The Berlin Heart EXCOR® in an 11-Year-Old Boy

Abstract

When a donor heart is not available during the end stage of heart failure, the implantation of a ventricular assist device is the only therapeutic alternative. Many such devices are designed to provide circulatory support to adults, but very few are available for children and infants, especially in the United States. In children, implantation of ventricular assist devices that are designed for adults carries a high risk of complications, because the low stroke volumes that must be used can result in inadequate pump washout and excessive thromboembolic risk.

Herein, we report the case of an 11-year-old boy with congenital heart defects who experienced acute myocardial infarction. Prolonged support with the Berlin Heart excor® Pediatric ventricular assist device served as a bridge to recovery. The period after device implantation was challenging, because of the need for prolonged inotropic support, continuous mechanical ventilation, the number of reoperations, and the occurrence of sepsis. Nevertheless, after 29 days, the patient's heart recovered, and the device was explanted. He was discharged from the hospital, in good condition, 30 days after removal of the excor® device.

When a donor heart is unavailable during end-stage heart failure, the only therapeutic alternative is the implantation of a ventricular assist device (VAD).¹ Many VADs, both pulsatile and laminar, are designed for use in adults. Examples include the HeartMate® (Thoratec Corporation; Pleasanton, Calif),² the Thoratec® (Thoratec),³ the abiomed® biventricular support system (BVS 5000®, abiomed, Inc.; Danvers, Mass),⁴ the MicroMed DeBakey VAD® (MicroMed Technology, Inc.; Houston, Tex),⁵ the Jarvik 2000 FlowMaker® (Jarvik Heart, Inc.; New York, NY),⁶ and the Berlin Heart excor® and incor® systems (Berlin Heart GmbH; Berlin, Germany).^1,7,8 However, far fewer implantable VADs are available for infants and children, especially in the United States.⁹ Some VADs that were designed primarily for adults have been successfully used^3,4 in children older than 11 years of age and with body surface areas greater than 1.2 m². However, in small children, infants, and newborns, the use of VADs designed for adults is unsafe, because of the low stroke volumes that must be used. The result is inadequate pump washout and an excessive thromboembolic risk.^4,9

The Berlin Heart excor® Pediatric VAD is a pulsatile assist device that comprises a compressor and pumps (artificial ventricles); it is connected to the heart with cannulas.⁷ The device's pumps are designed to provide different stroke volumes: 10 mL (suitable for newborns), 25 and 30 mL (suitable for infants and children with body surface areas <1.2 m²), and 50 and 60 mL (suitable for adults and larger children). These stroke volumes in pumps designed for children of various sizes will enable proper washout of the pumps.

Our search of the medical literature revealed few reports regarding the use of the Berlin Heart excor Pediatric VAD in pediatric patients.^7,10–12 Herein, we report the case of an 11-year-old boy who experienced acute myocardial infarction and received prolonged support from the Berlin Heart excor Pediatric VAD.

Case Report

In March 2005, an 11-year-old boy (height, 143 cm; weight, 31 kg; body surface area, 1.11 m²) was diagnosed as having an ostium secundum atrial septal defect (ASD), a cleft in the anterior mitral leaflet, and grade 2 mitral regurgitation. In May 2005, the boy was admitted to our hospital for scheduled closure of the ASD and repair of the mitral valve. Preoperative transthoracic echocardiography (TTE) showed a left ventricular end-diastolic volume (LVEDV) of 35.5 mL, a left ventricular end-systolic volume (LVESV) of 18.9 mL, a stroke volume (SV) of 16.4 mL, left ventricular ejection fraction (LVEF) of 0.46, right ventricular diameter of 22.7 mm, and left ventricular diameter (LVD) of 38.7 mm.

Two days later, we closed the ASD with a pericardial patch, performed mitral valve annuloplasty with a 28-mm Edwards Lifesciences ring (Edwards Lifesciences LLC; Irvine, Calif), and sutured the cleft in the anterior mitral leaflet. The patient was weaned from extracorporeal circulation by use of dopamine (2 mL/hr) and, because of complete atrioventricular block, a ventricular pacemaker was placed.

The patient was extubated 5 hours after the operation. Postoperative TTE showed complete ASD closure without a residual left-to-right shunt. Mitral regurgitation was negligible. Other data included (Table I) LVEDV, 50.6 mL; LVESV, 29.3 mL; SV, 21.3 mL; LVEF, 0.42; and LVD, 43 mm.

