The Sick Neonate With Cardiac Disease - …...The Sick Neonate With Cardiac Disease Jennifer F....

Abstract:The approach to the infant with acardiac emergency begins withidentification of the unstable orcritically ill child and proceedsrapidly into stabilization and provi-sion of immediate therapies. Sup-port of oxygenation, ventilation,and circulation will precede identi-fication of specific cardiac lesions.The emergency clinician can useclinical findings, chest x-ray, andelectrocardiographic information toplan emergent intervention. Infantsin the first days of life who presentwith circulatory collapse secondaryto obstruction of pulmonary orsystemic blood flow (ductus de-pendent) conditions can be stabi-lized with prostaglandin E infusion.The more common presentation ofcardiac disease in the first monthof life is congestive heart failure.Infants with congestive heart fail-ure require respiratory support,careful fluid management, andinotropic support.

Keywords:congenital heart disease;prostaglandin

Johns Hopkins University School ofMedicine, Baltimore, MD.Reprint requests and correspondence:Jennifer Anders, MD, Johns HopkinsChildren's Center, Division of PediatricEmergency Medicine, CMSC-144, 600 N.Wolfe St, Baltimore, MD [email protected]

1522-8401/$ - see front matter© 2011 Elsevier Inc. All rights reserved.

THE SICK NE

The Sick NeonateWith Cardiac

Disease

ONATE WITH CARDIAC DISEASE /

Jennifer F. Anders, MD,Karen A. Schneider, RSM, MD, MPH

he approach to the infant with a cardiac emergencybegins with recognition of the unstable state and
Tproceeds rapidly to stabilization and provision ofimmediate therapies. Once a child has been identified
as needing immediate care, there are few specific indicators thatthe underlying cause is cardiac. Neonates with critical cardiaclesions are often initially indistinguishable from neonates withoverwhelming bacterial or viral infections or a metabolic orendocrine crisis. The clinician must recognize early shock in aninfant with attention to respiratory effort, mental status, and colorchanges. Initial resuscitative measures will focus on airwaysupport, oxygenation, and ventilator assistance and circulatorysupport (establish venous access and cardiac monitoring). Asinterventions proceed, elements that may point to an underlyingcardiac cause of illness include hypoxia, which does not respondto supplemental oxygen, pulse, oxygen saturation or bloodpressure differential between upper and lower limbs, cardiacmonitor/electrocardiogram (ECG) abnormalities, chest x-rayfindings, and hepatomegaly.

The primary airway concern in neonates with cardiac disease isdepressed mental status that may allow upper airway obstruction.However, congenital cardiac lesions may occur in concert withother congenital syndromes, which include airway anomalies (eg,choanal atresia, Pierre Robin syndrome), or as a secondarycomplication after neonatal intensive care. In addition, the sickneonate is at a high risk for apnea and upper airway obstructionwhen stressed and must be carefully monitored for interventionand provision of airway support when needed. Before proceedingwith elective endotracheal intubation, the physician mustcarefully assess the infant for a potential difficult airway and beprepared with an alternate airway management plan in caseendotracheal intubation is not successful.

ANDERS AND SCHNEIDER • VOL. 12, NO. 4 301

mailto:jander74@jhmi.�edu

302 VOL. 12, NO. 4 • THE SICK NEONATE WITH CARDIAC DISEASE / ANDERS AND SCHNEIDER

Infant respiratory reserves are limited, andneonates with cardiac lesions frequently showsigns of respiratory distress. Both cyanotic andnoncyanotic heart disease will include respiratorydistress. Oxygen will likely be initiated immediatelyupon arrival of the distressed neonate. Childrenwhose hypoxia resolves after administration ofsupplemental oxygen should continue to receiveoxygen by face mask or nasal cannula. Hypoxia thatfails to resolve with administration of high-flowsupplemental oxygen likely represents cyanoticcongenital heart disease. Hyperoxygenation of in-fants with mixing lesions can create complications.For most cyanotic congenital heart disease lesions, areasonable goal for oxygen saturation is 75% to 85%.Rapid onset of intense cyanosis, particularly in thefirst 2 weeks of life, strongly suggests the presence ofductal dependent cyanotic congenital heart disease.Supplemental oxygen should be used sparingly inthese infants, as high oxygen levels will speedclosure of the ductus arteriosus, which may precip-itate rapid decline.

Venous access should be obtained rapidly in anysick neonate. For a child with symptoms of shock,including decreased level of consciousness oragitation, diminished pulses, or prolonged capillaryrefill, bolus isotonic fluids should be provided byintravenous or intraosseus route. An initial bolus ofisotonic fluids at 10 mL/kg will support circulationwith minimal risk of worsening cardiac function ina neonate.1

As basic resuscitation measures proceed, theclinician will simultaneously turn to diagnosticconsiderations. History taking should include thematernal medical history and prenatal exposures.Table 1 lists prenatal risk factors for congenitalheart disease. The differential diagnosis of neonatal

TABLE 1. Prenatal (maternal) exposures as riskfactors for congenital cardiac disease.

