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Ann Thorac Surg 1998;66:1498-1506
© 1998 The Society of Thoracic Surgeons
a Department of Cardiac, Thoracic and Vascular Surgery, Deutsches Herzzentrum Berlin, Berlin, Germany
b Department of Pediatric Cardiology and Congenital Heart Disease, Deutsches Herzzentrum Berlin, Berlin, Germany
Address reprint requests to Dr Hetzer, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
e-mail: (hetzer{at}dhzb.de)
Presented at the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Methods. In 28 children—ages between 6 days and 16 years—the Berlin Heart VAD has been applied for periods of between 12 hours and 98 days (mean, 16.9 days) aiming at keeping the patient alive and allowing for recovery from shock sequelae until later transplantation or myocardial recovery. There were three groups. Group I: with primary intention of "bridge-to-transplantation" in various forms of cardiomyopathy (n = 13) or chronic stages of congenital heart disease (n = 5). Group II: "Rescue" in intractable heart failure early after corrective surgery for congenital heart disease (n = 4) or in early graft failure after a heart transplantation (n = 1). Group III: "Acute myocarditis" (n = 5) aiming at either myocardial recovery or transplantation. Twelve were brought to the operating room under cardiac massage and 25 had been on the respirator for more than 24 hours.
Results. Twelve patients died on the system from sequelae of profound shock—multiorgan failure, sepsis, loss of peripheral circulatory resistance—or from hemorrhagic complications (n = 4) or brain death (n = 1). Thirteen patients (groups I and III) were transplanted after support periods of between 3 and 98 days with 7 long-term survivors living now up to 7.5 years (mean, 4.4 years). Three patients (groups II and III) were weaned from the system with two long-term survivors (both in group III). There were no patients in group II who survived and the "rescue" indication has been discarded for VAD since 1992. Such patients are since treated by extracorporeal membrane oxygenation (ECMO) in our institution. Out of the 8 patients placed on VAD during 1996 and 1997, 7 were successfully supported until transplantation or weaning. Thirteen patients were extubated and mobilized on the system. Whereas with the earlier systems thrombi in the blood pumps were seen in 15 instances and 2 patients suffered from thromboembolic complications, no thrombotic events occurred with the heparin-coated systems.
Conclusions. After accumulating clinical experience and several technical improvements since 1990 the use of the pediatric Berlin Heart VAD has matured into a reliable and safe system to keep patients with otherwise intractable heart failure alive until complete myocardial recovery is reached or transplantation becomes feasible. Whereas heart failure early after cardiac operation is now primarily treated by ECMO, acute myocarditis appears to be a promising precondition for complete cardiac recovery during VAD support.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Most companies producing such assist devices have not recommended their application in children below adult body size and no pediatric-size pumps had been produced until 1992 when "Berlin Heart" offered worldwide the first commercially available system with miniaturized paracorporeal pumps and cannulae. This development followed our demand for a spectrum of pumps for every body size and age after our initial experience with school children, where we applied adult-size Berlin Heart pumps which had become available in 1988 [2].
The first reported case of a child—8 years old—supported for 8 days in intractable circulatory failure succeeded with a successful transplantation and an uneventful course since then was handled with an adult-size 50 mL Berlin Heart left ventricular assist device (LVAD) at our institution [3].
Most pediatric cardiac surgery departments have continued to use centrifugal pumps or ECMO (extracorporeal membrane oxygenation) as a support system for days and sometimes weeks [4]. During recent years we have preferred ECMO in patients with intracardiac shunts, very small infants and postcardiotomy. But in children who, in respect to their heart disease, would have to await heart transplantation with unknown waiting periods we used the paracorporeal pneumatically driven, pulsatile Berlin Heart system mostly in a biventricular support configuration.
The present report is based on the experience with the Berlin Heart system in children under the age of 16 years between 1990 and December 1997.
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Patients and methods |
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There were three main groups of patients according to underlying disease and anticipated treatment concepts (Table 1).
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Thirteen children suffered from cardiomyopathy of various origins (idiopathic, toxic, endocardial fibrosis, chronic recurrent myocarditis). There was 1 child with severe chronic left heart failure in aortic stenosis untreatable by conventional surgery, 1 with myocardial infarct in pulmonary atresia, intact septum, and coronary sinusoids, and 2 children with transposition of the great arteries at long-term after atrial corrective surgery (one Mustard, one Senning).
