Ann Thorac Surg 2006;81:1118-1121
© 2006 The Society of Thoracic Surgeons
Case report
Bridge to Transplant Using the MicroMed DeBakey Ventricular Assist Device in a Child with Idiopathic Dilated Cardiomyopathy
Massimo A. Padalino, MD,
Richard G. Ohye, MD,
Andrew C. Chang, MD,
Robert J. Gajarski, MD,
Edward L. Bove, MD,
Eric J. Devaney, MD
*
Section of Cardiac Surgery, Division of Pediatric Cardiovascular Surgery, and Division of Pediatric Cardiology, University of Michigan School of Medicine, Ann Arbor, Michigan
Accepted for publication January 17, 2005.
* Address correspondence to Dr Devaney, Division of Pediatric Cardiovascular Surgery, University of Michigan Health System, F7830 Mott Hospital, 1500 E Medical Ctr Dr, Ann Arbor, MI 48109 (Email: edevaney{at}med.umich.edu).
 |
Abstract
|
|---|
We report the implantation of the MicroMed DeBakey left ventricular assist device (MDBVAD) in a 10-year-old girl with cardiogenic shock secondary to an idiopathic dilated cardiomyopathy. This was the first pediatric implant of the MDBVAD in the United States and the youngest patient worldwide. The patient recovered well and subsequently underwent successful heart transplantation after 84 days of support.
|
Introduction
|
|---|
The use of mechanical circulatory support in the pediatric population is evolving. Extracorporeal membrane oxygenation (ECMO) is currently the most common form of circulatory support for pediatric patients. Despite its many advantages, ECMO cannot reliably provide long-term support, is fraught with complications, and requires continuous monitoring in an intensive care unit environment. In the adult population, left ventricular assist devices (LVADs) have been shown to provide long-term support both as a bridge to transplantation and as destination therapy [1, 2]. Until recently, all implantable LVADs have been too large for use in children. The development of axial flow devices has allowed for more compact designs. Recently, encouraging preliminary results have been reported with the MicroMed DeBakey ventricular assist device (MDBVAD; MicroMed Technology Inc, Houston, TX) in adults with severe heart failure [3, 4]. We report the first pediatric implantation of the MDBVAD in the United States in a 10-year-old patient with idiopathic dilated cardiomyopathy who was then successfully bridged to transplantation.
A previously healthy 10-year-old girl (body surface area, 1.2 m2) was transferred to our institution for further management of newly diagnosed nonischemic dilated cardiomyopathy. Cardiac catheterization revealed a cardiac index of 1.5 L/min/m2, mixed venous oxygen saturation of 38%, left ventricular end-diastolic pressure of 30 mm Hg, left ventricular ejection fraction of 7%, pulmonary artery pressure of 45/33 mm Hg, pulmonary vascular resistance of 6.7 wood units · m2, and moderate mitral and tricuspid valve regurgitation. Right ventricular function was relatively preserved, although the right ventricular end-diastolic pressure was 15 mm Hg. An endomyocardial biopsy demonstrated nonspecific interstitial fibrosis consistent with idiopathic dilated cardiomyopathy, and the patient was listed for heart transplantation. She was given intravenous infusions of dopamine, milrinone, and furosemide, with some clinical improvement. Ultimately, however, she had intermittent runs of nonsustained ventricular tachycardia, renal insufficiency, and abdominal pain develop. As her clinical status deteriorated, implantation of an LVAD was proposed. Permission to perform the implantation using the MDBVAD was granted by the University of Michigan's Institutional Review Board.