Alcohol ASD, VSDLupus Complete heart blockValproic acid Coarctation of aorta, hypoplastic left ventricle,

AS, pulmonary atresiaRetonic acid Conotruncal anomaliesDiabetes Hypertrophic cardiomyopathy, VSD,

conotruncal anomaliesPhenylketonuria VSD, ASD, PDA, coarctation of aortaRubella PDA, peripheral pulmonic stenosis

Abbreviations: AS, aortic stenosis; ASD, atrial septaldefect; PDA, patent ductus arteriosis; VSD, ventricularseptal defect.

cardiac emergencies requires an understanding offetal and transitional circulation.

FETAL AND TRANSITIONAL CIRCULATIONThe 3 unique structures in fetal circulation are

the ductus venosus, foramen ovale, and the ductusarteriosus. The umbilical vein transports oxygenatedblood from the placenta through the ductus venosusto the inferior vena cava where it joins thedeoxygenated blood from the lower body. Thismixed blood enters the right atrium where it isdirected through the foramen ovale to the leftatrium, thus bypassing the right ventricle (RV) andthe pulmonary circulation. The blood traverses fromthe left atrium to left ventricle (LV) to the aorta.Meanwhile, deoxygenated blood from the upperbody is carried by the superior vena cava into theright atrium and is directed through the tricuspidvalve into the RV. With the next contraction, thisblood is pushed into the pulmonary artery, but thepulmonary system is vasoconstricted, so only about10% of blood enters the pulmonary circulation. Theremainder of the blood takes the path of leastresistance into the ductus arteriosus, a conduitinto the descending aorta and the lower part of thebody eventually landing in 1 of the 2 umbilicalarteries and returning to the placenta.

With the infant's first breath, an increase in PaO2

results in a rapid decrease in pulmonary vascularresistance. As a result, blood preferentially flowsfrom the right side of the heart to the low-resistance pulmonary circulation. Cessation oflow-resistance placenta circulation immediatelyraises the systemic vascular resistance. Withsystemic vascular resistance higher than pulmo-nary resistance, the ductus arteriosus flow re-verses, with blood now flowing from the aorta tothe pulmonary artery. Over hours to days, theductus arteriosus constricts and closes. The highflow and, thus, high pressure into the left atriumenables the foramen ovale to close. The RV thins aspulmonary resistance falls, whereas the left ventri-cle wall begins to thicken once exposed to highersystemic vascular resistance.

IDENTIFICATION OFCARDIAC EMERGENCIES

Cardiac emergencies in infants can be categorizedas structural or nonstructural. Structural defects canbe further defined as either volume overload orobstructive (pressure overload) states. Nonstructuralemergencies include arrhythmias (bradycardia andtachycardia) and disorders of myocardial function.

THE SICK NEONATE WITH CARDIAC DISEASE / ANDERS AND SCHNEIDER • VOL. 12, NO. 4 303

Several reliable online resources are available withdiagrams and additional description of the fullspectrum of congenital heart disease lesions. Anexample is the site maintained by the Johns HopkinsHelen Taussig Heart Center at www.pted.com.2

STRUCTURAL DEFECTS: VOLUMEOVERLOAD CONDITIONS

When a left to right shunt exists, fully oxygenatedblood from the left side of the heart circulates backto the right side of the heart, and forms a repeatcircuit, through the pulmonary circulation. Exam-ples of left to right shunt conditions include atrialseptal defect (ASD), ventricular septal defect (VSD),atrioventricular (AV) canal defects, partial anoma-lous pulmonary venous return, and patent ductusarteriosus (PDA). The volume of blood passingthrough the shunt and, thus, the severity of thecondition depends on differences between pulmo-nary and systemic vascular resistance. As neonatalcirculation transitions, these pressures are labile,and thus, rapid changes in condition can occur. Thedecline of pulmonary vascular resistance in neo-nates occurs over hours to weeks. If a septal defect ispresent, the left to right shunt will be minimal soonafter birth when the pulmonary vascular resistanceis high, but as pulmonary vascular resistance falls,the shunt volume will increase, and the infant willdevelop right side of the heart overload andsymptoms of congestive heart failure. Anotherexample of volume overload is regurgitant valves.This is most commonly seen in patients with AVcanal defects. Ebstein anomaly is an isolatedregurgitation of the tricuspid valve.

The principal negative consequence of volumeoverload in neonates is poor pulmonary function.Increased vascular volume decreases pulmonarycompliance, increasing work of breathing requiredfor effective ventilation. At the same time, fluidleaks from the vasculature into the alveolar spaces(pulmonary edema) and impedes oxygenation. Theclinical appearance of an infant with a volumeoverload state is hypoxia and respiratory distress;frequent signs include tachypnea, retractions, andwheezing. Infants will usually have decreasedtolerance for feeding and often fail to keep pacewith growth percentiles. In addition, volume over-load and high right atrial pressures rapidly lead tohepatic congestion and hepatomegaly.

