Arrutmias en Pediatria

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Pediatric Arrhythmias

Debra Hanisch, RN, MSN, CPNP

During the past decade, our awareness and understanding of arrhythmias in children has expanded immensely. This reportdiscusses the more commonly encountered pediatric rhythm disturbances, including sinus node dysfunction, the various formsof supraventricular tachycardia, ventricular tachycardia, long QT syndrome, and the atrioventricular blocks. The electrocar-diographic characteristics, electrophysiological mechanisms, clinical presentation, and current acute and chronic managementoptions for each are described.Copyright 2001 by W.B. Saunders Company

N

ORMAL CONDUCTION IS characterized by

an impulse that is initiated by the sinoatrial(SA) node, located in the right atrium near the

superior vena cava junction, propagated through

the cardiac conduction system across the atria,

converging at the atrioventricular (AV) node, pro-

ceeding down the His bundle to the right and left

bundle branches, and finally spreading through-

out the Purkinje fibers to depolarize the ventricles

(Figure 1). Characteristic electrocardiographic

(ECG) findings of normal sinus rhythm include

upright P-waves and QRS complexes in leads I and

aVF. Age-appropriate parameters for heart rate, PR

interval, and QRS duration are presented in Table

1 (Liebman, 1982).

The majority of children who are diagnosed with

arrhythmias have structurally normal hearts. For

children with complex congenital heart disease,

advances in surgical and medical management

have resulted in improved survival. However,

these children may be at risk for developing early

and late postoperative arrhythmias. This report dis-

cusses the more common pediatric arrhythmias

found in both structurally normal hearts and in

patients with congenital heart disease. ECG char-

acteristics, electrophysiological mechanisms, clin-

ical presentation, and acute and chronic manage-ment options for each rhythm abnormality are

described.

SINUS NODE DYSFUNCTION

Sinus node dysfunction (SND) encompasses a

number of arrhythmias including sinus bradycar-

dia, sinus pauses or arrest, sinoatrial exit block,

escape rhythms, and brady-tachy syndromes. On

the ECG, sinus bradycardia has the appearance of

sinus rhythm, but at a slower rate than expected for

age (Table 2). Sinus pauses, sinus arrest, and exit

block produce electrical pauses in the rhythm.Junctional escape rhythms occur when the atrial

rate slows to the point where the AV nodes auto-

maticity takes over. Slow heart rates may predis-

pose the heart to certain tachyarrhythmias, such as

atrial flutter.

Typically, SND occurs as a result of surgical

injury to the sinoatrial node or its arterial supply.

Surgical procedures associated with a higher inci-

dence of SND include the Mustard or Senning

procedures for d-transposition of the great arteries,

the Fontan procedure for single ventricle physiol-

ogy, closure of atrial septal defects, and repair oftotal anomalous pulmonary venous return. How-

ever, whenever cannulation for cardiopulmonary

bypass is done near the superior vena cavaright

atrial junction, there is a risk for SND.

Nonsurgical causes of SND include right atrial

dilation due to pressure or volume overload. SND

may be seen in cardiomyopathies or inflammatory

conditions, such as myocarditis, pericarditis, and

rheumatic fever. Increased vagal tone and certain

drugs, especially antiarrhythmic agents, may result

in SND as well. In anorexia nervosa, resting heart

rates tend to be 20 beats/min slower than inmatched controls (Panagiotopoulos, McCrindle,

From the Lucile Packard Childrens Hospital at Stanford,

Palo Alto, CA.

Address reprint requests to Debra Hanisch, RN, MSN,

CPNP, Pediatric Cardiology, Lucile Packard Childrens Hos-

pital at Stanford, 750 Welch Rd., Suite #305, Palo Alto, CA

94304.

Copyright 2001 by W.B. Saunders Company

0882-5963/01/1605-0008$35.00/0

doi:10.1053/jpdn.2001.26571

351Journal of Pediatric Nursing, Vol 16, No 5 (October), 2001


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Hick, & Katzman, 2000). Conditioned athletes also

have slower-than-average resting heart rates. Mod-

ified criteria are used to diagnose SND in these

latter two populations.

