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Ann Thorac Surg 2005;80:1920-1922
© 2005 The Society of Thoracic Surgeons
Department of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota, USA
Accepted for publication June 11, 2004.
* Address correspondence to Dr Daly, Department of Cardiovascular Surgery, Mayo Clinic Rochester, 200 First St, SW, Rochester, MN55902 (Email: daly.richard{at}mayo.edu).
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Introduction |
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We report the smallest patient known to date to undergo biventricular support with the Thoratec VAD (Thoratec Corp) as a bridge to subsequent successful transplantation. We detail the clinical course, operative modifications, pump settings, and complications arising in this small patient.
A 124 cm, 17.1 kg (dry weight, body surface area, 0.77 m2), 7-year-old girl was diagnosed with an asymptomatic heart murmur during examination for a viral illness. Four months later, echocardiography demonstrated mild left ventricular dilatation. Subsequently she had fatigue, abdominal pain, shortness of breath, and mild cyanosis develop. Nine months after her initial viral illness, repeat echocardiography demonstrated a dilated left ventricle with an ejection fraction of 13%, left ventricular thrombus, grade III-IV mitral regurgitation, moderate pulmonary regurgitation, estimated pulmonary artery pressure of 40/20 mm Hg, severe right ventricular dilatation, right ventricular ejection fraction of 20%, and severe tricuspid regurgitation. The patient was hospitalized and pharmacologic treatment was initiated. However she continued to deteriorate and became dependent on multiple infusions including dopamine, dobutamine, epinephrine, nitroprusside, milrinone, and amiodarone.
Three days after hospital admission, the patient's extremities became cool and mottled; she became anuric and required mechanical ventilation. Right atrial pressure was 27 mm Hg. The evolving cardiogenic shock was accompanied by an episode of ventricular tachycardia. The decision was made to proceed with mechanical circulatory support as a bridge to cardiac transplantation.
At operation the heart was markedly dilated and tense. Intraoperative transesophageal echocardiography demonstrated a left ventricle ejection fraction of 10%, severe mitral regurgitation, severely impaired right ventricular function, and severe tricuspid regurgitation. With the significant cardiomegaly, it was believed likely there would be enough room for the Thoratec cannulas and conduits (Thoratec Corp) once the heart was decompressed.
Cardiopulmonary bypass was established with aortic and right atrial cannulation. The left-sided Thoratec VAD (Thoratec Corp) was implanted with an inflow apical left ventricular cannula and an outflow cannula to the ascending aorta. The cannulas for the right-sided VAD included a 51-French right-angled venous cannula in the right atrium and an outflow cannula to the pulmonary trunk. The outflow cannulas were both pre-clotted 14-mm Dacron grafts. All were standard Thoratec cannulas (Thoratec Corp). Two 7 cm lengths of 10-mm Hemashield Dacron grafts were interposed between the patient's aorta and pulmonary arteries (end-to-side) and the VAD outflow grafts (end-to-end) to taper between the discrepant diameters. The cannulas were passed through tunnels to the subcostal region in the epigastric area and were connected to the extracorporeal Thoratec pump heads (Thoratec Corp) in an air-free manner. The aortic graft lay to the right, behind the right atrial cannula, and passed posterior to the pulmonary arterial cannula before entering its tunnel. The pumps were initially placed in the volume (fill-to-empty) mode, and flows of 4 to 5 L/min were obtained. With satisfactory cardiac decompression by the VADs, it was possible to close the sternum despite the bulk of the VAD cannulas. Hemodynamic status and pump flows remained stable during chest closure.
The patient was extubated 5 days later. She was anticoagulated with heparin to maintain a partial thromboplastin time of 60 to 70 seconds and was stabilized on low doses of dopamine, nitroprusside, and amiodarone infusions. After several hours, the Thoratec device (Thoratec Corp) was changed from the volume mode to the fixed rate mode at a high set rate to reduce the stroke volume of the device. At the set rates selected (90 to 120 beats/min) the VAD chambers filled submaximally; however complete emptying of the pneumatic chamber was documented by physical inspection of the device (a "flash" at end systole noted with a light held behind the chamber). Adequate flow was assessed by physical examination of the patient, ensuring warm extremities and urine output greater than 1 mL/kg/h.
During biventricular VAD support, the patient had several complications. An episode of pulmonary aspiration required reintubation. Gastrointestinal bleeding was managed by withholding anticoagulation for 12 hours, and interventional endoscopic techniques were utilized to diagnose and control erosive gastric lesions.
Eighteen days after BiVAD Thoratec (Thoratec Corp) placement, the patient underwent removal of the device and orthotopic heart transplantation. There was no evidence of thrombus in the devices, grafts, or cannulas. The patient's chest was left open to optimize donor heart function and hemodynamics. Almost immediately after her return to the intensive care unit, she had evidence of right ventricular failure develop. She was returned to the operating room and an Abiomed BVS 5000 (Abiomed Inc, Danvers, MA) right ventricular assist device was inserted. After placement of the right ventricular assist device, she had massive hemoptysis leading to hypoxia and ventricular fibrillation develop. Support was successfully changed to extracorporeal membrane oxygenation.
Postoperative anuria was treated by continuous veno-veno hemodialysis. Coagulopathy led to multiple episodes of spontaneous mediastinal and left thoracic hemorrhage, which were managed by repeat mediastinal explorations and a left thoracotomy.
Pulmonary hypertension was treated with intravenous vasodilators and inhaled nitric oxide. Extracorporeal membrane oxygenation was successfully discontinued 9 days posttransplantation. Eighteen days after transplantation, primary chest closure was performed. Infusions were gradually weaned during the following week, and the patient was free from inotropic support by 22 days postoperatively. Echocardiography demonstrated the left ventricle ejection fraction was 50% at 28 days posttransplantation. A permanent pacemaker was placed 37 days postoperatively for sinus bradycardia. The patient underwent successful rehabilitation. She continues to do well 3 years after transplantation.
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These modifications attempt to address the published concern that high flows and pressures may be responsible for adverse neurologic sequelae in small patients [3]. It is possible that this patient had relatively high pulmonary pressures and flows on the device, in spite of the described modified settings, which may have contributed to pulmonary hypertension and massive hemoptysis posttransplantation.
One recent series details the use of the Thoratec device (Thoratec Corp) for either univentricular or biventricular support in small patients (17 to 20 kg) with myocarditis and cardiomyopathies reporting a survival similar to that seen in adults (72%) [3]. Our report builds on published experience with the Thoratec VAD (Thoratec Corp) by demonstrating utilization of the device for biventricular support as a successful bridge to transplantation in the smallest known surviving patient to date. Moreover, we have described details necessary for the modification of this adult-type pump to effectively support the small pediatric patient.
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