Ventricular Septal DefectVentricular septal defect is, by far, the most

common congenital cardiac malformation, repre-

senting about 25% of congenital heart disease.3 Theamount of shunting depends on the size of thedefect and pulmonary and systemic vascularresistance. Defects less than 0.5 cm in diameterare termed restrictive because the small commu-nication does not allow for significant left to rightshunt. Defects greater than 1 cm in diameter aretermed nonrestrictive and are associated with leftto right shunting. Severity depends on the size ofthe defect and the infant's pulmonary and systemicvascular resistance. In addition to the clinicalfeatures of volume overload, neonates with VSDsusually have an audible murmur. In very largedefects, the flow across the defect may lack theturbulence necessary to generate an audible mur-mur. When present, a VSD murmur is best heardalong the lower left sternal border and is describedas harsh and holosystolic. Chest x-ray will showcardiomegaly, with prominence of both ventricles,left atrium, and pulmonary artery as well aspulmonary edema with increased pulmonary vas-cular markings. Electrocardiographic findings arenonspecific, showing biventricular hypertrophy.

Atrial Septal DefectAtrial septal defects are described in 3 types:

secundum, primum, or sinus venosus. A patentforamen ovale is not considered an ASD becausethe flap structure of the foramen does not usuallyallow shunting. As with VSDs, the degree ofshunting depends on the size of the defect andthe pulmonary and systemic resistance. Volumeoverload conditions should not become clinicallyapparent in the neonatal period, but prolongedstress on the RV can lead to eventual right sidedheart failure later in life. In general, ASD shouldnot cause significant illness in an infant, butpresence of an ASD in conjunction with certainright side of the heart obstructive lesions (tricus-pid atresia, transposition of the great arteries[TGA]) can allow enough shunting for the infantto survive past the newborn period withoutdetection. Clinical signs of congestive heart failureare less likely than with VSD, and emergentpresentation in the neonatal period is unlikely. Asystolic murmur may be heard at the left uppersternal border, and the second heart sound (S2)may be widely split and fixed. Chest radiographfindings are not expected, and ECG findings arenot apparent in the neonatal period.

Partial Anomalous Pulmonary Venous ReturnPartial anomalous pulmonary venous return de-

scribes a portion of the pulmonary venous system

http://www.pted.com


that does not connect to the left atrium but insteadjoins the systemic venous return into the rightatrium. This circulatory loop creates a left to rightshunt and overcirculation of the right side of theheart and pulmonary system. The degree of shunt-ing depends on the proportion of pulmonary veinsinvolved. Clinical signs are those common to volumeoverload conditions, including hypoxia, respiratorydistress, and hepatomegaly. Nomurmur is associated.Chest radiograph may show lack of pulmonaryvenous markings. If the anomalous vein enters theinferior vena cava, a crescent shadow may be visiblealong the right border of the heart. This finding isknown as Scimitar syndrome. Electrocardiographicfindings are nonspecific during the neonatal period.

Total Anomalous Pulmonary Venous ReturnTotal anomalous pulmonary venous return is a

more severe version where all pulmonary veinsreturn to the systemic venous return system insteadof emptying to the left atrium. This entry may bedirectly into the right atrium, into the superiorvena cava, the inferior vena cava, or the veinsmay even descend below the diaphragm andenter the portal vein. The result is a total mixinglesion of oxygenated and deoxygenated blood and alack of flow into the systemic circulation. An ASDmust also be present for the neonate to survive.Infants with ASD will present with volume overloadstates. Chest x-ray findings include cardiomegalyand increased pulmonary vascular markings. TheLV is poorly developed, and an ECG will show rightventricular hypertrophy.

Endocardial Cushion DefectEndocardial cushion defects refer to a range of

conditions (including complete AV canal, AV septaldefects) in which one or more portions of the AVseptum fails to form and/or the AV valves formabnormally. Presentation of these conditions rangefrom very mild (ASD) to severe forms (complete AVcanal). Complete AV canal is frequently associatedwith trisomy 21. Valve defects with regurgitation addto volume overload. Clinical signs are those commonto volume overload conditions, including hypoxia,respiratory distress, and hepatomegaly. Auscultoryfindings with this condition are variable, dependingon the exact defect, but frequently include a widefixed split of S2 and pulmonary ejection murmur.Infants with mitral insufficiency will have an apicalholosystolic murmur that radiates to the axilla.Chest x-ray will show varying degrees of cardiome-galy. Electrocardiographic findings (see Figure 2)may include superior oriented QRS axis, RV

hypertrophy, right bundle-branch block, left ven-tricular hypertrophy, or prolonged PR interval.

Truncus ArteriosusA truncus arteriosus refers to an anomaly where

the aorta and pulmonary artery arise as a singlevessel directly above a large VSD, allowing totalmixing of deoxygenated and oxygenated blood. Aspulmonary vascular resistance falls, blood willpreferentially flow into the pulmonary system,thus creating left to right shunting and volumeoverload. Truncus arteriosus is usually clinicallyapparent at the time of birth with cyanosis, butpresentation can be delayed if pulmonary vascularresistance is adequately high. Chest x-ray will showcardiomegaly. Electrocardiogram will show biven-tricular hypertrophy and may lack the right-axisdeviation expected in a neonate.

Patent Ductus ArteriosusThe normal ductus arteriosus differs from the

aorta and pulmonary artery in that its middle layercontains circularly arranged smooth muscle. If theductus arteriosus fails to close in a full-term infant inthe first weeks of life, there is likely a deficiency ofboth the mucoid endothelial layer and muscularmedia of the vessel, and this vessel will never closeon its own.

