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Hypoplastic Left Heart Syndrome: Diagnosis and Early Management
Frederick Jay Fricker
NeoReviews 2008;9;e253-e259
DOI: 10.1542/neo.9-6-e253
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Article
cardiology
Hypoplastic Left Heart
Syndrome: Diagnosis and Early
Management
Frederick Jay Fricker,
MD*
Author Disclosure
Dr Fricker has
disclosed no financial
Objectives
After completing this article, readers should be able to:
1. Describe the morphology of hypoplastic left heart syndrome (HLHS).
2. Recognize clinical findings suggestive of patent ductus arteriosus-dependent systemic
blood flow.
3. Delineate initial postnatal management of HLHS.
4. Describe surgical palliation of HLHS.
relationships relevant
to this article. This
commentary does not
contain a discussion
of an unapproved/
investigative use of a
commercial
product/device.
Abstract
Hypoplastic left heart syndrome (HLHS) is the only congenital heart lesion that
requires the talents of the neonatologist, pediatric cardiologist, and cardiovascular
surgeon operating and communicating as a team to effect the desired outcome of
survival with normal neurodevelopment. Prenatal diagnosis, initial resuscitation, and
preoperative management are key elements that allow the best opportunity for low
surgical morbidity and mortality in the affected infant. Physicians and nurses caring for
such infants must understand the physiology of oxygen delivery and the response of
the neonatal pulmonary and systemic vascular bed to interventions that affect the
balance between systemic and pulmonary blood flow. Outcomes with current surgical
management, including the Norwood procedure and the Sano modification, are
equivalent to those associated with the arterial switch procedure and repair of neonatal
tetralogy of Fallot. Families of infants born with HLHS should be encouraged by the
current results of palliation and long-term outcome.
Introduction
HLHS is a common, potentially lethal congenital heart defect that accounts for a
significant proportion of infant mortality from congenital heart disease in the first year after
birth. This defect has morphologic variability and accounts for 7% to 9% of all infants born
with congenital heart defects. Noonan and Nadas coined the term “hypoplastic left heart
syndrome” in 1958, but Lev described the defect nearly a decade earlier. The defect was
uniformly fatal until 25 years ago, when Norwood performed the first successful palliative
procedure. A number of earlier palliation attempts involved establishing stable systemic
blood flow and restricting pulmonary blood flow, but it was Norwood who persisted and
reported the first survival in early 1980. Surgical modifications by the recent generation of
pediatric congenital heart surgeons have resulted in excellent early survival after the
first-stage Norwood procedure. Paramount to surgical success are early diagnosis and
preoperative management strategies of the neonatologist and pediatric cardiologist. This
review emphasizes findings that create suspicion that an infant has ductus arteriosusdependent systemic blood flow and highlights strategies to balance systemic and pulmonary blood flow until surgery is accomplished.
Morphology
The anatomic features of infants who have HLHS vary, but hypoplasia of the left ventricle
is a consistent finding. The classic phenotype is left ventricular hypoplasia associated with
mitral stenosis/atresia, aortic atresia, coarctation of the aorta, and an intact ventricular
septum (Figs. 1, 2, and 3). Variations include common atrioventricular septal defect with
*Chief of Pediatric Cardiology, University of Florida, Gainesville, Fla.
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cardiology
hypoplastic left heart disease
Figure 1. A cross-section of a heart specimen demonstrating
the key features of hypoplasia of the left heart, including
aortic atresia (A), mitral valve stenosis (MV), and large right
heart. TVⴝtricuspid valve, PAⴝpulmonary valve, coronary
arteriesⴝarrows.
a dominant right ventricle and hypoplasia of the left
ventricle. The ascending aorta and aortic arch have varying degrees of stenosis and hypoplasia (Fig. 3). The
ascending aorta size is a risk factor for surgical palliation.
Aortic atresia with less than 2 mm ascending aorta make
reconstruction of the ascending aorta vulnerable to cor-
Figure 3. Specimen demonstrating aortic atresia with tiny
ascending aorta (Ao) and the presence of discrete coarctation
(arrow) related to insertion of the ductus arteriosus.
AAⴝaortic arch, DAⴝdescending aorta, PDAⴝpatent ductus
arteriosus, RAⴝright atrium.
onary artery obstruction because the ascending aorta is
the only gateway to the coronary circulation (Fig. 1).