TABLE I. Selected Echocardiographic Measurements throughout the Patient's Treatment

On the 2nd postoperative day (May 19), the patient began to experience acute precordial pain. Acute heart failure and pulmonary edema rapidly developed. The patient was reintubated. Intravenous dobutamine (8 mL/hr), epinephrine (4 mL/hr), milrinone (1 mL/hr), and furosemide (3 mL/hr) were administered without effect. Continuous veno-venous hemofiltration was also started (filtration volume, 100 mL/hr). Global hypokinesia and akinesia of the left ventricle (LVEDV, 38.3 mL; LVESV, 35 mL; SV, 3.3 mL; and LVEF, 0.09) were identified on TTE. An electrocardiogram showed signs of acute myocardial infarction. Test results for the presence of cardiac troponin T were positive. Because of ventricular fibrillation, defibrillation was performed several times, but without effect. The patient's chest was opened in the intensive care unit, and direct heart compressions were started. He was then taken for emergency surgery. Extracorporeal circulation was started. The left anterior descending coronary artery was opened and inspected by means of a small Fogarty arterial embolectomy catheter. There was no flow from the proximal segment of the artery. Although we were unable to remove any embolic material, we observed excellent antegrade flow after the inspection. The artery was reconstructed by use of a venous patch. After several unsuccessful attempts to wean the patient from extracorporeal circulation, we implanted a Berlin Heart excor Pediatric VAD. The device was implanted as a left VAD, with the inflow cannula in the left atrium and the outflow cannula in the ascending aorta. Because the patient's body surface area was 1.11 m², a 30-mL pump was used.

The patient remained in critical condition. Immediately after the VAD implantation, global hypokinesia and akinesia of the left ventricle persisted. The ASD was without residual shunt, and mitral regurgitation was negligible. However, we detected a protrusion of the annuloplasty ring, and aortic regurgitation up to grade 2. Other data were as follows: LVEDV, 48 mL; LVESV, 43.2 mL; SV, 4.8 mL; and LVEF, 0.10. His chest was left open for 3 days before we closed the sternum.

The patient was supported on mechanical ventilation for 14 days. Prolonged intravenous inotropic support was required: epinephrine (1 mL/hr over 2 days), dobutamine (6 mL/hr over 3 days), and dopamine (3 mL/hr over 21 days). On the 10th day after implantation, pericardial tamponade developed, and 350 mL of effusion was evacuated during a reoperation. Because of hemodynamic instability after the operation, the patient's chest was left open; it was closed 2 days later. After extubation, the patient experienced severe nosebleed, and a number of posterior tampons were required.

Because of leukocytosis and a number of febrile crises that began 9 days after VAD implantation, levofloxacin (250 mg twice daily for 4 days), teicoplanin (300 mg twice daily for 14 days), and imipenem (500 mg 4 times daily for 14 days) were added to the therapy. Immunovenin-Intact® 5% IgG (human normal immunoglobulin for intravenous administration, Bul Bio–NCIPD Ltd.; Sofia, Bulgaria) (one 10-mL phial daily over 3 days) and Pentaglobin® (Biotest AG; Dreieich, Germany) (one 100-mL phial daily over 7 days) were also infused. To prevent mycosis, itraconazole (5 mL twice daily for 10 days) and fluconazole (100 mg/day for 14 days) were given. The infection resolved, and the excor pump was not infected. Several successive blood cultures proved sterile.

Ventricular function was evaluated daily by means of TTE. During the postoperative period, we observed a gradual improvement in left ventricular function (Table I).

On the 29th day after implantation (16 June), the excor VAD was removed, and the ascending aorta was reconstructed with a patch, constructed from a Unigraft prosthesis (B. Braun Melsungen AG; Melsungen, Germany). Weaning of the patient from extracorporeal circulation was effected with dopamine (4 mL/hr) and dobutamine (2 mL/hr). The patient was extubated 12 hours after explantation, but prolonged inotropic support with dobutamine (3 mL/hr for 10 days) and dopamine (2 mL/hr for 20 days) was required to maintain hemodynamic stability.

Just before the explantation, TTE showed an LVEDV of 30.0 mL; LVESV, 18.7 mL; SV, 11.3 mL; and LVEF, 0.38. Immediately after explantation, TTE showed an LVEDV of 35.8 mL; LVESV, 18.3 mL; SV, 17.5 mL; and LVEF, 0.49. The next day, TTE showed LVEDV of 39.6 mL, LVESV of 23.6 mL, SV of 16 mL, and LVEF of 0.40.