The extent of left to right shunt depends on theratio of pulmonary to systemic pressures and thesize of the PDA. A large PDA can lead to congestiveheart failure and failure to thrive. Clinical charac-teristics of PDA can be striking. Infants with a largePDA may have a wide pulse pressure and boundingarterial pulses due to runoff of blood into thepulmonary artery during diastole. A thrill may befelt along the second left intercostal space withradiation to the left clavicle, down the left sternalborder, or to the apex. The defining characteristicof a PDA is that it has been described as amachinery-like continuous murmur that beginssoon after the first heart sound, crescendos throughsystole and wanes through diastole. Chest x-raymay show a large pulmonary artery with increasedpulmonary vascular markings. Electrocardiographicfindings are nonspecific. If the PDA shunt is large,the ECG may have signs of left ventricular orbiventricular hypertrophy.

Conotruncal Anomalies: Double-Outlet RV,Double-Inlet Left Ventricle, and Tetralogy of Fallot

The conotruncal anomalies include a variety ofcomplex congenital heart disease. Numerous


variations of these conditions exist, and a detaileddescription is not necessary for emergency care.These conditions are marked by mixing ofoxygenated and deoxygenated blood, usually withcyanosis apparent from birth, and may haveincreased or decreased pulmonary blood flow.Infants with increased pulmonary blood flow willpresent with signs of volume overload and conges-tive heart failure. Infants with decreased pulmo-nary blood flow will present with cyanosis.Tetralogy of Fallot is the most common of theseconditions and frequently presents in the emer-gency department. Tetralogy of Fallot consists of 4specific anomalies: (1) pulmonary stenosis, (2)VSD, (3) aorta overriding both the right and leftventricle outflow tracts, and (4) right ventricularhypertrophy. The combination of pulmonary ste-nosis and VSD creates a right to left shunt andcyanosis. Wide variability is seen in the degree ofpulmonary stenosis. Infants with critical pulmonicstenosis are dependent on the PDA for blood flowto the lungs and will present with profoundcyanosis when the ductus closes. Infants withmild stenosis of the pulmonary valve may beacyanotic (“pink Tet”) and present with intermit-tent cyanosis or signs of heart failure. Clinicalfeatures common to neonates with tetralogy ofFallot include a loud, harsh systolic murmur at thelower left sternal border. Approximately 50% havean associated thrill. Chest x-ray findings includecardiomegaly and right ventricular hypertrophywith decreased vascular markings (Figure 2). Thisappearance is sometimes compared with a boot ora wooden shoe. An ECG should show right-axisdeviation and right ventricular hypertrophy.

Infants with tetralogy of Fallot frequently pre-sent with cyanotic episodes or “Tet spells.” Theseepisodes commonly occur in early morning afterwaking and may be provoked by exercise orvigorous crying. The infant becomes fussy, cya-notic, and tachypneic and may proceed tosyncope. Spells represent a temporary increasein right to left shunting secondary to decreasedpulmonary blood flow. On cardiac auscultation, apreviously noted murmur may be less prominentor absent because of the reduction of pulmonaryblood flow. Therapy for these spells is directed atcalming the infant and increasing pulmonary bloodflow through a variety of methods: decreasingpulmonary vascular resistance (oxygen and mor-phine are potent pulmonary vasodilators) andincreasing systemic venous return (knees-to-chestpositioning or abdominal compression).4,5 In aprolonged spell, the infant may develop metabolicacidosis requiring treatment with sodium bicar-

bonate. β-Adrenergic blockade has been shown tobe helpful especially in infants with severe cryingand tachycardia. Drugs that increase systemicvascular resistance such as phenylephrine willincrease right ventricular outflow, decrease rightto left shunt, and thus, improve symptoms.

Ebstein AnomalyEbstein anomaly is a rare defect of the tricuspid

valve where the tricuspid valve is displaced down-ward into the RV. The tricuspid valve is regurgitant,the right atrium is dilated and hypertrophied, andthe RV is hypoplastic and dysfunctional. In addition,Wolff-Parkinson-White (WPW) syndrome is com-monly associated with this anomaly. Neonates maypresent with cyanosis and right to left shunting.Clinical features of Ebstein anomaly include hepa-tomegaly and features of right sided heart failure.Massive dilation of the right atrium can causerespiratory distress by bronchial obstruction. Clas-sic description of cardiac auscultation includesfindings of split first heart sound and S2 as well asthe presence of third heart sound and fourth heartsound. The tricuspid regurgitation murmur may beheard at the lower left sternal border as a softsystolic murmur. Extreme cardiomegaly can beseen on chest x-ray of neonates with Ebsteinanomaly. Possible ECG findings include both shortPR interval in 20% and long PR interval in 40%; rightatrial hypertrophy and right bundle-branch blockshould be present. Neonates who present withdecompensated Ebstein anomaly have an extremelyhigh risk of neonatal death.6,7 In severely cyanoticinfants, this is a ductus-dependent lesion. Immedi-ate therapy with prostaglandin infusion, vasopressorinfusion, and correction of metabolic acidosis willlikely be necessary to maintain the infant beforesurgical intervention.