Sinus node dysfunction may occur at any age.As a surgical complication, SND may occur im-

mediately after surgery or may not manifest for up

to 10 years or longer after surgery. Most children

with SND are asymptomatic. Of those who are

symptomatic, the most common symptoms appear

to be fatigue, exercise intolerance, dizziness, and

syncope. Sudden death is rare.

Acute management of the bradycardic child with

hemodynamic instability includes adequate venti-

lation, oxygenation, and administration of epineph-

rine (0.01 mg/kg) or, if the bradycardia is vagally

mediated, atropine (0.02 mg/kg; minimum dose 0.1mg). If there is no response to these medications,

temporary pacing should be instituted (Hazinski,

Cummins, & Field, 2000).

For long-term management, permanent pace-

maker therapy for SND is indicated when symp-

toms are associated with bradycardia or chrono-

tropic incompetence (Gregoratos et al., 1998).

Pacing may also be warranted in individuals with

brady-tachy syndrome, in which slowing of the

heart rate may mediate the onset of tachycardia. In

this situation, antibradycardia pacing either alone

or in combination with antitachycardia pacing maybe used. Prophylactic permanent pacing is a con-

sideration for patients with SND who are placed on

antiarrhythmic agents that prolong the QT interval,

such as amiodarone, to prevent further slowing of

the heart rate and/or pause-dependent torsades de

pointes (Martin & Kugler, 1999).

SUPRAVENTRICULAR TACHYCARDIA

Supraventricular tachycardia (SVT) refers to a

sustained tachyarrhythmia that originates above

Table 1. Normal Heart Rates, PR Intervals, and QRS Durations

in Children

Age

Heart Rate (bpm)PR Interval

(ms)QRS Duration

(ms)M Range

1 day 119 94-145 70-120 50-841-7 days 133 100-175 70-120 40-793-30 days 163 115-190 70-110 40-731-3 months 154 124-190 70-130 50-803-6 months 140 111-179 70-130 60-806-12 months 140 112-177 80-130 50-801-3 years 126 98-163 80-150 50-803-5 years 98 65-132 90-150 60-845-8 years 96 70-115 100-160 50-808-12 years 79 55-107 100-170 50-84

12-16 years 75 55-102 110-160 40-80

Adapted and reprinted with permission (Liebman, 1982).

Figure 1. Normal conductionsystem.

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the bundle of His. SVT is the most common ab-

normal tachyarrhythmia in children, with an esti-

mated incidence in the pediatric population of

0.1% to 0.4% (Ludomirsky & Garson, 1990). The

rhythm typically appears with an abrupt onset as a

regular, narrow QRS tachycardia. Rates vary from

130 to 300 beats/min depending on the patients

age and the SVT mechanism. On the ECG, the

QRS complex is usually normal in configuration,but in less than 10% of cases the QRS is wide due

to aberrant conduction to the ventricles (Ludomir-

sky & Garson, 1990).

Several SVT mechanisms have been identified.

The more common ones are described here (Figure

2). The vast majority of SVT rhythms are either

due to a re-entrant circuit, with or without an

accessory pathway, or an automatic ectopic focus.

Triggered activity accounts for a very small per-

centage of SVT.

Atrioventricular reciprocating tachycardia

(AVRT) is a common type of SVT that relies on at

least two electrical connections between the atriaand ventricles: the AV node and an accessory

pathway (more than one accessory pathway may

be present). Conduction proceeds antegrade down

one pathway and retrograde up the other to form a

Table 2. Sinus Bradycardia

ECG Criteriaa 24-Hour Ambulatory ECG Criteriaa

Age Group Heart Rate Age Group Heart Rate

Infants to 3 years 100 bpm Infants to 1 year of age 60 bpm sleeping; 80 bpm awakeChildren 3-9 years 60 bpm Children 1-6 years 60 bpmChildren 9-16 years 50 bpm Children 7-11 years 45 bpm

Adolescents 16 years 40 bpm Adolescents , young adu lts 40 bpmHighly trained athletes 30 bpm

aBased on data from Kugler, JD (Kugler, 1990).

Figure 2. Common mechanisms of SVT.