Implantation was performed on January 30, 2003 using previously described techniques [3]. Normothermic cardiopulmonary bypass was instituted through a median sternotomy. The inflow cannula was inserted in the left ventricular apex, the pump was placed in a preperitoneal pocket, and the outflow graft was anastomosed end-to-side to the right anterolateral aspect of the proximal ascending aorta (Fig 1). The drive line was tunneled to exit above the patient's right iliac crest. As the implant was completed, the heart was slowly filled, and the device was started at an initial speed of 7,500 rpm. As the patient was gradually weaned from cardiopulmonary bypass, the pump speed was increased to 9,000 rpm to maintain a cardiac index between 1.8 and 2.0 L/min/m2. The total cardiopulmonary bypass time was 142 minutes and aortic cross-clamping was not necessary. Bleeding was minimal. The patient was transferred to the intensive care unit with stable hemodynamics on standard inotropic pharmacological support. The patient was extubated on postoperative day 2. Her subsequent recovery was uneventful. Preoperative and postoperative chest roentgenograms are shown in Figure 2. Right ventricular function was borderline, and an infusion of dopamine at 3 mcg/kg/min infusion was maintained. The pump speed was subsequently increased to 9,500 rpm, which provided a device flow between 2.0 and 3.0 L/min/m2. Pre-load was modulated by oral intake. The device was readily managed by both the nursing staff and the patient's family. Heparin was started on postoperative day 3, and the patient's anticogulation regimen was subsequently transitioned to a combination of aspirin, warfarin (to maintain an international normalized ratio between 2.5 and 3.5), and clopidogrel. Hemolysis was detected by standard laboratory indices and there was a gradual decline in the hematocrit (Table 1), but this was not clinically significant, and transfusion was not required. Due to persistent right ventricular dysfunction, the low-dose dopamine infusion could not be weaned. Echocardiography showed failure of the aortic valve to open and no improvement in ventricular function during the period of support. The average pulse pressure measured during LVAD support was 10 mm Hg. The patient's overall health improved dramatically after LVAD implantation. Organ function recovered (Table 1), and patient mobility was maintained.
View larger version (86K):
[in this window]
[in a new window]
|
Fig 1. Intraoperative photograph of implanted device. The outflow graft and flow probe are seen, while the pump and inflow cannula are hidden from view.
|
|
View larger version (97K):
[in this window]
[in a new window]
|
Fig 2. Preoperative chest roentgenogram (A) and chest roentgenogram after MicroMed DeBakey left ventricular assist device implantation (B).
|
|
The patient remained in the hospital receiving a dopamine infusion until a suitable donor organ could be identified. She underwent orthotopic heart transplantation 84 days after LVAD implantation. Due to extensive mediastinal adhesions, cardiopulmonary bypass was electively initiated by the femoral approach to facilitate the dissection. The LVAD was explanted and orthotopic heart transplantation was performed using a bi-caval technique. Total cardiopulmonary bypass time was 335 minutes (prolonged primarily by a delay at the donor hospital), whereas the total donor ischemia time was 75 minutes. The patient had a severe coagulopathy develop that required transfusion of multiple units of blood products. Hemostasis was ultimately achieved, and she was transferred to the intensive care unit with stable hemodynamics. Her postoperative course was uncomplicated. She was extubated after 24 hours and was transferred to general care on the postoperative day 3. The patient was discharged home on postoperative day 11 on standard immunosuppressive therapy.
|
Comment
|
|---|
The use of ventricular assist devices in adult patients with end-stage heart failure has resulted in a clinically meaningful survival benefit and an improved quality of life [1, 2]. However, the pediatric experience with this modality remains relatively limited. The most common form of mechanical circulatory support in the pediatric population is ECMO. Many centers have reported success using ECMO in pediatric patients with primary and postcardiotomy failure as a form of rescue therapy or as a bridge to transplantation [5–8]. Although ECMO has a number of advantages including versatility, ease of implementation, and familiarity, this modality has a number of disadvantages, including immobilization, requirement for intensive care monitoring, and risks of bleeding, thrombosis, infection, and multiorgan failure. These attendant disadvantages, which increase over time, hamper the use of ECMO for long-term support.
Experience with ventricular assist devices in children is increasing, as smaller devices are becoming available. Hetzer and colleagues [9] reported results of the Berlin Heart ventricular assist device (a pneumatic paracorporeal assist device) in a critically ill group of pediatric patients ranging in age from 6 days to 16 years. The authors reported an overall survival of 40%. The most frequently observed complication was postoperative bleeding.
Recently, the MDBVAD has been demonstrated to be a valid option for bridge-to-transplantation in the adult population [3, 4]. This device is an implantable electromagnetically-actuated axial flow pump. The initial multicenter experience has demonstrated a post-implantation 30-day survival of 81%; also, nearly one-third of the patients undergoing implantation have undergone a successful transplant after a median time of support of 74.5 days [3]. Major advantages of this device include ease of implantation, reduced size, ready patient mobilization post-implant, and the possibility for discharge home while waiting for transplant. No infections were reported after implant. The incidence of post-implant bleeding was the major complication.