STRUCTURAL HEART DEFECTS:OBSTRUCTIVE CONDITIONS

Obstructive lesions present in 2 main ways. Themore dramatic form is of critical interest to theemergency physician and will present in the earlyneonatal period with cardiovascular collapse be-cause blood is unable to flow into the pulmonary orsystemic circulation. These lesions may be presentfrom the moment of birth or may not be clinicallyapparent until the ductus arteriosus closes. Incom-plete forms of obstructive lesions will createpressure overload states that may not be apparentin the first weeks of life but will eventually lead to

TABLE 2. Ductus dependent cardiac lesions.

Tetralogy of Fallot (with critical pulmonary stenosis)Coarctation of the aortaTricuspid atresiaHypoplastic left heart syndromePulmonary atresiaPulmonary stenosis (critical)


ventricular hypertrophy or dysfunction. Table 2lists the ductus dependent cardiac lesions.

Pulmonary Valve StenosisPulmonary outflow tract obstruction (critical

pulmonary stenosis and pulmonary atresia) pre-sents soon after birth with cyanosis and right sidedheart failure. Pulmonary blood flow is suppliedexclusively by retrograde flow through the PDAfrom the aorta to the pulmonary artery. Clinicalpresentation may initially be cyanotic because ofright to left shunting of deoxygenated bloodthrough the foramen ovale or signs of severeheart failure with hepatomegaly and peripheraledema. If they are not previously identified bythese signs, infants will present with cardiovascularcollapse when the ductus arteriosus closes. Chestx-ray findings are nonspecific, with cardiomegalyand decreased pulmonary vascular markings.Electrocardiogram shows LV hypertrophy becauseof a hypoplastic right ventricle and a relativelylarge left ventricle. Critical pulmonary stenosisrequires emergency treatment with prostaglandinE1 infusion.

Coarctation of the AortaPresentation of coarctation is highly variable

based on degree of narrowing. In the critical form,coarctation presents at time of closure of the ductusarteriosus. Less severe forms can present months toyears later with ventricular hypertrophy andsystemic hypertension. Neonates with critical co-arctation appear pale with circulatory collapse andsevere metabolic acidosis. Coarctation usuallyoccurs in the descending aorta after the origin ofthe right and left subclavian arteries. Clinicalfindings that support the diagnosis of coarctationinclude diminished or absent femoral pulses,differential pulse oximetry readings on preductal(upper body) and postductal (lower body) sites orlower body cyanosis, and blood pressure differentialbetween upper and lower extremities. A short

systolic murmur may be heard at third or fourthintercostal space along the left sternal border.Chest x-ray may show cardiomegaly. Electrocar-diogram is usually normal in the first weeks of lifebut, later, may show RV hypertrophy or rightbundle-branch block.

Hypoplastic Left Heart SyndromeHypoplastic left heart syndrome (HLHS) includes

a constellation of anomalies including mitral andaortic valve atresia and hypoplasia of the aortic root.Systemic blood flow is supplied exclusively via thePDA. Newborns can have surprisingly few symptomsat birth then present suddenly with cardiovascularcollapse as the ductus closes. Chest x-ray findingsare nonspecific. Electrocardiographic findingsof HLHS include peaked P waves and RV hypertro-phy. Without surgical intervention, HLHS is uni-formly fatal in the neonatal period. Emergentcare is directed at supporting flow through theductus arteriosus with prostaglandin infusion andsupportive critical care to allow the infant to surviveto surgery.

Transposition of the Great VesselsIn transposition of the great vessels, alternatively

known as TGAs, the origin of the 2 great vessels isswitched. The aorta arises from the RV, thuscarrying deoxygenated blood back to the body.The pulmonary artery arises from the LV andcarries oxygenated blood back to the lungs. Trans-position of the great arteries with an intact atrialseptum will present at birth with profound cyanosis.If an ASD or patent foramen ovale is present andallows adequate mixing, it is possible that a childcould be only mildly symptomatic at birth, but whenthe ductus arteriosus begins to close, the child willbecome more cyanotic and rapidly collapse.

Tricuspid AtresiaTricuspid atresia blocks outflow from the right

atrium into the RV. Deoxygenated blood must shuntright to left through the foramen ovale. Flow to thepulmonary system is limited to left to right shuntthrough the ductus arteriosus. Cyanosis is usuallyobvious at birth, but some infants will have intermit-tent hypoxia only. Neonates will present withcyanosis as the ductus closes. Chest x-ray findingsare subtle, without cardiomegaly, but pulmonaryvascular markings are usually decreased. Hypoplasiaof the RV is reflected in the ECG with superior QRSaxis, right atrial hypertrophy and left atrial hyper-trophy, and LV hypertrophy.


NONSTRUCTURAL CARDIAC EMERGENCIESIN NEONATES

ArrhythmiaBradycardia in newborns occurs most frequently

secondary to other illness such as hypoxia, hypo-glycemia, hypothermia, and sepsis. Congenitalcomplete AV block is most often seen in infantsborn to mothers with systemic lupus erythematosusor other collagen vascular disease. Electrocardio-gram should reveal a junctional escape rhythm andrate of 60 to 80. If the infant is symptomatic becauseof bradycardia, congenital complete AV block istreated with pacing. Tachyarrhythmias such assupraventricular tachycardia can present in theearly neonatal period, and are often associated withstructural congenital heart disease. Arrhythmias arediscussed elsewhere in this issue.