Group II ("rescue")
This group includes 5 children with heart failure early after corrective operations for congenital heart defects. The implantation of the assist system was performed either immediately (patient 11) or between 1 and 8 days after the initial open-heart operation, invariably after at least one episode of cardiopulmonary resuscitation (CPR). Ventricular assist devices aimed at keeping the patient alive, leaving the future procedure open to consideration according to the clinical course, ie, either recovery and weaning or transplantation. The underlying defect and the operation were: Fontan operation for univentricular heart, closure of ventricular septal defect, Norwood operation for hypoplastic left heart syndrome, systemic-to-pulmonary shunt in pulmonary atresia, intact septum and sinusoids, and early graft failure after heart transplantation.
The ages of these children were 2 weeks, 6 months, 10 months, and 4 and 5 years.
Group III (acute myocarditis)
In this group, 5 patients are listed who presented with acute, mostly viral myocarditis who could not be maintained by conservative means and in whom either recovery or transplantation was anticipated. Four children had CPR before assist implantation and were brought to the operating room under continuous chest massage until extracorporeal circulation (ECC) was installed. The duration of heart failure in these children had been between 2 and 22 days.
The assist device
The Berlin Heart VAD system produced by Mediport Kardiotechnik, Berlin, Germany consists of a paracorporeal air-driven blood pump, cannulae for connection of the pumps to the heart chambers and the great vessels and electropneumatic driving systems (Figs 1–3).
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For the small blood pumps (12 mL and 15 mL) an optional modification was introduced by interposing an elastic polyurethane reservoir between the atrial cannula and the inflow chamber port, thus remarkably improving chamber filling (Fig 2).
A set of atrial and arterial silicone cannulae with inner diameter of 12.7, 9.5, 6.4, and 3.2 mm is available which allows for individual system assembly according to patient anatomy.
The atrial cannulae are supplied with a basket tip of three different angles (45, 60, and 85 degrees) and a sewing ring (Fig 1). The arterial return cannulae have a Dacron-velour (C.R. Bard, Haverhill, PA) covered sewing rim at their end which allows for end-to-side anastomosis to either the aorta or the pulmonary artery. The middle portion of these cannulae is surrounded by a Dacron-velour surface which promotes tissue ingrowth, thus providing a shield against infection migration along the skin tunnel.
In the few cases of left ventricular drainage, in one instance a right-angled cannula with side holes near the tip was inserted via the left upper pulmonary vein, the left atrium and across the mitral valve, in the other case direct left ventricular apical drainage was provided with a basket-tipped straight venous ECC cannula.
A variety of cannulae for infants and small children have been tried. Whereas the atrial drainage cannulae of miniaturized size have proven satisfactory, the arterial return cannulae remain a difficult field. This is why in most cases indwelling regular ECC arterial return cannulae were applied, which, however, pose a significant resistance to the heart chambers, when weaning from the pump was attempted. Only recently a small size arterial return cannula has been developed which has a flat metal tip and sewing ring at its 85-degree angled end resembling a press-button (Fig 3). The metal tip is inserted into the arterial lumen and allows for secure fixation at the arterial wall by means of the sewing ring. This configuration ensures that there will not be any undue resistance to natural heart output.
Since 1994 all blood-contacting polyurethane surfaces have been heparin-coated (Carmeda, Stockholm, Sweden), which has been applied in the patients 18 to 28.
Two different driving systems have been in use in the pediatric patients (Fig 4). Because the resistance of the small-bore cannulae is high during pump operation, positive systolic pressures of up to 350 mm Hg and negative diastolic suction pressures of 100 mm Hg at pumping rates of up to 140 beats/min are reached. Therefore, power requirements are considerably higher than in adult pump operation.
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The driving unit that has been alternatively used at our institution, the Heimes HD-7, has a lesser weight and provides a somewhat greater mobility, it is, however, limited by smaller driving power. Both drive units have completely redundant back-up systems.
Implantation and management of the assist devices and treatment of patients
In most cases (except for 3 with LVAD only) the patients were placed on conventional ECC which greatly facilitates the assist implant. The cannulae are secured by either pledgeted mattress sutures or, in the smaller children, by purse-string sutures and tourniquets. When the cannulae have been brought across the skin via tight-fitting skin incisions, the pumps were connected, deaired and assist circulation was begun and ECC stopped.
All children were kept on intravenous heparin, aiming at activated clotting time levels of between 140 and 160 seconds. Coumadin and antiplatlet agents were not used in pediatric patients. The anticoagulation regiment remained unchanged when heparin-coated VADs became available.
For infection prophylaxis antistaphylococcal antibiotics were administered throughout the support period.
In children in whom transplantation was planned, a state called "transplantability" was defined when organ recovery was complete, the patient was without severe neurological deficits, preferably awake and extubated and without infection (Figs 5–7).