The ventricular assist devices currently available in the United States for small pediatric patients (BSA < 1.4) have been essentially limited to the Thoratec, Abiomed, and centrifugal pump systems. We believe that the MDBVAD offered distinct advantages with respect to implantability, maintenance of patient mobility, and possibly a lower thromboembolic risk.
This report describes the first pediatric implantation of the MDBVAD in the United States. This patient also represented the youngest implant to date worldwide. Our experience has confirmed the reported encouraging results. The patient's physiologic and psychological status improved dramatically after LVAD implantation. LVAD function did not precipitate right ventricular dysfunction, although overall cardiac output was clearly right ventricular dependent. Postoperative mortality after MDBVAD has been strongly related to preoperative morbidity [3, 4]. Early timing of LVAD implant prior to development of multisystem organ failure is likely to be critical for success.
Despite its promise, the MDBVAD has a number of limitations. First, as with all LVADs, its application is limited to patients with normal pulmonary function. Second, although it is much smaller than existing pulsatile LVAD designs, it is still much too large for use in neonates and small children. In general, the MDVAD is limited to patients with a body surface area of 1.2 m2 or greater, although a modified version of the pump (DeBakey VAD Child System) has subsequently been introduced for use in patients 5 to 16 years of age (body surface area, > 0.7 m2). In this patient, significant hemolysis became evident toward the end of support. This was believed to be secondary to pump thrombus. Finally, like many other LVADs, it requires full anticoagulation. Future technological improvement will likely provide surgeons with miniaturized pumps that can be accommodated by smaller children and infants.
In conclusion, we report the feasibility of MDBVAD as a device for ventricular support in children. Early implantation is recommended to preserve organ function for a successful bridge to transplantation.
|
References
|
|---|
- Frazier OH, Rose EA, Oz MC, et al. Multicenter clinical evaluation of the HeartMate vented electric left ventricular assist system in patients awaiting heart transplantation J Thorac Cardiovasc Surg 2001;122:1186-1195.[Abstract/Free Full Text]
- Rose EA, Gelijns AC, Moskowitz AJ, et al. Long-term mechanical left ventricular assistance for end-stage heart failure N Engl J Med 2001;345:1435-1443.[Abstract/Free Full Text]
- Noon GP, Morley DL, Irwin S, Abdelsayed SV, Benkowski RJ, Lynch BE. Clinical experience with the MicroMed DeBakey ventricular assist device Ann Thorac Surg 2001;71:S133-S138discussion S144-6.[Medline]
- Grinda JM, Latremouille CH, Chevalier P, et al. Bridge to transplantation with the DeBakey VAD axial pumpa single center report. Eur J Cardiothorac Surg 2002;22:965-970.[Abstract/Free Full Text]
- Gajarski RJ, Mosca RS, Ohye RG, et al. Use of extracorporeal life support as a bridge to pediatric cardiac transplantation J Heart Lung Transplant 2003;22:28-34.[Medline]
- Duncan BW, Hraska V, Jonas RA, et al. Mechanical circulatory support in children with cardiac disease J Thorac Cardiovasc Surg 1999;117:529-542.[Abstract/Free Full Text]
- Kirshbom PM, Bridges ND, Myung RJ, Gaynor JW, Clark BJ, Spray TL. Use of extracorporeal membrane oxygenation in pediatric thoracic organ transplantation J Thorac Cardiovasc Surg 2002;123:130-136.[Abstract/Free Full Text]
- Kulik TJ, Moler FW, Palmisano JM, et al. Outcome-associated factors in pediatric patients treated with extracorporeal membrane oxygenator after cardiac surgery Circulation 1996;94:II63-II68.[Medline]
- Hetzer R, Loebe M, Potapov EV, et al. Circulatory support with pneumatic paracorporeal ventricular assist device in infants and children Ann Thorac Surg 1998;66:1498-1506.[Abstract/Free Full Text]
Top
Abstract
Introduction