Myocardial DysfunctionA wide variety of conditions can lead to myocar-

dial dysfunction in neonates. Signs of congestiveheart failure and poor contractility can be seen ininfants with overwhelming sepsis or hypoxia sec-ondary to respiratory disorders. More esotericpossibilities include inborn errors of metabolism,viral myocarditis, and congenital cardiomyopathy.

Anomalous Left Coronary ArteryThe normal origin of the coronary arteries is from

the coronary ostia at the base of the aorta. In this rare

Figure 1. Chest radiograph of infant with tetralogy of Fallot. Boo

condition, the left coronary artery arises instead fromthe pulmonary artery. The myocardium is thereforesupplied with deoxygenated blood at relatively lowerpulmonary vascular pressures. As pulmonary resis-tance declines in the first weeks of life, coronaryperfusion slows, and myocardial ischemia and infarc-tion occur in early infancy. This condition has beensuggested as a possible etiology of colic and as apotential mimic of bronchiolitis.8,9 Infants typicallypresent with signs of dilated cardiomyopathy andcongestive heart failure: feeding intolerance, respira-tory distress with wheezing, and hepatomegaly. Chestx-ray will reveal cardiomegaly and pulmonary edemain late stages. Before infarction and failure, ECG willshow classic ischemic changes such as ST elevationsand T-wave inversions in the precordial leads. LateECG findings are consistent with old infarction,particularly deep and wide Q waves in the precordialleads. The diagnosis is made by echocardiogram.Treatment is supportive, pending urgent surgicalreimplantation of the coronary arteries.10

DIAGNOSTIC TESTING AND THERAPY

Interpretation of Chest RadiographA chest radiograph should be obtained in the infant

with suspected cardiac disease. A short list of simpleassessments by the emergency physician can narrowthe differential diagnosis: measurement of heart size,assessment of pulmonary vascular markings, andpresence of a right-sided aortic arch. Most classicdescriptions of common lesions use combinations of

t shape of the heart results from right ventricular hypertrophy.

TABLE 3. Stepwise approach to chest x-rayinterpretation in infants with suspected

cardiac disease.

Is there obviouscardiomegaly?

If yes, increases likelihood ofcongenital heart disease orcardiac failure. Predominantlyvolume overload states. Massivecardiomegaly suggests Ebsteinanomaly or cardiomyopathy.

Is there evidence of increasedpulmonary vascular markings? Increased pulmonary vascular

markings suggests a pulmonaryoverflow state, with inadequatesystemic flow. Conversely, lack ofexpected pulmonary vascularmarkings suggests obstruction ofpulmonary circulation.

Is there a right-sided aorticarch? Tetralogy of Fallot, truncus

arteriousus, tricuspid atresiaIs there normal abdominalsitus? Situs inversus suggests TGAs.


these assessments. For example, the appearance oftetralogyof Fallot onchest x-ray (Figure1) ismoderatecardiomegalyandlackofprominentpulmonaryvessels(“woodenshoe”),possiblywitharight-sidedaorticarch(“boot shape”). Table 3 outlines a stepwise approachto the interpretation of an infant's chest x-ray.

Interpretation of Infant ECGPrinciples of electrocardiography are the same

regardless of age. The sinoatrial node located in theright atrium is the pacemaker for the heart. Thesinoatrial node sends out an electric impulse thatsimultaneously depolarizes the right and left atria,producing a P wave. As the electrical impulse passesthrough the AV node, the conduction slows, produc-ing the PR interval. The electrical impulse thentravels through the right and left branches of theBundle of His to depolarize the ventricular muscle,thus producing the QRS complex. The T wave iscreated by the repolarization of the ventricles.

The normal neonatal heart rate ranges between110 and 150 but varies greatly and increases withcrying, fever, or activity. From birth through the firstmonth of life, the RV muscle is thicker than the leftventricle; thus, the ECG tracing reveals right-axisdeviation and right ventricular hypertrophy. Thenormal infant QRS axis is right and anterior (+135 to+180), whereas R-wave amplitude is higher in theright precordial leads (V1 and V2) and the S-wave

amplitude peaks in the left precordial leads (V5 andV6). T waves are typically inverted in all precordialleads in infants (Figure 2). In infants older than 3days, an upright T wave in V1 is highly unusual andsuggests right ventricular hypertrophy. Presence of asuperior axis (−1 to −180) suggests the presence of anAV canal or tricuspid atresia (Figure 3). Table 4 listsadditional ECG abnormalities that can be seen inneonatal cardiac disease.