Hypoplasia of the transverse aortic arch and isthmus
always is present, with an associated discrete coarctation
Figure 2. Heart specimens with degrees of left heart hypoplasia. Note the increased mass and small cavity of specimen A. In
specimen B, the right ventricle (RV) is large and apex-forming. Note the small mitral valve and left ventricular (LV) cavity size.
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cardiology
hypoplastic left heart disease
(Fig. 3). An unrestricted interatrial communication is
critical to survival. If interatrial communication is intact
or restrictive, the infant will be in extremis shortly after
birth unless the left atrium is decompressed through the
levocardial vein (remnant of the left superior vena cava)
or through coronary artery sinusoids from the left ventricle to the coronary sinus. The right ventricle and
tricuspid valve represent the systemic ventricle and atrioventricular valve, and their functional status determines
the approach to palliation.
Diagnosis
Neonatologists and pediatric cardiologists have witnessed the cardiovascular collapse of an infant who has
patent ductus arteriosus (PDA)-dependent systemic blood
flow. Recovery of end-organ function from the insult of
severe metabolic acidosis and hypoxemia is, at best, slow
and uncertain. Identifying affected infants in a newborn
nursery can be challenging because the ductus arteriosus
remains patent early after birth. Even though infants have
complete admixture of systemic and pulmonary venous
return, pulmonary blood flow relative to marginal systemic
blood flow is increased, resulting in oxygen saturation
greater than 85%. Cyanosis is difficult to recognize at this
level. However, certain clues can increase suspicion of the
presence of a critical heart lesion. Hyperdynamic precordial
activity is a consistent finding that reflects right ventricular
volume and pressure overload. Decrease in amplitude of
peripheral pulses often is cited but is only evident after
ductal constriction in a symptomatic infant. The second
heart sound is single if aortic atresia is present. A heart
murmur of tricuspid valve regurgitation or increased pulmonary blood flow may be audible.
Newborn screening with pulse oximetry has been
advocated. Oxygen saturations rarely are greater than
85% to 88% in affected infants, and decreased saturation
is an indication for cardiology evaluation with echocardiography. Oxygen saturation screening should be undertaken in both the right arm (preductal saturation) and
leg (postductal saturation). Electrocardiography (ECG)
and chest radiography are not adequate ancillary screening methods if the neonatologist suspects a serious congenital heart lesion. Prenatal diagnosis avoids the early
diagnostic and management problems incurred by affected infants and optimizes their outcome.
Initial Postnatal Management
The initial management of infants who have HLHs physiology focuses on safe transport and hemodynamic and
respiratory stabilization. The principal goal is to return
Figure 4. Anatomic heart specimen of aortic atresia demonstrating the course of blood flow from the main pulmonary
artery (PA) through the patent ductus arteriosus (PDA) retrograde into the tiny ascending aorta (double arrows),
DAⴝdescending aorta, RAⴝright atrium.
the infant to the intrauterine state. Re-establishment of
PDA patency and securing the airway is the priority to
re-establish systemic blood flow (Fig. 4). Prostaglandin
E1 (PGE1) is administered at 0.05 to 0.1 mcg/kg per
minute. Because PGE1 can cause apnea initially, the
neonatologist and transport physician should take precautions to secure the airway before transport.
Balancing systemic and pulmonary blood flow to optimize peripheral organ perfusion and function is paramount for successful transition to surgery. PGE1 can
decrease both pulmonary (PVR) and systemic vascular
resistance (SVR); oxygen administration decreases PVR
and increases SVR. Although oxygen administration
while preparing the infant for surgery is potentially detrimental, administration during the resuscitation, stabilization, and transport period can be beneficial. Maintaining oxygen delivery to tissues can be approached by
either decreasing SVR through use of inodilators such as
milrinone or increasing PVR by manipulating the ambient oxygen environment by controlled hypoxia (FiO2 of
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hypoplastic left heart disease
infant who has HLHS is necessary for survival. Restrictive
interatrial communication is analogous to pulmonary
venous obstruction because there is no exit from the left
atrium. Pulmonary venous obstruction results in pulmonary edema, decreased lung compliance, and hypoxemia.
Attempted high-risk interventional septostomy in the
catheterization laboratory can be considered. Urgent
surgery in this clinical setting rarely has a successful
outcome.
