1. Indian Heart J 2006; 58: 345–349 345
Seminar
INTRODUCTION
Acute heart failure commonly occurs in children as a result
of hemodynamic insults imposed on the heart by structural
defects or in a structurally normal heart with myocarditis.
Aggressive treatment of even the most complex congenital
heart disease (CHD) is being championed with ever-improv-
ing results. Despite good repair, these patients go through
various periods of refractory low cardiac output and form an
expanding substrate for short-term mechanical support.
Various indications for pediatric mechanical support are
enumerated in Table 1. When present, acute heart failure in
children justifies aggressive therapy because of the high
potential for complete recovery. Extracorporeal life support
organization (ELSO) data stands testimony to this.1
The
international summary for patients on extracorporeal life
support (ECLS) for cardiac failure showed that 57% of
neonates and 58% of pediatric patients survive ECLS with
38% of neonates and 43% of pediatric patients surviving to
hospital discharge or transfer.
Achieving circulatory support in the pediatric practice is
confounded by the wide range of patient size, the small size
and fragility of the vasculature along with significant
anatomic variations which may affect cannulation. Finally,
heart failure in the pediatric population is often biventricu-
lar and is commonly associated with pulmonary dysfunc-
tion. The rationale for use of and the devices available for
circulatory support are discussed.
Why Mechanical Support?
Long bypass and aortic cross-clamp ischemia along with an
exaggerated inflammatory response for complex cardiac
defects, leads to myocardial incompetence presenting as
low cardiac output. Further, because of a labile and reactive
pulmonary bed, the right ventricle is subjected to variable
decrease of after-load excesses, which displaces the inter-
ventricular septum to the left impairing left ventricular
filling and systolic functions. Post-cardiopulmonary bypass
(Post-CPB), cyanotic hearts also tend to be more edema-
tous, which impacts coronary perfusion and diastolic and
systolic functions.
This reperfusion-insulted and energy-depleted stunned
myocardium has the potential to recover if given the right
support. Unfortunately instinctive support is provided by
increasing dosages of pharmacological agents, which
further aggravate the myocardial injury. Catecholamines
cause variable increase in after-load excesses and tachycar-
dia and increase in contractility leading to an increase in
myocardial oxygen demand at a time when supply may be
sub-optimal due to low pressure and increased transmy-
ocardial gradients. Thus energy stores which are needed for
myocardial repair and maintenance of ionic homeostasis are
expended in contractile work which can result in signifi-
cant ongoing myocardial injury that may compromise or
prevent cardiac injury. On the other hand, mechanical
support reduces myocardial work thereby preserving
energy stores and at the same time it maximizes myocardial
delivery. Most devices unload the heart which reduces the
Mechanical Circulatory Support for Acute Cardiac Failure in Children:
The Options Available
Sathiakar Paul Collison, Kulbhushan Singh Dagar
Department of Neonatal, Pediatric and Congenital Heart Surgery, Escorts Heart Institute
and Research Centre, New Delhi
Correspondence: Dr Kulbhushan Singh Dagar, Escorts Heart Institute and Research Centre, Okhla Road, New Delhi
E-mail: dagarks@hotmail.com
Table 1. Indications for ventricular assist
No cardiotomy
Acute changes in congenital heart disease patients
Acute myocarditis
Decompensated cardiomyopathy (“Bridge to transplant”)
Salvage for cardiac arrest
Management of intractable destabilizing arrhythmias
Hypoxia, destabilizing pulmonary hypertensive crises
Post-surgical repair
CPB-induced
Bridge to recovery post-CPB (e.g., late arterial switch,
ALCAPA repair)
CPB: cardiopulmonary bypass; ALCAPA: anomalous origin of the left coro-
nary artery from the pulmonary artery.
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2. wall stress, thereby reducing the oxygen demand, and also
improves sub-endocardial perfusion.
When to Initiate Support
Mechanical support is a better methodology for myocardial
support and resuscitation in hearts refractory to usual levels
of pharmacological support. As with most forms of support,
results may be directly related to the threshold at which
support is initiated. In some series, survival has been found
to be greater when ECLS is instituted some time after
successful weaning from CPB.2
However, Aharon et al.
reported that the initiation of ECLS in the operation theatre
for failure to wean from CPB was associated with better
survival.3
More recently Chaturvedi et al. showed that odds
of survival were improved if there was initiation of extra-
corporeal membrane oxygenation (ECMO) in the theatre
(64% survival) rather than in the cardiac intensive unit
(29% survival).4
The results may be confounding because
of different patient subsets and ideologies. However, it is
amply clear that if anatomic correction is adequate, early
and appropriate support before end-organ injury, severe
metabolic derangement occurrence or cardiac arrest can
lead to excellent results.
