Ann Thorac Surg 2008;86:622-626. doi:10.1016/j.athoracsur.2008.03.009
© 2008 The Society of Thoracic Surgeons
New Technology
Pediatric Experience With the VentrAssist LVAD
Peter N. Ruygrok, MDa,*,
Don S. Esmore, MBBSb,
Peter M. Alison, MBChBa,
Kirsten A. Finucane, MBChBa,
Shay P. McGuinness, MBChBa,
Alastair D. McGeorge, MBChBa,
Justin Negri, MBBSb,
Kylie Jones, RNb,
Helen C. Gibbs, RNa
a New Zealand Heart and Lung Transplant Service, Auckland City Hospital, Auckland, New Zealand
b Heart Transplant Service, The Alfred Hospital, Melbourne, Australia
Accepted for publication March 5, 2008.
* Address correspondence to Dr Ruygrok, Green Lane Cardiovascular Service, Level 3, Auckland City Hospital, Private Bag 92024, Auckland, 1030, New Zealand (Email: pruygrok{at}adhb.govt.nz).
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Abstract
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Purpose: The purpose of this study is to describe the first experience of implanting a new left ventricular assist device in pediatric patients with end-stage heart failure.
Description: In two recent prospective, international, multicenter clinical trials, three children (aged 
16 years) were implanted successfully with the VentrAssist (Ventracor Limited, Chatswood, Australia), a relatively small, novel, continuous flow, third-generation left ventricular assist device.
Evaluation: Despite the patients' disease severity (each child was in extremis at the time of implantation), VentrAssist (Ventracor Limited) implantation enabled each patient to be discharged home from the hospital. All patients survived for more than 1 year. One patient was successfully transplanted and another was bridged to an adequate degree of recovery; unfortunately, the third patient died on postoperative day 375 while waiting for a suitable donor heart. Consistent with the complications associated with left ventricular assist devices in adults, the main complications in these pediatric patients were infection and thromboembolism.
Conclusions: The VentrAssist may provide a major advancement in the management of larger children and adolescents with end-stage heart failure.
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Introduction
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Left ventricular assist devices (LVADs) have become well-established for selected adult patients awaiting heart transplantation [1]. However, size constraints have limited their use in children [2]. There is a pressing need for LVADs suitable for pediatric use and the development of smaller, third-generation LVADs may offer hope to these patients and their families [3]. This report describes the first pediatric experience with a novel, continuous flow, third-generation, implantable LVAD (VentrAssist; Ventracor Limited, Chatswood, Australia).
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Technology
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The 3 pediatric patients (aged 16 years) described in this report participated in prospective, international, clinical trials of the VentrAssist (Ventracor Limited) as either bridge-to-transplant (patients 1, 3) or destination therapy (patient 2). The two trials, described elsewhere [4], received ethics committee approval (November 2004) and informed consent was obtained.
The VentrAssist device has been described in detail previously [4]. The VentrAssist is relatively small (2.5 in), light (10 oz), runs at 1,800 to 3,000 revolutions per minute and has a unique centrifugal pump with noncontact hydrodynamic bearings. Blood is drawn into the VentrAssist through an inflow cannula, attached to the apex of the left ventricle, and returned through an outflow cannula attached to the ascending aorta (Fig 1). A thin percutaneous lead from the pump exits the body in the right upper quadrant. The lead connects to the system controller, which is powered by a rechargeable, nickel metal hydride batteries worn on an external belt or backpack. The controller manages the batteries, which has audible and visible user alarms, and logs and displays system measurements. Blood pump components are hermetically sealed in titanium housing. The sole-moving part, an impeller, comprises four small blades that are embedded with permanent magnets. The blades spin when an electrical current is sequentially switched between three pairs of coils contained within the titanium housing. The impeller is suspended by a thin cushion of blood within the gap of eight hydrodynamic bearings, one on each face of the four blades.
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Fig 1. Illustration of the VentrAssist left ventricular assist device (Ventracor Limited, Chatswood, Australia) in situ showing: (1) retention of the natural heart; (2) inflow cannula delivering blood from the heart to the device; (3) outflow cannula delivering blood from the device to the aorta; (4) drive line from the pump exiting the body at the abdomen; (5) the controller and the batteries, which may be worn on a belt or backpack.