100%
85%
75%
Oxygen
Saturation
50%
1:1
2:1
3:1
Qp/Qs Pulmonary blood/Systemic blood flow
Figure 5. Effect of increasing oxygen saturation on the ratio
of pulmonary blood flow to systemic blood flow.
17% to 20%) or by hypoventilation resulting in hypercarbia. Milrinone is both an inotropic drug and an effective
systemic vasodilator agent (phosphodiesterase inhibitor)
that is used in the preoperative management of infants
who have HLHS. One other point should be emphasized
regarding oxygen administration. The diagnosis should
be confirmed before discontinuing oxygen because a
missed diagnosis of persistent pulmonary hypertension of
the newborn is lethal.
The relationship between pulmonary blood flow and
systemic blood flow is assessed by clinical examination
and oxygen saturation/arterial blood gas determinations. The oxygen saturation trend is key to day-to-day
management and to evaluating an acute change in the
infant’s clinical condition. Because HLHS is a complete
admixture lesion (complete mixing of systemic and pulmonary venous return), the relative pulmonary blood
flow (QP)-to-systemic blood flow (QS) ratio is determined by assessing changes in systemic oxygen saturation
through pulse oximetry or arterial blood gas changes.
A balanced QP/QS saturation is 75% QP/QS 1:1. Because PVR is lower than SVR, the oxygen saturation for
infant who has HLHS in a stable balanced hemodynamic
state should range from 75% to 85%. As PVR decreases
and the QP/QS ratio increases, the oxygen saturation/
arterial PO2 increases (Fig. 5). If PGE1 administration is
interrupted and the ductus arteriosus constricts, QS relative to QP decreases, a marked increase in oxygen
saturation and arterial PO2 occurs, and metabolic acidosis
develops. Oxygen saturation falling below 70% should
raise concern about lung atelectasis or restriction of the
interatrial communication causing a decrease in QP relative to QS. Communication at the interatrial level in the
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HLHS Surgery
In 1980, Norwood and colleagues were the first to
describe neonatal palliation that eventually leads to the
staged Fontan (atrial-to-pulmonary connection) approach for infants who have single-ventricle physiology.
The conventional Norwood procedure must provide unrestricted systemic blood flow by reconstructing the aortic arch, a widely patent interatrial septum, and a source
of pulmonary blood flow. Early favorable outcome depends on such preoperative variables as the size of the
ascending aorta (preferable situation is prograde flow
through the ascending aorta) and good right ventricular
and tricuspid valve function.
Reconstruction of the ascending aorta and aortic arch
require incorporation of the main pulmonary artery and
patch augmentation of the aortic arch with homograft
material to relieve the associated coarctation completely.
The new source of pulmonary blood flow in the modified
Norwood operation was a 3.0 to 3.5 Gortex威 central
shunt between the right innominate artery and the right
pulmonary artery. Systemic-to-pulmonary shunt failure
and postoperative difficulty managing pulmonary blood
flow led to the resurgence of the Sano modification. This
modification uses a right ventricle (RV)-to-pulmonary
artery (PA) conduit instead of a central systemic-topulmonary artery shunt. The RV-to-PA conduit results
in higher systemic diastolic pressure and better coronary
artery perfusion. A multicenter trial is evaluating the
central shunt versus Sano modification in terms of perioperative and late morbidity and mortality. The other
evolving area of study is the management of cerebral
perfusion during aortic arch reconstruction. This operation is performed during a period of deep hypothermic
circulatory arrest. Concern for long-term neurologic sequelae has stimulated the development of techniques to
eliminate deep hypothermic circulatory arrest. Techniques for maintaining continuous cerebral perfusion are
now part of intraoperative management.
Advances in critical care and postoperative management have played major roles in improving outcomes.
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cardiology
The availability of mechanical/oxygenation support
(extracorporeal membrane oxygenation) is mandatory in
centers that perform such procedures. The most important factor is the availability of a multidisciplinary team
around the clock for these complex patients.
