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Heart Failure in Children

Background

Heart failure is the final, common pathway of a complex

interplay of structural, functional, and biologic factors thatlead to cardiac pump and circulatory system dysfunction. Such

factors result in an inability of the heart to keep up with the

metabolic demands of the body. In contrast to adults in whom

ischemic heart disease is the most common etiology of heart

failure, in children, a range of defects, including congenital heart

defects, systemic metabolic disorders that affect the myocardium,

tachyarrhythmias, and acquired heart disease can cause heart

failure to develop.

Recent advances in the medical and surgical management of

heart failure have improved the morbidity and mortality ofheart failure in the pediatric population. Additionally, recent

advances in heart failure management have improved survival

rates for patients who develop end stage heart failure that requires

cardiac transplantation. This article will serve as an overview

of the physiology, etiologies, clinical presentation, diagnosis and

management of heart failure in children.

Pathophysiology

The symptoms, known as heart failure (HF), are the final

pathways that occur when the hemodynamic demands on theheart exceed the pressure- or flow-generating capacity of the

systemic pump. Such might be secondary to either inadequate

inflow or inadequate outflow. Limited inflow (diastolic

capacity) is prevalent in disorders such as pericardial disease,

restrictive cardiomyopathy, mitral stenosis or pulmonary-

venous obstruction. Limited outflow (systolic capacity) has

characteristics of disorders that include dilated cardiomyopathy,

prolonged tachyarrhythmias and systemic-outflow obstruction.

HF might occur when normal hemodynamic demands are

imposed on myocardium with decreased systolic or diastolic

function, when an excess load is imposed on normal myocardium,

or when a combination of the two occurs. To determine

appropriate management, the practitioner must identify the

presence or absence of congenital heart defects and of myocardialdysfunction. For most types of congenital heart disease, repair or

palliation of the underlying structural defect provides the most

definitive improvement; whereas medical management of the HF

symptoms might not be adequate. If the HF is secondary to non-

myocardial factors, such as hematologic, metabolic, endocrine or

renal disease, therapy is rarely successful unless the underlying

etiology also is treated.

At the basic biologic level, there is a complex interplay of

neurohormonal factors that occur in response to heart failure, to

meet the hemodynamic demands of the body. At the tissue level,when regional flow is inadequate, there is a rise in metabolite

concentrations such as ADP, which stimulate local vasodilation.

Such allows flow to increase and metabolites to be removed. The

vasodilation produces a decrease in peripheral vascular resistance

and systemic blood pressure, which results in improved cardiac

output.

There are baroreceptors within the vasculature that respond

to the fall in pressure by stimulating reflex mechanisms,

including the sympathetic nervous system (SNS) and the renin-

angiotensisn-aldosterone system (RAAS). The SNS providesthe rapid response to the failing heart: tachycardia, stimulation

of myocardial contractility, and regional vasoconstriction. The

RAAS pathway provides longer term response by stimulating

renal fluid retention to expand vascular volume, thus improving

cardiac filling and restoring cardiac output. Under normal

conditions, these mechanisms work to maintain normal blood

pressure, cardiac output and volume. When the fall in cardiac

output and blood pressure are due to diminished cardiac

contractility, these same mechanisms might prove detrimental to

the failing myocardium. Chronic activation of the SNS causes

persistent tachycardia, which shortens diastole, thus decreases

coronary blood flow while vasoconstriction increases the cardiac

workload by increasing afterload. Volume expansion caused by

chronic activation of the RAAS system might cause pulmonary

edema or hepatic congestion in the presence of systolic or diastolic

cardiac dysfunction. In addition to the activation of the SNS

and RAAS systems, increased release of vasopressin, endothelin,

and inflammatory cytokines also occur during congestive

heart failure. The long term consequences of these maladaptive

mechanisms are still being studied but are thought to play a role

U N I V E R S I T Y O F M I N N E S O T A A M p l A T z C H I l D R E N S H O S p I T A l

Elizabeth Braunlin, M.D.Rebecca Ameduri, M.D.


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to evaluate atrial and ventricular size, pulmonary artery pressu

and cardiac function.

Older infants and children with heart failure have signs and

symptoms similar to those of adults. Children might have

shortness of breath with dyspnea that is exaggerated by exerci

A chronic cough secondary to pulmonary congestion might bpresent. Symptoms of congestive heart failure in children mig

be subtle but often an intercurrent illness will be enough to

exacerbate the underlying hemodynamic abnormalities and al

congestive heart failure to become apparent.