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Statistical analysis
Categorical variables were evaluated using 
2 analysis with p < 0.05 considered statistically significant. Nonparametric ordinal variables were evaluated using the Mann-Whitney U test. All statistical analysis were performed using SPSS for Windows, Release 6.0 (SPSS, Inc. 1989–1993, Chicago, IL).
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Sixteen were taken off the assist system, either after complete cardiac recovery or at time of transplantation. Twelve patients died from either loss of peripheral circulatory resistance unresponsive to 
-receptor stimulants, due to multi-organ damage or due to sepsis, or from hemorrhagic complications on the assist system.
In group I, 12 of 18 patients reached the goal of recovery from shock sequelae and were judged "transplantable." Two patients died after transplantation from right heart failure due to high pulmonary vascular resistance and 2 more patients died from graft failure, 1 of whom was placed on ECMO after heart transplantation and succumbed to circulatory failure with sepsis. One patient acquired fungal disease and died from sepsis 3 months post transplant. Seven patients were discharged after heart transplantation from hospital, 1 had an operation for coarctation 18 months after the transplant. The transplanted patients were treated with our triple immunosuppressive regimen [5] and rejection was monitored with the IMEG system developed in our department [6, 7]. Presently all 7 long-term survivors are alive, between 10 months and 7
years after transplantation with good graft function and uneventful further development.
All 5 patients in group II died after between 12 hours and 8 days of mechanical support, all from causes related to the severity of preceding circulatory failure, ie, multiorgan failure with loss of circulatory resistance, brain death, pulmonary failure, and diffuse hemorrhage. The patient with early graft failure after transplantation (patient 13) was weaned from VAD, however, the patient suffered rapidly recurring graft failure.
In group III, 2 patients who were brought to the operating room under continuous chest massage died after 2 and 16 days from peripheral circulatory failure. One patient received a transplant after 21 days of support, he is well and alive now 1.5 years after the procedure; however, he displays signs of significant psychosomatic disturbances. Two children who were also brought to the operating room under CPR and placed on ECC under cardiac massage were supplied with a biventricular system with left ventricular drainage, 1 with a transmitral tipped cannula, the other with apical cannulation. Both children recovered and displayed a rapid restoration of their cardiac function. When this recovery from myocarditis was found satisfactory, after 11 and 21 days, the system was exchanged for ECMO support of 5 and 6 days, respectively for easier step-wise weaning, after which the patients could be taken off any support. This approach was taken to avoid obstruction of the ascending aorta due to the relatively large VAD cannulae during the weaning process. Both children have since made an excellent recovery and are fully active with an entirely normal heart function after now 2 and 3 years.
A number of aspects encountered during the support period deserve closer description. There was no significant hemolysis detectable during the support period. Two patients suffered cerebral thromboembolism on the device. One (patient 8) had a significant cerebri media infarct which now, 5.5 years after transplant still shows some minor, compensated residuals. This patient had a history of previous cerebrovascular accidents, probably due to thrombusformation in the dilated heart. In another patient (patient 14) signs of less severe cerebral embolism fully disappeared after 6 weeks.
In 5 children, invariably supported by nonheparinized pumps during our earlier experience, thrombi were detected in the blood pumps, requiring repeat pump exchange. Since the time when heparin-coated pumps became available no such instances have reoccurred and there has not been any instance of thromboembolic organ damage.
Bleeding after assist implantation has been the most frequent complication, requiring surgical reexploration in 11 patients.
Except for those patients who died very early from circulatory failure, none of the children suffered de novo infection and, most important, no instance of mediastinitis was observed, not even in the patients with reexplorations.
There was no instance of technical failure, neither of the blood pump components, nor of the drive system.
Recovery of organ function from shock sequelae was quite variable. In particular, no significant differentiation could be made before assist implantation as to the potential of later recovery [17].
Thirteen of the patients on the assist system could be taken off the respirator and were mobilized. Out of this group 11 were transplanted or successfully weaned.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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While the first such applications in children were made at our institution with adult size devices as early as 1990 with long-term survival after subsequent heart transplantation of now 7 years [3], 28 children were supported mostly with the smallest adult pump (50 mL) or with miniaturized pediatric pump systems for up to 98 days since.
Meanwhile other pediatric-type pneumatic systems closely resembling our Berlin Heart model have been introduced into clinical practice with some instances of short-term use [8, 9].
The Berlin Heart system may completely substitute cardiac-output in a monoventricular or, more often, a biventricular configuration [2]. Widely used alternatives are either centrifugal pumps or even ECMO which may sustain the circulation for several days, sometimes a few weeks [4, 10–14]. These systems, apart from a greater damage of blood components and more profound disarray of the coagulation system require continuous intensive care with only a theoretical chance of extubation and mobilization of the patient. But ECMO seems unavoidable when intracardiac shunts persist or when profound respiratory insufficiency accompanies heart failure.