HLHS Heart Transplant
The Norwood procedure is offered to most patients who
have HLHS. Neonatal heart transplant was pioneered by
Bailey and Loma Linda University for infants who have
HLHS. Although transplantation would be the preferred
palliation, donor heart availability limits its use. Centers
that recommended heart transplantation have reported a
30% mortality rate among infants waiting for donor
hearts. This factor made it clear that the infants who have
HLHS and are good Norwood candidates should be
referred for a single-ventricle surgical approach. Infants
who have tiny ascending aortas or right ventricular dysfunction and severe atrioventricular valve regurgitation
should be referred for heart transplantation.
hypoplastic left heart disease
flow, and factors controlling initial formation of the left
atrioventricular junction, have been inferred from chick
model experiments. It is likely that multiple causes contribute to HLHS.
Prenatal diagnosis has had a major favorable impact
on both survival and neurologic outcome. In addition,
prenatal diagnosis affords the opportunity for counseling
with neonatology and cardiology. Finally, prenatal diagnosis has allowed attempts at in utero treatment of
hypoplasia of the left ventricle by balloon dilatation of
critical aortic stenosis. However, the group of infants
amenable to this treatment represent only a small subset
of those born with HLHS.
ACKNOWLEDGMENT. Morphology photographs are
from the Van Mierop Collection at University of Florida.
Courtesy of Diane Spicer.
Suggested Reading
Comfort Care
The offer of no intervention to a family for an infant who
is a candidate for single-ventricle palliation remains controversial. Although neonatologists and pediatric cardiologists review with families the diagnosis, prognosis,
and potential long-term issues related to single-ventricle
palliation, it is the unusual family that chooses no intervention. The current surgical outcomes for infants who
experience excellent hemodynamic repair and maintain
normal developmental landmarks makes it difficult not to
encourage families to pursue care in spite of an uncertain
future.
Advances in Understanding and Treatment
Although congenital heart disease remains the leading
cause of death from congenital malformations, advances
in neonatal surgery, accurate fetal diagnosis, and improving neonatal management have resulted in increased
survival. In fact, there are now more patients who have
congenital heart disease older than age 18 years than
there are younger patients. HLHS causes significant
mortality from birth to age 3 years, when all of the
palliative procedures are completed. The cause of HLHS
still has not been identified. The condition is reported in
families, and the diagnosis is associated with other genetic chromosomal abnormalities, including Turner syndrome. Hemodynamic causes, including abnormalities
of atrial septum development, intrauterine cardiac blood
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NeoReviews Quiz
5. The classic phenotype of hypoplastic left heart syndrome (HLHS) includes left ventricular hypoplasia
associated with mitral stenosis/atresia, aortic atresia, coarctation of aorta, and an intact ventricular septum.
Of the following, the most accurate statement regarding HLHS is that:
A.
B.
C.
D.
E.
An intact interatrial septum is critical for survival.
Functional status of the right ventricle determines the approach to palliation.
HLHS accounts for approximately 25% of all cases of congenital heart disease.
Left ventricular communication with coronary sinusoids worsens the prognosis.
The size of the descending aorta is a risk factor for surgical palliation.
6. You suspect that a 6-hour-old term newborn has HLHS. Of the following, the most consistent clinical
finding in this infant would be:
A.
B.
C.
D.
E.
Decreased amplitude of peripheral pulses.
Ductal systolic heart murmur.
Hyperdynamic precordial activity.
Severe cyanosis.
Split second heart sound.
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hypoplastic left heart disease
7. In the initial stabilization of a newborn who has HLHS, attention to balancing the systemic and pulmonary
blood flow is critical for successful transition to surgery. Of the following, the initial step in the
management of HLHS is the administration of:
A.
B.
C.
D.
E.
Inhaled nitric oxide.
Mechanical hyperventilation.
Phosphodiesterase inhibitor milrinone.
Prostaglandin E1 infusion.
Subatmospheric oxygen.
8. Management of HLHS has evolved over the last 3 decades. Of the following, the current approach to
management of HLHS in most infants is:
A.
B.
C.
D.
E.
Blalock-Taussig shunt.
Comfort care.
Glenn shunt procedure.
Neonatal heart transplantation.
Norwood palliation.
NeoReviews Vol.9 No.6 June 2008 e259
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Hypoplastic Left Heart Syndrome: Diagnosis and Early Management
Frederick Jay Fricker
NeoReviews 2008;9;e253-e259
DOI: 10.1542/neo.9-6-e253
Updated Information
& Services
including high-resolution figures, can be found at:
http://neoreviews.aappublications.org/cgi/content/full/neoreview
s;9/6/e253
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