Laboratory FindingsA limited number of laboratory studies may be

specifically useful in the evaluation and treatmentfor infants with congenital heart disease. It is likelythat most sick neonates will undergo a standardcomprehensive laboratory evaluation to eliminateother diagnostic considerations such as infectiousand metabolic diseases. From common screeninglaboratory testing, renal and hepatic functions arethe most likely to be abnormal in poorly perfusedneonates. Arterial blood gas measurement mayprovide specific diagnostic information and shouldbe pursued in neonates with suspected cardiacdisease. The hyperoxia test measures PaO2 in theright radial artery while the neonate is receiving100% oxygen. Demonstration of arterial oxygencontent less than 150 mm Hg suggests a cardiacmixing lesion. In addition, measurement of arterialpH may prompt specific therapy for metabolicacidosis. Lactate levels may be useful to evaluatethe impact of the low perfusion state and guidecritical care therapies. Troponin levels have beenshown to correlate with myocardial injury and inneonates with severity of volume overload with PDAbut are not a specific marker and are also elevated inneonatal respiratory distress syndromes.11-13

EchocardiographyFor an infant with actual or impending circula-

tory collapse, an echocardiogram should beobtained as urgently as possible to define thelesion and guide surgical or medical therapy. Theemergency provider proficient with the focusedassessment with sonography in trauma (FAST)examination may be comfortable using bedsideultrasound to obtain a subxyphoid view of theheart, but it cannot substitute for echocardiogramby an experienced examiner.

Therapeutic InterventionsThe crux of advanced therapeutic management of

the infant with cardiogenic shock is balance ofpulmonary and systemic blood flow. For infants with

Figure 2. Infant ECG with right ventricular hypertrophy. Signs of right ventricular hypertrophy include larger than normal amplitudes of R and inverted T waves in right precordial leads.

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Figure 3. Electrocardiogram of infant with complete AV canal defect. Note the superior axis deviation. QRS is downgoing in aVF, indicating electrical axis “away” from the lower body.

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TABLE 4. Electrocardiographic interpretation for infants with suspected cardiac disease.

Assess rateRate b80 beat/min Bradycardia Congenital AV block, hypoxia, hypothermiaRate N160 beat/min Tachycardia Sinus tachycardia, ventricular tachycardia,

Supraventricular tachycardiaAxis determinationQRS upright in lead I and downward in

aVFRight-axis deviation Expected in healthy infants

QRS upright in aVF Superior axis Endocardial cushion defect or tricuspid atresia

Assess PR intervalThe PR interval is most easily measuredin lead II

PR interval long Ebstein anomaly, hypoxia, digitalis toxicity, hyperkalemiaPR interval short Wolff-Parkinson-White, glycogen storage disease

Assess QRS Q waves present in V1 notin V6

Severe right ventricular hypertrophy, transposition ofgreat vessels, single ventricle, mirror image dextrocardia

Deep Q waves Ventricular hypertrophy (left, right or bi-ventricular hypertrophy),anomalous left coronary artery, idiopathic hypertrophicsubaortic stenosis

QRS amplitude large Ventricular hypertrophyRight bundle-branch block Endocardial cushion defect, coarctation of the aorta

Assess T wavesThe amplitude of the T wave isbest measured in left precordialleads (V5 and V6)In V5 (b1 y), 11 mm; in V6(b1 year), 7 mm

Tall or peaked T waves Hyperkalemia, left ventricular hypertrophyLow or flat T waves Normal newborn, hypoglycemia, myocardial ischemia


ductal dependent lesions, this includes supportingpatency of the ductus arteriosus.

ProstaglandinProstaglandin E1 (PGE1) infusion should be con-

sidered immediatelywhen infants presentwith severehypoxia or shock in the first 1 to 2 weeks of life. A listof ductus-dependent lesions that may benefit fromPGE1 infusion is found in Table 2. However, thedecision to initiate PGE1 infusion should be made onclinical grounds and not wait for definitive diagnosis.ProstaglandinE1 halts closure of the ductus arteriosusand can result in rapid clinical stabilization of theinfant with a ductus-dependent lesion. Initial dosingincludes a bolus of 0.1 mg/kg followed by continuousinfusion at a rate of 0.05 to 0.1 μg/kg per minute.Prostaglandin infusion does not require centralvenous access but does require a dedicated intrave-nous site to ensure continuous infusion.

Prostaglandin infusion has several frequent andsevere adverse effects.14 Apnea occurs in 12% ofneonates receiving PGE1, and for that reason,elective intubation should be considered beforetransport of an infant on prostaglandin infusion.

Other potentially life-threatening adverse effects ofprostaglandin infusion include bradycardia, hypo-tension, and seizures. Fever occurs in about 10% andmay complicate clinical diagnosis by raising suspi-cion of sepsis. Flushing, or cutaneous vasodilatation,also occurs in about 10%.

Ionotropes and VasopressorsSeveral inotropic agents may be useful for emer-

gent stabilizationof the infantwith cardiogenic shock.Choice of agent shouldbebased on the relative balanceof pulmonary and systemic blood flow. Ideally, theratio of pulmonary flow to systemic flow should be 1:1.Pulmonary and systemic blood flow exists as a zero-sum equation; when the pulmonary circuit is over-circulated, the systemic circulation is hypoperfusedand vice versa. In addition to any effects on cardiaccontractility or heart rate, available inotropes act toincrease or decrease systemic vascular resistance.When blood is shunted toward the pulmonary circu-lation, the goal of therapy is to increase systemiccirculation, and thus, the preferred inotropic agentsare those that will reduce systemic vascular resistancesuch as milrinone and dobutamine. When blood is


shunted away from thepulmonary circulation, the goalof therapy is to decrease systemic circulation, andthus the preferred inotropes are those that will raisesystemic vascular resistance such as high-dosedopamine and epinephrine. Inhaled nitrous oxideand sildenafil are 2 pharmacologic agents that acton pulmonary vascular resistance, although they areunlikely to be initiated in the emergency depart-ment setting.