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Technique
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The VentrAssist implantation procedure has been previously described in detail [4]. The pump is implanted through a median sternotomy using conventional cardiopulmonary bypass. The pump "pocket" is formed in the posterior rectus sheath or in a pre-peritoneal position behind the rectus muscle. After coring of the ventricular apex is performed, a 0.4-inch internal diameter silicone inflow cannula with a polyester felt flange is sutured to the apical myocardium. The ventricular anastomosis is completed using horizontal mattress sutures buttressed with Teflon pledgets (Ventracor Limited). The outflow cannula is composed of a 0.4-inch gelatin-impregnated woven Dacron (DuPont, Wilmington, DE) conduit covered by a fenestrated polypropylene tube and is anastomosed to the aorta in a standard end-to-end fashion. The percutaneous lead is tunneled through the subcutaneous fat to exit the body in the right upper quadrant. The lead is secured to the skin using adhesive patches and protected from infection with sterile dressings. Patients are initially managed in an intensive care unit. They are progressively anticoagulated with warfarin (aiming for an international normalized ratio of 2.0 to 3.0) and low-dose acetylsalicylic acid before being discharged from the hospital to home.
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Clinical Experience
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Patient 1
Increasing fatigue and shortness of breath developed in a 10-year-old girl (Table 1) during a 3-month period. A chest roentgenogram demonstrated marked cardiomegaly and an echocardiogram that showed severe biventricular dilatation and impairment. As there was no evidence of myocarditis on cardiac biopsy, the diagnosis of a dilated cardiomyopathy (presumably viral) was made. Her condition deteriorated, despite steroid and immunoglobulin therapy, and she required increasing inotropic support. She had a cardiac arrest from which she was resuscitated, and she had an ongoing requirement for triple inotropic therapy (ie, adrenaline, milrinone, and dobutamine) and mechanical ventilation. Repeat echocardiographic findings were a left ventricular end-diastolic volume of 217 mL, end-systolic volume of 186 mL, ejection fraction of 14%, as well as severe right ventricular dilatation and impairment. Although made more difficult by the patient's small size, a VentrAssist was implanted (Fig 2) and skin closure was achieved. Her initial progress was slow due to poor right ventricular function, but she was extubated on postoperative day 7. She was discharged home on postoperative day 36 and placed onto the transplant waiting list 2 months later. Subsequently, she suffered three episodes of staphylococcal aureus sepsis, which were believed to be caused by an ascending driveline infection. She was treated with intravenous flucloxacillin and vancomycin. The final infectious episode was associated with a severe coagulopathy contributed to by warfarin. After a massive intracerebral bleed, the patient died on postoperative day 375.
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Fig 2. Chest and abdominal roentgenogram of Patient 1 with the VentrAssist left ventricular assist device (Ventracor Limited, Chatswood, Australia) in situ.
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Patient 2
A 16-year-old girl (Table 1) who had been treated with cyclophosphamide, doxorubicin, vincristine, and prednisone for a diffuse B-cell non-Hodgkins lymphoma, presented to her local hospital with increasing abdominal pain and shortness of breath. Presentation occurred 10 weeks after her last dose of chemotherapy and 32 weeks after diagnosis. An echocardiogram showed a severe cardiomyopathy. After transfer to a tertiary hospital, she was intubated and ventilated, and she required increasing inotropic support. Subsequently, she was established on extracorporeal membrane oxygenation support. Her liver and renal function improved and 7 days later she received a VentrAssist as destination therapy with the possibility of considering transplantation after a 1-year period of remission. She was discharged from intensive care on postoperative day 9 and from the hospital on postoperative day 51. Increased pump power consumption (from a baseline of 4.9 to 6.2 watts) occurred on postoperative day 40, which was believed to be caused by a slow deposition of fibrin within the pump, despite therapeutic warfarin and aspirin. The patient was treated with reteplase (5 units) and clopidogrel was added to warfarin and aspirin without sequelae. On postoperative day 188, the patient had a transient left facial droop with slurred speech and visual disturbance; these events were secondary to an embolic stroke, proven by computed tomography, which was associated with a subtherapeutic international normalized ratio of 1.7. She was also hospitalized for two episodes of abdominal pain and vaginal blood loss resulting from a possible ovarian cyst rupture. In addition, a driveline infection required two hospital admissions for intravenous antibiotics. After 1 year of LVAD support she was placed on the transplant waiting list. However, echocardiograms revealed an improvement in left ventricular function (ie, left ventricular end-diastolic dimension of 47 mm, left ventricular end-systolic dimension of 34 mm). The VentrAssist was explanted without complication on postoperative day 377. The patient remains well on postoperative day 911 with an ejection fraction of 40%. She is being treated with perindopril, digoxin, bisoprolol, amiodarone, aspirin, and warfarin.