Fatigue and weakness are late findings. On physical examinat

children with mild to moderate heart failure might not appea

in distress; however, children with more severe heart failure

might demonstrate dyspnea and tachypnea at rest. A child or

adolescent, who cannot speak in full sentences, is on the verge

cardiorespiratory failure.

Children with chronic heart failure sometimes appear

malnourished and pale. Distention of the neck veins can be

difficult to appreciate but reveals increased systemic venous

pressure. Hepatomegaly is typically present and if the heart

failure is acute in nature, associated flank pain might occur as

a result of stretching of the liver capsule. Once an increase in

body weight oocurs - approximately 10 percent - the child mi

develop peripheral edema in dependent parts of the body. In

more severe cases, children might develop ascites, pleural and

pericardial effusions. Occasionally, presacral edema is seen in

young as well as elderly recumbent persons in heart failure.

Cardiac exam is variable depending on the etiology and presen

of congenital heart disease. A murmur might be audible from

large systemic to pulmonary shunt or from atrioventricular va

regurgitation. A gallop heart sound with a third and possibly a

fourth heart sound might be heard. Palpation of the chest can

reveal a laterally displaced or diffuse apical impulse, and a rig

ventricular heave.

The diagnosis of heart failure is sometimes made serendipitou

by ordering a chest X-ray for other reasons. The chest X-rayin congestive heart failure typically shows cardiomegaly and

interstitial pulmonary edema, which, in more severe cases, cau

diffusely hazy lung fields. Cardiac ultrasound is the primary

modality for defining the cardiac anatomy and for assessing

ventricular function in children with heart failure. Although

initial diagnosis of congenital heart disease in an older child

is rare, some children who have undergone previous palliative

surgeries for congenital heart disease may later develop heart

failure several years after the palliation.

in the adverse remodeling of the myocardium and vasculature that

occurs in chronic heart failure. The overall net effect is an increased

systemic vascular resistance and increased myocardial fiber length

classically described by Starling.

Clinical Presentation

Four cardinal signs of heart failure in children Tachypnea Tachycardia

Cardiomegaly Hepatomegaly

The signs and symptoms of heart failure vary depending on the age

at presentation and the underlying etiology. The clinical findings

are different in infants versus older children and adolescents.

Infants with heart failure typically present with feeding difficulties

as this is one of their most demanding physical activities. Theymight take more time to feed and have associated tachypnea,

tachycardia and diaphoresis. Growth failure is a classic feature in

infants with congestive heart failure. Alternatively, infants who

have chronic cough that are unresponsive to typical respiratory

therapies might be exhibiting signs of heart failure.

Physical examination of infants with heart failure will reveal resting

tachycardia and tachypnea. As HF symptoms progress, they might

develop signs of respiratory insufficiency including nasal flaring,

retractions, and grunting. The cardiac exam is variable, depending

on the etiology of heart failure. Murmurs might be present. Infantswith cardiomyopathy might have a mitral regurgitation murmur

and a third heart sound. The third heart sound, however, may be

difficult to appreciate with the rapid heart rate. Infants with HF

will have hepatomegaly associated with increased systemic venous

pressure and/or volume. Peripheral edema is rare in infants.

With severe heart failure and low cardiac output, infants might

have cool extremities, weak pulses, low blood pressure, mottling

of the skin and delayed capillary refill. A chest X-ray will typically

show cardiomegaly. Most infants with HF have some degree of

pulmonary venous congestion, which appears as a diffuse hazinesson the chest X-ray. Infants with large systemic to pulmonary

shunts show increased pulmonary vascular markings. Although

an electrocardiogram might be abnormal and provide clues to

the diagnosis, such as the presence of Wolff-Parkinson-White

syndrome, it does not usually help in defining heart failure severity.

Cardiac ultrasound provides the most useful information in the

evaluation of infants with heart failure. The imaging defines the

underlying cardiac anatomy. The imaging also allows practitioners



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Etiologies

There is a wide spectrum of etiologies that can lead to heart

failure in children. Tables 1 and 2 summarize the more common

etiologies of heart failure in pediatrics, organized by the presence

of a structurally normal heart (Table 1) or the presence of

congenital heart disease (Table 2).

Among the more common causes of congestive heart failure likel

to present to the primary-care physician are myocarditis and

idiopathic dilated cardiomyopathy. Additionally, patients who

have had prior repair or palliation of congenital heart disease

might present in adolescence or adulthood with signs of heart

failure. See below for more detail.