In our hands, ECMO has remained the method of choice for these conditions and for prolonged support of some days after open heart surgery when immediate weaning from the extracorporeal circulation cannot be accomplished and when myocardial recovery can be expected [15].
This mode of treatment has proven successful at our institution, in particular in infants with myocardial impairment such as in Bland-White-Garland syndrome, after switch-operation and total anomalous pulmonary vein drainage [7, 14, 15] and even heart transplantation from ECMO has been successful in complex cardiac defects with shunt after as much as 17 days of support duration in individual cases [15].
Whereas the extracardiac pneumatic blood pump chambers in their miniaturized form, in particular with the inner surfaces now heparin-coated, pose little or no technical problems and complications, cannulae in small children and infants have undergone several modifications. Today a configuration has been reached which seems to be satisfactory and does not necessarily hinder blood flow within the native great vessels of the patient.
The high rate of hemorrhage complications in the assist patients is related to systemic anticoagulation, impaired coagulation in shock, and to the fact that the intrathoracic assist cannulae prevent surface contact of the heart and the intrathoracic structures, a factor which is most important in patients with previous cardiac operations. We have learned that the fibrinolytic activity due to cardiogenic shock allows cautious administration of anticoagulation. The beneficial effect of heparin-coating continued to be present after more than 90 days of VAD use.
The interposition of a flexible polyurethane reservoir into the inflow limb of the small 12 mL pumps has satisfactorily helped sufficient filling of the pump chamber which may otherwise be impaired in cases of high suction pressure [16].
The drive system has not created technical problems as this system has been in routine use in several hundred adult patients for periods of up to 1 years [17].
The overall survival rate in our 28 pediatric patients has been 40%. This result in patients with very advanced disease can certainly be improved in the future and must be looked at in regards to technical development, gathering experiences in treatment of the patients on the device and, most important, with respect to adequate patient selection. The accumulated amount of experience is also documented by the fact that out of the 9 patients supported during 1996 and 1997, 7 have successfully reached transplantation or weaning.
Recovery from profound heart failure and even cardiac arrest has been somewhat better in the children as compared with adults. This is underlined by the surprisingly complete recovery of some patients who were brought to the operating room under chest massage in complete cardiac arrest.
On the other hand, some conditions must be considered unsuitable for implantation of an assist device, at this point of time. All patients in group II, in whom the VAD was implanted after open heart corrective operations and after application of high-dose catecholamines, have eventually succumbed to multiorgan failure or intracerebral hemorrhage. This small patient group was treated during the year 1992. Their condition has since been considered an indication, if at all, for centrifugal pump support or ECMO instead at our institution.
Termination of mechanical support in the face of progressive multiorgan failure and sepsis has opened a new and ethically difficult problem because the mechanical system can supply a patient with a full cardiac output even in a state of extensive tissue damage which otherwise would have caused intractable heart failure. The final observation invariably was a profound loss of peripheral resistance not due to any medication, ie, -receptor stimulants.
Heart transplantation secondary to VAD support initially was considered early after mechanical support was started. As also derived from our adult experience with bridge-to-transplant in up to 108 patients we now would wait long enough to give the patient the chance of full recovery of all organs [2, 16] and of the immune system [18] on the mechanical support device before a state of "transplantability" is declared.
A very exciting experience which opens an entirely new treatment concept has been made with acute myocarditis and untractable heart failure. Whereas in the past, children with this condition have been regarded as bridge-to-transplant candidates, 2 children demonstrated complete and lasting recovery of the heart function after 11 and 21 days of VAD support which then was terminated via ECMO, gradual weaning and final removal of any mechanical system within a few more days. In both these children direct left ventricular drainage and unloading had been applied with the VAD which appears to be mandatory to allow myocardial rest and recovery.
In none of the cases with atrial drainage configuration such impressive recovery was observed. This is in agreement with our experiences in adults with chronic dilated cardiomyopathy in whom we now have explanted LVAD pumps after between 2 and 26 months of support with apical left ventricular drainage [17, 19, 20].
Acute myocarditis, even more so than cardiomyopathy, obviously is, at least in a substantial proportion of the cases, an excellent predisposition to aim for such a recovery.
In conclusion it now seems well established that the beneficial effects of VAD treatment as established in the adult patient group could well be transposed to children of any age when longer support periods are anticipated. Earlier implantation in the course of progressive heart failure now appears to be justified because systems such as the Berlin Heart have undergone the necessary modifications and accumulation of clinical experience which makes the use of this system highly reliable and safe.
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Acknowledgments |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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