
EXCOR with the permission by both the ethics board of
our institute and the Japanese Association for Clinical
Ventricular Assist Systems (JACVAS). In the application
for JACVAS, no additional qualification was requiredon the condition that implantation of the cannulae
should be performed under the instruction of the staﬀ
of University of Tokyo Hospital. Except for the concern
about the high cost which was necessitated due to out of
insurance support, application of the EXCOR cannulae
was thought to be advantageous not only because theymight be less thrombogenic than other cannulae for cardiopulmonary bypass which were not designed for a log
time of use, but also because it enables transition to the© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

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Fig. 3 Conﬁguration of STCF-VAD circuit and the thrombus detection rate in the circuit
The upper part of the ﬁgure shows the conﬁguration of the STCF-VAD circuit. The main tube has a lateral branch for convenient de-airing of the circuit during circuit exchange. The lower part indicates the thrombus detection rate, i.e. the cumulative number of thrombi detected per total number of inspections (=284), for both ﬁxed and mobile thrombi. STCF-VAD:
short-term continuous-ﬂow venticular assist device

EXCOR without re-open chest surgery.
For infection prophylaxis, antimicrobial agents wereadministered according to the standard regimen forpatients under mechanical circulatory support, withnecessary escalation considering the results of culture
tests. In addition, insertion sites of percutaneous cannulae, where surgical site infection frequently occurs, were
prophylactically dressed with the silver-containing carboxymethylated cellulose (AQUACEL Ag®, ConvaTec,
Princeton, NJ, USA), which is supposed to absorb the
exudate along with gradual release of silver ions, allowing moist wound healing concomitant with antimicrobial eﬀects.14)
Management of STCF-VAD flow was based on theconcept that cardiac output is regulated primarily by
the RV function and VAD flow must be adjusted to it.
As a daily practice, the revolutions per minute of thecentrifugal pump were adjusted to keep the adequate LV
volume by observing the shape of interventricular septum with echocardiography. In addition, central venous
pressure was thought to be the most relevant parameterof RV function. During the early postoperative period,
catecholamines and iNO were administered not only
to prevent RV failure, but also to achieve maximum
RV output to keep the STCF-VAD flow high, with the
J Pediatr Cardiol Card Surg Vol. 3, No. 1 (2019)intention of supporting visceral recovery and reducing
the risk of thrombus formation (Fig. 1). After the acuteperiod, flow was gradually decreased along with tapering of RV support.
The STCF-VAD should be converted to the EXCOR assoon as possible because of it's high incidence of complication. Although we have confirmed the will of parents
for heart transplant in advance, 29 days of STCF-VAD
management was necessary in the present case mainly
to wait the decision-making of parents to implant the
EXCOR. In this process, discussion between parents andthe pediatrician of University of Tokyo Hospital who
specializes heart transplant was thought to be crucial torelieve the anxiety of the parents and to confirm theirdecision. Thus it can be said that one key to prevent thelengthening of STCF-VAD management is frequent andenough explanation to the parents by the expert of hearttransplant.

Conclusion
We have to realize the growing importance of the
STCF-VAD as a bridge to EXCOR for pediatric patientswith severe heart failure on VA-ECMO support, especially in the institute without the permission to use
EXCOR,

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As the STCF-VAD therapy requires highly strict management, it should be managed in institutes with enoughexperience of ECMO therapy and by an experienced
medical team which consists of intensive care doctors
and nurses, clinical engineers, cardiovascular surgeons,and infection control doctors. Far more clinical experience and improvement in the devices are necessary to
improve the clinical outcomes of the STCF-VAD.
Acknowledgment
The authors are grateful to Dr. Yasutaka Hirata (Department of Cardiovascular Surgery, University of Tokyo) for somany valuable instructions and advice.
Conﬂicts of Interest
All authors declare that there is no conflict of interest.

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