Patient 3
A 14-year-old boy (Table 1), who was diagnosed with a cardiomyopathy at 6 months of age, experienced a progressive deterioration in cardiac function during childhood. At 12 years of age, after a further acute admission to hospital, he underwent a mitral annuloplasty for severe mitral regurgitation. Despite a good recovery initially, 6 months later worsening heart failure (left ventricular end-diastolic volume 317 mL, left ventricular end systolic volume 276 mL, ejection fraction 14%) developed (Fig 3), and he was accepted onto the transplant waiting list. He required ongoing, inotropic support, and implantation of an LVAD was planned. However, he suffered a cardiac arrest and was established on extracorporeal membrane oxygenation. He awoke 2 days later and was neurologically intact. He was extubated, and 4 days later he received a VentrAssist (Fig 3). He was discharged from the hospital on postoperative day 28. A staphylococcal septicemia, probably from an ascending driveline infection, was treated with 6 weeks of intravenous flucloxacillin, followed by prophylactic oral flucloxacillin. The patient underwent heart transplantation on postoperative day 208, receiving a donor heart from an 18-year-old man who weighed 90 kg (Fig 3). His post-transplant recovery was complicated by a T8 paraplegia, believed to be due to an anterior spinal artery embolus. Circulatory compromise of the spinal arteries after the prolonged period of cardiac massage more than 7 months earlier may have also been a contributing factor. The patient remains paraplegic as of postoperative day 954, but is otherwise well.
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Fig 3. Serial chest and abdominal roentgenograms of Patient 3 showing: (left panel) pre-implant, (middle panel) VentrAssist left ventricular assist device (Ventracor Limited, Chatswood, Australia) in situ, and (right panel) post-transplant.
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Comment
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This is the first description of the clinical outcomes achieved in pediatric patients implanted with a small, novel, continuous flow, third-generation LVAD (VentrAssist). Despite the 3 patients (aged 10, 14, and 16 years) being in extremis at the time of implantation, the VentrAssist enabled each patient to be discharged home from the hospital and all survived for more than 1 year. One patient was successfully transplanted and another was bridged to an adequate degree of recovery; unfortunately, the third patient died while waiting for a suitable donor heart. Although we acknowledge our patients were not free of the complications well-described in adults, namely infection and thromboembolism, the results are encouraging, particularly given the recognized need for smaller LVADs suitable for pediatric use. The VentrAssist may provide a major advancement in the management of larger children and adolescents (body surface area > 1.0 m2) with end-stage heart failure.
The paucity of publications on the use of a third-generation LVAD in pediatric patients limits comparisons with the literature. Nevertheless, the outcomes achieved in our study are encouraging, relative to the results summarized in two major reports on pediatric mechanical support [5, 6]. Based on data from the North American Pediatric Heart Transplant Study, the mean duration of mechanical support in 99 children (mean age, 13.3 years) was 57 days, with 77% surviving to transplantation and 39% requiring biventricular assistance [5]. In a second report, the mean duration of mechanical support in 74 children (mean age, 7.6 years) was 36 days, with 15% being weaned, 43% being transplanted, and 41% dying while awaiting transplantation [6]. In the last 6 years of the 16-year program, 76% were weaned or successfully bridged to transplantation [6]. In comparison with these data, the extended duration of support achieved with the VentrAssist and the successful discharge of all patients auger well for further pediatric implantations. If our results are supported in a larger patient cohort, the VentrAssist could provide opportunities for pediatric patients to optimize their physical condition for transplantation or, on occasion, to facilitate recovery.
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Disclosures and Freedom of Investigation
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The patients described in this report participated in clinical trials sponsored by Ventracor Limited. Ventracor Limited provided the VentrAssist devices and contributed to research nurse salaries. The authors take full responsibility for trial design, methods used, outcome measurements, analysis of data, and production of the written report.
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Acknowledgments
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The authors acknowledge the independent medical writing assistance provided by ProScribe Medical Communications (www.proscribe.com.au) for the final draft of the manuscript. ProScribe's services were funded by Ventracor Limited, Chatswood, Australia, and complied with international guidelines for Good Publication Practice.
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Footnotes
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Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
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References
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- Stevenson LW, Rose EA. Left ventricular assist devices: bridges to transplantation, recovery, and destination for whom? Circulation 2003;108:3059-3063.[Free Full Text]
- Sharma MS, Webber SA, Morell VO, et al. Ventricular assist device support in children and adolescents as a bridge to heart transplantation Ann Thorac Surg 2006;82:926-932.[Abstract/Free Full Text]
- Blume ED, Duncan BW. Pediatric mechanical circulatory supportIn: Frazier OH, Kirklin JK, editors. Mechanical circulatory support. New York, NY: Elsevier; 2006. pp. 127-135.
- Esmore D, Spratt P, Larbalestier R, et al. VentrAssist left ventricular assist device: clinical trial results and clinical development plan update Eur J Cardiothorac Surg 2007;32:735-744.[Abstract/Free Full Text]
- Blume ED, Naftel DC, Bastradi HJ, Duncan BW, Kirklin JK, Webber SA. Outcomes of children bridged to heart transplantation with ventricular assist devices Circulation 2006;113:2313-2319.[Abstract/Free Full Text]
- Potapov EV, Stiller B, Hetzer R. Ventricular assist devices in children: current achievements and future perspectives Pediatric Transplantation 2007;11:241-255.[Medline]
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Abstract
Introduction