INTRA-AORTIC BALLOON
COUNTERPULSATION
The intra-aortic balloon pump (IABP) is a non-flow generat-
ing counter pulsation type of assist. Intra-aortic balloon pump
deflation in systole leads to reduced ventricular after-load and
ventricular wall stress, thereby improving cardiac perform-
ance. Inflation of the balloon in diastole increases the aortic
diastolic pressure and hence coronary perfusion and distal
runoff (Figure 1). Appreciable measure of the patient’s own
cardiac function must be present and the IABP augments this
improving cardiac output to the tune of 15–20%. Hence IABP
is a poor form of support for total replacement of the function
of a ventricle. It is extensively used in the adults where it is a
good form of support for coronary flow augmentation.
Intra-aortic balloon pump usage in a pediatric popula-
tion was first described in 1980s.5
However, its application
in children has not been widespread for the following
reasons. Unlike adults, an open surgical insertion of the
balloon is employed in children.6
The criterion used in
selecting a catheter of an appropriate size has been detailed
elsewhere.7
Timing of the balloon may be performed by
using either electrocardiography tracing or echocardiogra-
phy. Recent reports emphasized M-mode echocardiography
as the tool to ensure proper timing of balloon inflation and
deflation.8
There are also concerns regarding the efficacy of
using the IABP in the pediatric population with its high
incidence of arrhythmias making optimal timing very diffi-
cult. The aorta in children is thought to have greater elastic-
ity than that in adults. Hence, much of the energy generated
during balloon filling may be transferred to the expansile
aorta and diastolic augmentation may be dampened.
However, the effect of IABP on systolic unloading of the
left ventricle is preserved. Children frequently present with
right ventricular failure with or without respiratory failure,
both of which cannot be supported by IABP. Hence the role
of IABP in pediatric patients is at best restrictive and prob-
ably limited to support of isolated left heart failure for short
duration.
In Pollock’s study, which is the earliest experience of
IABP use in children, there was a 43% survival among a
group of 14 children.5
Webster and Veasy reported the use
of IABP in patients aged between 5 days to 18 years; the
smallest child weighed 4.2kg.9
The survival in children
aged below 3 years was 75%. Park et al. studied children
with left ventricular dysfunction after cardiac surgery and
reported 44% survival among those managed with IABP.10
Del Nido et al. reported the successful utilization of IABP
support in a 2- kg infant.11
In their series of patients, 37%
were long-term survivors. Much of the understanding of the
contemporary role of IABP usage and results (Table 2) for
Collison and Dagar
346 Indian Heart J 2006; 58: 345–349
Figure 1. Depiction of the aortic systolic and diastolic pressures
during a normal cardiac cycle as well as an augmented beat.
Table 2. Results of IABP use among individual patient groups
Disease Number Survival (%)
Medical Cardiomyopathy 8 50
Myocarditis 2 100
HUS 1 100
Blunt trauma 2 100
Surgical ALCAPA 3 100
Fontan 2 100
TOF 3 0
VSD 4 50
Complex conduit repair 4 50
IABP: intra-aortic balloon pulsation; HUS: hemolytic uremic syndrome;
ALCAPA: anomalous left coronary artery from pulmonary artery; TOF: tetral-
ogy of fallot; VSD: ventricular septal defect.
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3. temporary mechanical cardiac support in children has come
from Pinkey et al.12
Poor results in tetralogy emphasize
limitations of IABP in biventricular or predominant right-
sided support.
EXTRACORPOREAL MEMBRANE
OXYGENATION (ECMO)
In veno-arterial ECMO (VA-ECMO), the functions of heart
and lungs can be partially or totally replaced. A typical
ECMO circuit is depicted in Figure 2. Deoxygenated blood
is drained from the right atrium through cannula inserted
into the internal jugular vein and the blood that has been
oxygenated extracorporeally is pumped back into the right
common carotid artery, allowing total cardiopulmonary
support. Thus, the heart and lung can be bypassed and
hence rested, allowing time for the heart to heal in an envi-
ronment of normal systemic perfusion and gas exchange. It
is this flexibility of the ECMO circuit that makes ECMO
versatile in supporting children with acute cardiac failure,
where hypoxia, pulmonary hypertension, ventricular failure
and cyanosis all contribute to the pathophysiology of acute
cardiac failure. It is advisable to maintain moderate levels
of ventilator support during ECMO.13
Avoidance of left
ventricular distention is essential. When detected, left-sided
decompression is achieved by balloon atrial septostomy
performed at the bedside under echocardiography guid-
ance,14
or surgical insertion of a left ventricular vent.