Sodium BicarbonateUse of sodium bicarbonate to treat metabolic

acidosis is fraught with controversy. Extreme acido-sis places further stress on the heart and brain.However, the weight of current evidence suggeststhat administration of bicarbonate does more harmthan good in neonates with metabolic acidosissecondary to hypoperfusion. Use of bicarbonatehas been shown to increase troponin levels inchildren with acute renal failure and to depressmyocardial function in animal models.15,16 Inaddition, bicarbonate does not cross the bloodbrain barrier, whereas carbon dioxide crosses freely.Therefore, administration of bicarbonate may para-doxically worsen cerebral acidosis. There is consen-sus that the initial priority must be on correction ofrespiratory acidosis and support of circulation.17

SUMMARYEmergent care of the neonate with congenital

heart disease includes recognition of an unstablecondition and standard resuscitative measures tostabilize. Airway management with intubation andventilatory support should be strongly consideredfor critically ill infants. For infants with suspectedductal-dependent lesions, prostaglandin infusionshould be initiated as rapidly as possible. Theemergency physician can use standard chest radi-ography and ECG information to narrow thediagnostic possibilities, but emergent echocardiog-raphy and pediatric cardiology consultation areindicated. If interfacility transport is required foraccess to subspecialty services, the stability of theneonate and capabilities of the transport teamshould be carefully considered, with particularassessment of need for prophylactic intubationbefore transport.

REFERENCES1. Kleinman ME, de Caen AR, Chameides L, et al. Pediatric

basic and advanced life support: 2010 international consen-sus on cardiopulmonary resuscitation and emergency car-diovascular care science with treatment recommendations.Pediatrics 2010;126:e1261.

2. Everett A. Cove Point Foundation Congenital Heart Disease.Available at: www.pted.org. Accessed June 10, 2011.

3. Hoffman JI, Kaplan S. The incidence of congenital heartdisease. J Am Coll Cardiol 2002;39:1890-900.

4. van Roekens CN, Zuckerberg AL. Emergency management ofhypercyanotic crises in tetralogy of Fallot. Ann Emerg Med1995;25:256-8.

5. Shaddy RE, Viney J, Judd VE, et al. Continuous intravenousphenylephrine infusion for treatment of hypoxemic spells intetralogy of Fallot. J Pediatr 1989;114:468-70.

6. Yetman AT, Freedom RM, McCrindle BW. Outcome incyanotic neonates with Ebstein's anomaly. Am J Cardiol1998;81:749-55.

7. Correa-Villasenor A, Ferencz C, Neill CA, et al. Ebstein'smalformation of the tricuspid valve: genetic and environ-mental factors. The Baltimore-Washington Infant StudyGroup. Teratology 1994;50:137-47.

8. MahleWT. A dangerous case of colic: anomalous left coronaryartery presenting with paroxysms of irritability. PediatrEmerg Care 1998;14:24-7.

9. Franklin WH, Dietrich AM, Hickey RW, et al. Anomalous leftcoronary artery masquerading as infantile bronchiolitis.Pediatr Emerg Care 1992;8:338-41.

10. Bonnemains L, Lambert V, Moulin-Zinch A, et al. Very earlycorrection of anomalous left coronary artery from thepulmonary artery improves intensive care management.Arch Cardiovasc Dis 2010;103:579-84.

11. Costa S, Zecca E, De RG, et al. Is serum troponin T a usefulmarker of myocardial damage in newborn infants withperinatal asphyxia? Acta Paediatr 2007;96:181-4.

12. Clark SJ, Newland P, Yoxall CW, et al. Sequential cardiactroponin T following delivery and its relationship withmyocardial performance in neonates with respiratory dis-tress syndrome. Eur J Pediatr 2006;165:87-93.

13. El-Khuffash AF, Molloy EJ. Influence of a patent ductusarteriosus on troponin T levels in preterm infants. J Pediatr2008;153:350-3.

14. Lewis AB, Freed MD, Heymann RA, et al. Side effects oftherapy with prostaglandin E1 in infants with criticalcongenital heart disease. Circulation 1981;64:893-8.

15. Lipshultz SE, Somers MJ, Lipsitz SR, et al. Serum cardiactroponin and subclinical cardiac status in pediatric chronicrenal failure. Pediatrics 2003;112:79-86.

16. Sirieix D, Delayance S, Paris M, et al. Trishydroxymethaneand sodium bicarbonate to buffer metabolic acidosis in anisolated heart model. Am J Respir Crit Care Med 1997;155:957-63.

17. Aschner JL, Poland RL. Sodium bicarbonate: basicallyuseless therapy. Pediatrics 2008;122:831-5.

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