Patients with myocarditis might present with a febrile illness and

have generalized viral symptoms, including upper respiratory

symptoms, vomiting and diarrhea. Myocarditis might be presentif a child has tachypnea and/or tachycardia that are out of

proportion to the severity of illness, or have key physical findings

such as hepatomegaly, a third heart sound, new onset of murmur

of mitral regurgitation, pericardial friction rub or distant heart

sounds. In this setting, a chest X-ray is useful to evaluate cardiac

size and presence of pulmonary edema. Patients should receive a

referral for an urgent evaluation by a pediatric cardiologist. The

immediate evaluation is necessary because the patient might have

rapidly progressive deterioration in status over the course of a few

hours.

In patients who have severe myocarditis, approximately one-

third of them will have recovery of normal cardiac function,

one-third will continue to have compromised function but will

remain stable over time, and one-third will have a progressive

decline resulting in either death, need for mechanical circulatory

support or transplantation. However, the advent of ventricular-

assist devices for pediatric use have introduced a new, natural

history for myocarditis in which some patients who would

have previously died are able to receive support long enough to

recovery myocardial function.

Patients with idiopathic dilated cardiomyopathy can be

relatively asymptomatic until cardiac function becomes severely

compromised and signs of HF develop. On careful history, the

patient will typically report a decreased exercise tolerance and

increasing fatigue before the overt appearance of HF symptoms.

Additionally, such patients can be well compensated despite their

decreased function until an additional stress, such as a viral or

bacterial infection, imposes on them. Figure 1 demonstrates an

H E A R T F A I l U R E I N C H I l D R E N

Figure 2.Cardiomyopathy Evaluation

Chest X-ray, EKG,

Echocardiogram

Viral Studies

Cardiac MRI

Endomyocardial Biopsy

Family History

Initial blood/urine to evaluate

for metabolic and mitochondrial

diseases Genetics and

Neuromuscular consults

Dilated cardiomyopathy:

Consider karyotype,

familial dilated cardiomyopathy

gene chip, mitochondrial DNA

sequencing, skeletal and/or

endomyocardial biopsy

Hypertrophic cardiomyopathy:

Consider karyotype,

familial hypertrophic

cardiomyopathy

gene chip, mitochondrial

DNA sequencing, screening

for Noonan syndrome,

skeletal and/or

endomyocardial biopsy

YES NOSuspect Myocarditis

Figure 1.Echocardiogram pictures of normal heart versus

patient with dilated cardiomyopathy. Four chamber view of a

normal heart (A) and a patient with dilated cardiomyopathy (B)

Short axis and m-mode demonstrating normal contractility (C)

versus dilation and decreased function (D).


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Cardiac ultrasound, 12-lead electrocardiogram, and chest X-ray

are standard for the initial workup. Cardiac ultrasound is the

most useful tool for evaluation of congenital heart disease and

ventricular function. Standard laboratory evaluation includes

thyroid-function testing, hemoglobin and carnitine levels.

Additionally, patients typically undergo laboratory assessment of

the severity of heart failure by measurement of brain-anatriuretic

peptide (BNP), troponin, and by evaluation for markers of renal

and hepatic end-organ dysfunction.

In the absence of structural cardiac disease, evidence for

myocarditis is sought by viral culture and polymerase chain

reaction (PCR) analysis. Genomic testing of the more common

forms of familial dilated cardiomyopathy is indicated if a first-

degree relative has a cardiomyopathy. Urine organic acids and

serum amino acids are tested to rule out the possibility of

metabolic disorders. Skeletal muscle biopsy can be obtained if

there is suspicion of systemic mitochondrial or metabolic disease,

or if cardiac muscle biopsy is considered to be high risk.. After

stabilization of the child, completion of cardiac catheterization

with endomyocardial biopsy often helps to determine

hemodynamics and establish a diagnosis. Figure 2 provides a

paradigm for the stepwise approach to this diagnostic workup.

Management

Therapy for heart failure depends on the age of the patient,

specific cardiac diagnosis, time course of the symptoms (acute

versus chronic), and existence of other underlying conditions.

Practitioners should customize treatment plans based on these

factors.

Just as heart failure is a continuum with symptoms ranging

from mild to life-threatening, so is the management. Therapies

range from outpatient administration of oral medications

to listing for cardiac transplantation and implantation of

left ventricular-assist devices. The goal in managing acutely

decompensated heart failure is to restore pump function to

improve hemodynamic instability, improve symptoms and

minimize end-organ damage.