353PEDIATRIC ARRHYTHMIAS


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re-entrant circuit. Nearly 75% of the SVT rhythms

in children are mediated by accessory pathways.

The most common form of AVRT is orthodromic

reciprocating tachycardia, which involves ante-

grade conduction down the AV node to the ventri-

cles and retrograde conduction up the accessory

pathway to the atria. Antidromic reciprocating

tachycardia (down the accessory pathway, up the

AV node) occurs in less than 10% of patients.

Wolff-Parkinson-White (WPW) syndrome is a

frequently encountered type of AVRT. WPW is

characterized by a manifest pathway that is evident

on a 12-lead ECG during sinus rhythm. Pre-exci-

tation of the ventricle through the accessory path-

way (Kent bundle) appears as a delta wave, or

slurred upstroke into the QRS complex, along with

a shortened PR interval (Figure 3). There is an

increased incidence of WPW in patients with Eb-

steins anomaly, tricuspid atresia, double-outletright ventricle, and hypertrophy cardiomyopathy

(Van Hare, 1999). Among patients with AVRT,

about half have a concealed accessory pathway,

meaning that pre-excitation is not evident on the

12-lead ECG (Deal, 1998).

The permanent form of junctional reciprocating

tachycardia (PJRT) is a type of AVRT in which

the retrograde conduction through the accessory

pathway is slow, producing retrograde (inverted)

P-waves with a longer RP interval than is seen

in other types of AVRT. This slow conduction

through the accessory pathway contributes to theincessant nature of this form of SVT.

AV nodal re-entrant tachycardia (AVNRT) is

distinguished from AVRT in that, instead of an

accessory pathway, dual pathways exist within the

AV node. Typically, conduction proceeds ante-

grade down a slow pathway and retrograde up a

fast pathway to create a re-entrant circuit. On the

ECG, retrograde P-waves are buried within the

QRS complex. AVNRT accounts for nearly 15%

of SVT in the pediatric population, but rarely ap-

pears before the age of two years (Ko, Deal, Stras-

burger, & Benson, 1992). AVNRT is not associ-

ated with congenital heart disease (Deal, 1998).

Intra-atrial re-entrant tachycardia (IART),

commonly referred to as atrial flutter, is a re-

entrant tachycardia that is confined to the atria.

Propagation of IART relies on an electrical path-

way within the atria with both an area of slow

conduction and an anatomic obstruction that re-

sults in unidirectional block. This milieu for IART

exists after atrial surgery for congenital heart dis-

ease, such as the Mustard/Senning operation for

transposition of the great arteries, the Fontan pro-

cedure for single ventricle physiology, repair of

total anomalous pulmonary venous return, and

atrial septal defect closure. In fact, almost 95% of

atrial flutter diagnosed beyond infancy is associ-

ated with structural heart disease (Deal, 1998). On

ECG, characteristic saw-tooth waves (flutter

waves) are seen at rates of 200 to 400 bpm withvariable AV conduction (Figure 4).

Atrial ectopic tachycardia (AET) is a primary

atrial tachycardia that arises from an automatic

focus in the atria but outside the sinus node. Atrial

rates may range from 90 to 330 bpm with variable

AV block (Sokoloski, 1999). On ECG, distinct

P-waves are seen with a morphology that is differ-

ent from the normal sinus P-wave. AET is present

in only a small percentage of children with SVT

but has proven to be quite resistant to medical

management. As a rapid, incessant tachycardia,

AET may lead to a dilated cardiomyopathy that isusually reversible with successful abolition of the

automatic focus.

Junctional ectopic tachycardia (JET) is an au-

tomatic tachycardia that originates in the AV junc-

tion or His bundle. The ventricular rates generally

range from 150 to 300 bpm. The ECG may reveal

AV dissociation with the ventricular rate being

faster than the atrial rate (Figure 5). However, in

some cases, 1:1 VA conduction occurs, with the

retrograde P-wave superimposed on the QRS com-

plex. JET is encountered more frequently as a

Figure 3. Wolff-Parkinson-White (WPW).