Several studies provide the rationale for the use of ECMO
for circulatory support in children.15-25
The central tenets
of successful cardiac ECMO are enumerated in Table 3.
Besides, any child with cardiac disease who requires increas-
ing ventilation or escalating dosages of inotropes with
persistent borderline cardiac output and evidence of end-
organ failure must be considered for ECMO support. Several
studies showed the benefit of early institution of ECMO
support over delayed support. Institution of ECMO is
contraindicated in the presence of incurable malignancy,
advanced multi-systemic organ failure, extreme pre-maturity
and severe central nervous system damage.
Several centers reported consistent results of ECMO for
cardiac failure in children. Overall the weaning rate is
50–80% and hospital survival is 30–70% depending on the
underlying diagnoses. In general, two-thirds of patients can
be weaned off ECMO and 40% of the original population
will eventually survive to hospital discharge.15-25
Table 4
gives details of the results of ECMO, as derived from the
ELSO registry.1
Special mention must be made of the emerging role of
ECMO in patients with fulminant viral myocarditis. This is
an entity that is extremely difficult to manage and affected
children have a guarded prognosis. It was believed that a
significant percentage of children with acute myocarditis
would develop dilated cardiomyopathy, ultimately needing
cardiac transplantation. However, current data suggest that
the survival rate for children with acute myocarditis can be
improved by using ECMO.26,27
The ELSO data suggest that
58% of these patients can be weaned off the support.
Another recent multi-centric study reported an overall
survival of 80%.28
An important finding of this study was
that all non-transplanted survivors were alive with normal
ventricular function suggesting that children with acute
myocarditis, if successfully supported during the acute
phase of the illness, may have an overall favorable outcome.
Mechanical Circulatory Support for Acute Cardiac Failure in Children
Indian Heart J 2006; 58: 345–349 347
Figure 2. Depiction of a typical veno-arterial ECMO circuit.
ECMO: Extracorporeal membrane oxygenation.
Table 3. Pre-requisites for cardiac ECMO
Potential for myocardial recovery should exist
Adequate anatomic repair without residual lesions
Appropriately managed associated reversible factors, such
as pulmonary hypertensive crises and post-operative
myocardial edema
The timing of initiation of ECMO in a controlled fashion
before circulatory collapse is essential in preventing
organ injury
ECMO: extracorporeal membrane oxygenation.
Table 4. Survival of patients undergoing ECMO for cardiac
diseases*
Diagnosis Percentage survived
Medical Cardiomyopathy 50
Myocarditis 58
Surgical Left to right → R shunt 41
Left-sided obstruction 30
Right-sided obstruction 43
Hypoplastic left heart 32
Cyanotic, increased Qp 40
(TGA)
Cyanotic, decreased Qp 40
(tetralogy)
*Data from extracorporeal life support organization registry.
ECMO: extracorporeal membrane oxygenation; TGA: transposition of the
great arteries.
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4. The need for continued ventilation in an intensive care
setting and constraints related to trained manpower and
obvious financial implications prevented its widespread use
in India. Also, when it is expected that recovery will take
longer than a week, the ventricular assist devices (VADs)
have an obvious advantage over ECMO.
VENTRICULAR ASSIST DEVICES
Ventricular assist devices are mechanical pumps that can
perform the function of either one or both of the ventricles,
restoring perfusion and maintaining end-organ function,
while the heart recovers from the precipitating insult.29
The
different types of devices available are detailed in Table 5.
Ventricular assist devices may be required for right ventric-
ular support (RVAD) or for left ventricular support (LVAD).
For an LVAD, a Dacron tube graft is inserted into the left
ventricular (LV) apex or pulmonary vein and connected to
the pump (afferent limb). From the pump, blood is ejected
through a Dacron graft into the descending aorta (efferent
limb). To maintain unidirectional flow, prosthetic valves are
incorporated into both limbs of the circuit. For an RVAD,
usually the right articular appendage and the main
pulmonary artery are cannulated to create the circuit.