First-line therapy for mild to moderate congestive heart failure

includes diuretics such as furosemide (Lasix) or bumetanide

(Bumex) with angiotensin-converting enzyme inhibitor (ACE) or

angiotensin-recptor blocker (ARB) medications such as enalapril

and losartan and beta-blocker therapy such as carvedilol. See tabl


echocardiogram from a patient with dilated cardiomyopathy, in

comparison to a normal echocardiogram. Most patients will not

develop symptoms until their function is severely diminished,

with ejection fractions of 25 to 30 percent (with normal being

>55 percent). In the acutely decompensated state, such patients

might require inotropic or mechanical support. Many of them,however, will remain stable for a prolonged period with oral

medication treatments, before later progressing to require cardiac

transplantation.

Another increasingly important category of patients who have

heart failure are adolescents or adults with congenital heart

disease. Almost any patient who had repair or palliation of

congenital heart disease can later develop cardiac dysfunction

and HF. This might relate to poor myocardial preservation

during earlier surgeries, ventricular dysfunction from multiple

bypass runs, arrhythmias, residual defects or progressive valvulardysfunction despite repair. Patients with two specific congenital

anomalies are particularly prone to the late development of

congestive heart failure. One is single ventricle after Fontan

procedure, the other is d-transposition of the great vessels

palliated with an atrial baff le procedure. Adolescents or adults

with repaired or palliated congenital heart disease and heart

failure often benefit from a referral to a pediatric cardiologist who

is familiar with the natural history of these repaired anomalies.

These two groups of patients represent a large proportion

of adults with congenital heart disease who are referred for

consideration for cardiac transplantation.

Diagnosis

The diagnostic approach for patients with heart failure

depends on:

Age of patient

Presence or absence of congenital heart disease

Presence of systemic disorders

Severity of heart failure

Patients who have signs and symptoms of congestive heart failureshould have an evaluation by a pediatric cardiologist. Depending

on the childs presentation, the evaluation might take place on an

outpatient basis during the course of a few days. Patients also can

have an inpatient evaluation sometimes on an intensive care

unit over the course of a few hours.


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3 for a description of the mechanism of action and the physiologic

action of these medications. While there are many large, national

treatment protocols for evaluation of HF management in adults,

no such protocols exist for children or infants.

For children with more severe presentation of heart failure,

intravenous administration of inotropic drugs, such as milrinoneand dopamine, can be given acutely or chronically. The most

severe types of heart failure will require the urgent use of

extracorporeal membrane oxygenator (ECMO) or placement

of left ventricular-assist devices, and listing for cardiac

transplantation. Before 2000, the only type of circulatory support

available for infants and small children with cardiogenic shock

was ECMO. Children have a limited survival time of six to eight

weeks on ECMO before significant ECMO-related complications

usually ensue. Such difficulties include stroke, hemorrhage or

infection. Significant developments in ventricular-assist devices

(VAD) for pediatric use have occurred within the past 10 years.

The advantage of using a VAD is longer periods of use than

ECMO. The expanded use time allows a bridge to transplantation

or potentially as a bridge to recovery by giving the myocardium

a longer period of time to heal. Additionally, patients can be

extubated, awake, active, and participate in rehabilitation while

awaiting transplant.

The initial VAD use in pediatrics was limited to larger-size

children and adolescents who could receive support with devices

designed for adults, e.g., Thoratec and Heart Mate II. The initial

experience with these devices was encouraging, with 68 percent of

patients surviving to transplantation or device removal.

The newest device available for pediatric use is the Berlin Heart

EXCOR. It is commercially available in Europe and is available

on a compassionate use or FDA study use in the United States.

The Berlin Heart is available in multiple pump sizes for various

patient sizes. To date, more than 500 patients worldwide have

received support on this device, and over 200 patients within

North America.

Through 2008, the survival rates for the North Americanexperience are approaching 75 percent in the current era; the

most recent outcomes are shown in figure 3. The University of

Minnesota is one of 15 centers in the country that is an FDA

study site for the Berlin Heart. Since 2008, our program has

implanted devices in five children, and have outcomes similar to

the national data.