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postoperative arrhythmia. The heart rate may start

out more slowly but then rapidly increases within a

few hours after cardiopulmonary bypass. Hemody-namic compromise occurs as a result of the fast

heart rate and loss of the atrial contribution to

ventricular filling (atrial kick). If not adequately

controlled, JET is associated with a high mortality

in the postoperative patient. Infrequently, JET may

present as a congenital arrhythmia with a familial

predilection.

The relative incidence of these different types of

SVT varies with age (Table 3). AVRT has a rela-

tively high incidence among newborns and infants,

with male patients affected more than female pa-

tients. In many of these infants SVT will sponta-neously resolve by 6 to 12 months of age, but over

30% will have recurrence later in life (Perry &

Garson, 1990). AVNRT is virtually unseen in ne-

onates but occurs more frequently with increasing

age. AVNRT represents over 50% of the SVT in

adults. The incidence of primary atrial tachycardias

remains fairly constant across all age groups.

Infants with SVT tend to present with nonspe-

cific symptoms such as irritability, lethargy, poor

feeding and, after 24 to 48 hours, signs of conges-

tive heart failure (CHF) (Table 4). In the presence

of associated congenital heart disease, CHF may

develop more quickly. In severe cases, hemody-namic compromise may occur and lead to respira-

tory distress, hypotension, and shock. The older

child with SVT may describe palpitations, a fast

heart rate, chest discomfort, or dizziness. In rare

instances, syncope or cardiac arrest may ensue.

Acute management of SVT depends on the pa-

tients age and condition. In the presence of shock

or cardiovascular collapse, immediate synchro-

nized cardioversion with 0.5 to 1.0 joule/kg is

warranted. In the more stable patient, 0.1 to 0.2

mg/kg of adenosine may be administered intrave-

nously by rapid bolus to induce transient AV block(Hazinski et al., 2000). If the SVT is a re-entrant

tachycardia that uses the AV node as part of its

circuit, adenosine will break the tachycardia. If not,

adenosine may at least be helpful in unveiling the

tachycardia mechanism during the brief time AV

conduction is interrupted (Figure 4). IART re-

sponds to either DC cardioversion or atrial over-

drive pacing. Automatic tachycardias (AET, JET)

do not respond to DC cardioversion or overdrive

pacing. Intravenous amiodarone has proven to be

Figure 4. Atrial flutter with 2:1 block.

Figure 5. Junctional ectopic tachycardia (JET).



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the most effective agent for the acute management

of these challenging automatic tachycardias. For

JET, atrial or dual-chamber pacing at a rate above

the JET rate can improve hemodynamics by estab-

lishing AV synchrony. Maintaining normothermia,

or even mild hypothermia, may lower the JET rate

to facilitate pacing therapy. For the very stable

pediatric patient with SVT, vagal maneuvers may

be attempted initially to terminate the tachycardia,

such as placing a bag of ice water over the face to

elicit the diving reflex, inducing rectal stimulation

with a thermometer (infants), or performing a Val-

salva maneuver (older child).

Chronic management of SVT also varies de-

pending on the patients age, symptoms, frequency

of tachycardia episodes, presence of structural

heart disease, and risk for sudden death. Most SVT

in infants involves an accessory pathway and can

usually be controlled with oral digoxin or propran-

olol to slow conduction across the AV node. If the

SVT is refractory to these agents, flecainide, so-

talol, or amiodarone may be effective but carry agreater risk of adverse effects. Combinations of

drugs may be needed in some cases. More than

90% of infants diagnosed with SVT before two

months of age will have spontaneous resolution of

their arrhythmia by eight months of age (Perry &

Garson, 1990). These patients are usually weaned

off their antiarrhythmic medications after 6 to 12

months of therapy but are monitored for late re-

currence. In the older child with infrequent epi-

sodes and mild symptoms, a management option

may be to do nothing. For others with more prob-

lematic tachycardia, chronic antiarrhythmic drug

therapy may be indicated. Radiofrequency (RF)

catheter ablation becomes a reasonable therapeutic

option in the school-aged child or adolescent. RF

ablation is performed in the cardiac catheterization

or electrophysiology laboratory with percutane-

ously inserted electrode catheters to map the elec-

trical pathways and an ablation catheter to create

strategically placed thermal lesions to interrupt im-

pulse conduction. The success rate with RF abla-

tion varies according to the type of SVT and insti-

tutional experience, but has been reported to be

83% to 96% (Kugler et al., 1994; Kugler, Danford,

Houston, & Felix, 1997). RF ablation has been

performed successfully in infants with SVT refrac-

tory to medical management but, because of theirsmall size, is associated with a much greater risk

for complications, such as AV block or perforation

of the heart.