On the 3rd day after explantation, TTE showed that a substantial amount of fluid had collected in the pericardial cavity, and the patient underwent reoperation. However, the amount of fluid was substantially overestimated, and less than 100 mL of pericardial effusion was drained. Thereafter, the patient's chest was left open with only the skin sutured. Continuous veno-venous hemofiltration was started at a filtration rate of 150 mL/hr and was continued for 2 days. Sternal closure was performed on 23 June, 5 days after this reoperation.

During the first few days after explantation, the patient's condition remained stable. However, leukocytosis recurred, and the patient experienced a number of septic febrile crises (body temperatures of up to 40 °C) that began the day after the pericardial drainage. Enterobacter cloacae grew in one of several blood cultures. Amikacin (500 mg daily for 3 days), teicoplanin (300 mg twice daily for 13 days), and imipenem (4 daily doses of 500 mg for 19 days) were added to the therapy. Several Pentaglobin® infusions (1 phial daily over 5 days) and one of Immunovenin Intact® 5% IgG were administered. Oral itraconazole (5 mL twice daily for 10 days) and fluconazole (100 mg/day for 14 days) were administered to prevent mycosis.

On 5 July, as soon as the E. cloacae infection was considered cured, a permanent pacemaker (Affinity™ DR 5330 R, St. Jude Medical; St. Paul, Minn) was implanted, because of irreversible complete atrioventricular block. The patient continued to receive imipenem for 7 more days.

On the 30th day after explantation of the VAD, the patient was discharged from the hospital in good condition—afebrile, hemodynamically stable, and able to undertake daily activities. Electrocardiography showed a heart rate of 125 beats/min and pacemaker spikes; laboratory test results were within normal limits; and TTE showed septal dyskinesis, very good activity of the left ventricular posterior wall, continuing protrusion of the annuloplasty ring, and mitral regurgitation up to grade 1. Aortic regurgitation was no greater than grade 2. Other data included an LVEDV of 46 mL; LVESV, 20 mL; SV, 22 mL; LVEF, 0.55; and right ventricular end-diastolic pressure, 25 mmHg. Two years after the surgery, the patient was in New York Heart Association functional class I and was doing well. His last TTE examination showed an LVEF of 0.55, grade-1 aortic regurgitation, and grade-1 mitral regurgitation.

Discussion

In children, acute heart failure is not rare; its most common causes are myocarditis, congenital heart diseases, and supraventricular tachycardias.⁷ On the other hand, acute myocardial infarction is a rare cause of acute heart failure in children—for example, in patients with Kawasaki disease.^13,14 Although we were unable to identify the cause of the myocardial infarction in our young patient, we speculate that it was caused by particle or thrombotic embolism.

The pumps of the Berlin Heart excor Pediatric VAD are designed to have different stroke volumes (10, 25, 30, 50, or 60 mL).¹⁵ From all of the pumps available, we chose the 30-mL pump, because the patient's body surface area was 1.11 m². According to the available medical literature,⁷ pumps of this size are suitable for patients who have a body surface area less than 1.2 m². BerlinHeart GmbH, the manufacturer of the excor, also recommends use of the 30-mL pump in patients who weigh 20 to 30 kg.¹⁵

Stiller and colleagues⁷ reported that the excor Pediatric VAD can enable the recovery of myocardial function in children after fulminant myocarditis. Our 11-year-old patient recovered from acute myocardial infarction, severe myocardial injury, and low LVEF, by means of prolonged excor support. Our patient's LVEF before excor implantation was 0.09, but it had risen to 0.55 upon his discharge from the hospital.

Although our experience was restricted to a single case, we suggest that the Berlin Heart excor Pediatric VAD has pumps designed with different stroke volumes that can be safely used in small children, infants, and newborns. Use of the excor Pediatric VAD incurs a reduced risk of thromboembolic events when compared with VADs designed for adults,^7–12 and the device can serve as a bridge to recovery in critically ill pediatric patients.

Statement of Compliance

Because the Berlin Heart excor Pediatric VAD is in the process of undergoing FDA approval, this study was performed in compliance with FDA guidelines. Informed written consent was obtained from the parents of the patient after the nature of all procedures was explained.