Once a patient develops end-stage heart failure, or are unlikely

to have recovery of myocardial function, they might need to be

listed for heart transplantation. The current indications for heart

transplantation in children include:

Need for ongoing intravenous inotropic support

Mechanical circulatory support

Complex CHD not amenable to repair or palliation

Progressive deterioration of ventricular function or functional

status despite optimal medical care

Malignant arrhythmia

Survival after cardiac arrest unresponsive to medical

treatment, catheter ablation or AICD

Progressive pulmonary hypertension that could preclude

transplantation at a later date

Growth failure secondary to severe heart failure

Unacceptably poor quality of life secondary to heart failure

Progressive deterioration in functional status and/or presence

of certain high-risk conditions following the Fontan

procedure

H E A R T F A I l U R E I N C H I l D R E N

26%Death

60.5%Transplant

8%

On Device

5.5%Weaned

Figure 3.Outcomes of Berlin

Heart Recipients


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Once it is determined that a child needs to be listed for heart

transplantation, the child is entered into the United Network

for Organ Sharing (UNOS) wait list. Each candidate awaiting

heart transplant is assigned a status code, which corresponds to

how medically urgent it is that the child receive a transplant.

The criteria for the different status levels for pediatric heart

transplant candidates are shown in table 4. Depending on the

severity of their illness, children awaiting transplantation might

be hospitalized requiring mechanical or ventilatory support,

intravenous inotropic medications, intravenous inotropic

medications at home, or oral medications at home.

A computerized match system, that UNOS operates, matches

donors and recipients based on blood type, age, size, listing status,

wait-list time and location.

The number of pediatric heart transplantations has been fairly

stable over the last 10 years, with approximately 350 to 400

transplants occurring worldwide each year. Approximately 25

percent of transplantations are on infants under the age of 1, with

the remaining number equally divided between children ages 1 to

10 years and adolescents ages 11 to 18.

The overall survival at one year after transplantation is 85

percent, with a five-year survival of 75 percent. Such survival

rates have increased in the recent era due to multiple factors

including improved surgical technique, better organ preservation,

better understanding of immunosuppression, and newer

immunosuppression medications with improved side-effect

profiles. Given these survival statistics, it is clear that heart

transplantation is not a cure and brings a host of new issues to

the forefront. However, a full discussion of the post-transplant

concerns is beyond the scope of this article. Our goal is to allow

a child to keep their own heart as long as possible. If a child has

recovery of function and practitioners are able to maintain the

child on oral medications with a good quality of life, they might

be de-listed for transplant and followed closely.

Conclusions

Heart failure in children is a complex disease process that haswidespread effects throughout the body. The clinical presentation

of heart failure in infants and children can be easily mistaken for

primary respiratory illness or other systemic disease processes,

making the diagnosis can be difficult.

Discovering the exact etiology of HF in children can be a difficult

challenge. In the acute setting, therapy is directed at restoring

hemodynamic stability and minimizing end organ damage. In

the patient with chronic heart failure, therapies are directed at

improving long-term outcomes by minimizing inflammatory an

fibrotic changes to the myocardium and systemic and pulmonar

vascular systems. Some patients might have progression of their

heart failure despite optimal medical therapy. New ventricular-

assist devices in development for pediatric patients offer another

therapeutic option with the hopes of decreasing wait-list mortali

for children who are awaiting heart transplantation. Heart

transplantation remains a viable option for patients with end-sta

heart failure, with improving survival outcomes in the most rece

decade. However, wait-list mortality due to limited donor organ

availability and long-term morbidity and mortality associated wi

transplantation continue to be an issue.


References

1. Auslender, M. Progress in Pediatric Cardiology2000; 11:175-184. Pathophysiology of pediatric heart failure.

2. Wilinson, JD., et al. Progress in Pediatric Cardiology2008;

25: 31-36. The Pediatric Cardiomyopathy Registry:

1995 2007.

3. Auslender, M. and Artman, M. Progress in Pediatric

Cardiology2000; 11: 231-241. Overview of the

management of pediatric heart failure.

4. Jeffries, JL. Progress in Pediatric Cardiology2007; 23: 61-66

Novel medical therapies for pediatric heart failure.

5. Lipschultz, SE. Progress in Pediatric Cardiology2000; 12:

1-28.Ventricular dysfunction clinical research in infants,

children and adolescents.

6. Gandhi, SK. Progress in Pediatric Cardiology 2009; 26:

11-19.Ventricular assist devices in children.

7. Rosenthal D. et al.J Heart Lung Transplant2004; 23:

1313-33. International society for heart and lung

transplantation: Practice guidelines for management of

heart failure in children.8. Swedberg K, et al. Circulation 1990; 82: 1730-6.

Hormones regulating cardiovascular function in

patients with severe congestive heart failure and their

relation to mortality.

9. Cohn JN. Circulation 2002; 106: 2417-8. Sympathetic

nervous system in heart failure.

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