Implantation is generally done without CPB, and can be
performed either through a median sternotomy or by lateral
thoracotomy. Infection, thromboembolic events, bleeding
and neurological complications are common. Right-sided
circulatory failure can occur in patients supported by an
LVAD in 10–15% cases. In spite of optimization of all
parameters, the right-sided failure persists. This is an indi-
cation for the addition of RVAD.
The most commonly used centrifugal device is the para-
corporeal Bio-Medicus pump.30
For infants weighing less
than 10kg, a 50-ml pump is available; for other children, an
80-ml pump is available. The cannulation required is stan-
dard, and as described above, this system can provide
support to the right ventricle as well as the left ventricle.
Karl et al. reported 34 patients with a median age of 60 days
and median weight of 3.7 kg;31
LVAD using a centrifugal
device allowed 24–45% survival in these patients. The
youngest patient in whom the Bio-Medicus pump has been
placed was two days of age and weighed 1.9kg.
Pulsatile devices can be located at the bedside, para-
corporeally, or may be implantable. These devices,
however, can only be used in adolescents with adequate
body surface area (BSA) typically >1.5m2
for implantable,
and at least > 0.7m2
for paracoporeal devices. Merkle et al.
have reported on 45 pediatric patients supported by the
Berlin Heart which is the commonest device used in chil-
dren.32
Of these, there was 70% survival after separation
from the VAD, with long-term survival in 56%. Hetzer
et al. used the Berlin Heart system for various indications;
the survival rate was 40%.33
The main constraint of VAD in
children is the limited space available in the child’s thoracic
cavity for these devices, especially in cases requiring biven-
tricular support and hence needing four cannulae. However,
the Berlin Heart has been used successfully for biventricu-
lar support. The results of Medos VAD have been comparable
with the Berlin Heart. Konertz et al. managed 12 children
with ages between 8 hours and 25 days.33
In their study, the
survival for LVAD use was 80% and for RVAD use was
33%. Goldman et al. studied children undergoing bridge to
transplantation with the Medos VAD. Fifty-five percent
eventually survived transplantation.35
Axial pumps generally consist of electromagnetically
coupled, integrated motor-impeller pump assemblies.36
Depending on size, flows up to 3.3 L/min can be achieved.
The Jarvik 2000 is approved for implantation in patients
with a BSA of 1–1.5 m2
, but so far there has not been any
implantation in a pediatric patient.37
The MicroMed
Debakey VAD is approved by FDA in USA for use in
patients aged between 5–16 years, and can be placed in
children with a BSA as low as 0.7m2
.38
Mechanical circulatory support in children will play an
ever increasingly important role in the future practice of
congenital cardiac surgery. If their full potential is to be
utilized, their early use should be integrated into the deci-
sion-making cascade for low cardiac output, rather than
being relegated to the realm of rescue therapy. More
aggressive and earlier implementation of support will lead
to superior outcomes. As of today, arteriovenous ECMO
holds promise because of its flexibility of use in different
age groups and its ability to provide biventricular support
along with respiratory support. Its use beyond 5–7 days is
associated with poor results. Slow recovery should prompt
consideration of switch to VAD as bridge to further recov-
ery or transplantation in patients with BSA >0.7 m2
. With
miniaturization, axial flow pumps probably hold great
promise for pediatric patients. Centrifugal pumps and IABP
may have a role for isolated short-term support of the
failing ventricle like after ALCAPA (anomalous origin of
the left coronary artery from the pulmonary artery) repair
or late arterial switch operation. The use of IABP would
continue to be anecdotal in pediatric cardiac practice.
Devices exclusively for pediatric use like the Pedia Flow
VAD (University of Pittsburg), Ensions p CAS, the Pediatric
Collison and Dagar
348 Indian Heart J 2006; 58: 345–349
Table 5. Ventricular assist devices (VADs)
Device Examples
Centrifugal assist devices Medtronic Bio-Medicus pump
Axial flow pumps MicroMed Debakey VAD,
Pediatric Jarvic 2000
Pulsatile
Paracorporeal Berlin Heart VAD, Medos
HIA VAD
Implantable Thoratec VAD, Heartmate VAD
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5. Jarvik 200039
are under various stages of development and
hold great promise for the future.
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