VENTRICULAR TACHYCARDIA

Ventricular tachycardia (VT) is defined as three

or more consecutive premature ventricular com-

plexes (PVCs) at a rate greater than 120 beats/min

but usually less than 250 beats/min. The QRS

complexes are typically wide with AV dissociation

or, in rare cases, 1:1 retrograde VA conduction. VT

may be nonsustained (lasting less than 10 seconds)or sustained (lasting 10 seconds or longer). Mono-

morphic VT refers to tachycardia in which all the

QRS complexes have a similar morphology, in

contrast to polymorphic VT with multiform com-

plexes. Torsades de pointes (twisting of the

points) is a type of polymorphic VT characterized

by rapid, wide, undulating QRS complexes that

appear to be spiraling around an axis (Figure 6).

Table 3. Age-Related Incidence of SVTa

Age AVRT AVNRTPrimary Atrial Tachycardia

(IART, AET)

Prenatal/Neonate 80-85% 0% 15-20%Infant 80% 5% 15%1-5 years 65% 20-25% 10-15%

6-10 years 60% 30% 10-15%Adolescent 65-70% 20% 15%

aBased on data from Ko et al. (Ko et al., 1992).

Table 4. Differentiating Supraventricular Tachycardia From Sinus Tachycardia

Supraventricular Tachycardia Sinus Tachycardia

History Nonspecific; lethargy or i rritabi lity, poorfeeding, tachypnea, diaphoresis, pallor

Suggestive of volume loss, vomiting,diarrhea, blood loss, or febrile illness

Examination Signs of congestive heart failure: tachypnea,moist crackles, increased respiratoryeffort, poor perfusion, hepatomegaly

Consistent with dehydration, fever, or bloodloss; clear lungs, normal liver; may bedue to CHF in congenital heart disease

ECG Abrupt onset, heart rate 220 bpm,regular R-R intervals, P-waves seen in50-60% with abnormal axis, narrowQRS in 90% of SVTs

Gradual onset, heart rate usually less than200 bpm, variable R-R intervals, normalP-wave axis, narrow QRS

Chest radiograph May have an enlarged heart, signs ofpulmonary edema

Small or normal heart, clear lung fields(unless congenital heart disease present)

Echocardiogram May have ventricular dilat ion or dysfunction Usual ly normal

Adapted and reprinted with permission from Hanisch, D. (Hanisch & Perron, 1992).

356 DEBRA HANISCH


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Mechanisms for VT are not as well described as

for SVT, but appear to include re-entry (similar to

IART), abnormal automaticity, and triggered ac-

tivity.

The incidence of VT in the pediatric population

is unknown, but accounts for about 6% of patients

followed for tachyarrhythmia (Dick & Russell,

1998). The causes of VT in children are similar tothose for PVCs. VT may be associated with severe

electrolyte or metabolic abnormalities, hypoxia,

hypothermia, or drug toxicity. Cardiac conditions

such as cardiomyopathy, myocarditis, arrhythmo-

genic right ventricular dysplasia, and ventricular

tumors (rhabdomyomas, hamartomas) may create a

substrate for VT. Surgery for congenital heart dis-

ease, particularly procedures that involve a ventric-

ulotomy (i.e., tetralogy of Fallot repair) have been

associated with an increased risk for early and late

postoperative VT. Another recognized cause of VT

is congenital or acquired long QT syndrome.VT may present at any age and with varying

degrees of symptoms. Some children may present

with minimal symptoms despite their tachycardia;

however, most children will be symptomatic. In-

fants may be lethargic, tachypneic, and pale, and

may feed poorly. Mottling or cyanosis may be

present as well. Older children report palpitations,

chest discomfort, dizziness, nausea, or syncope. In

many instances, the child initially presents after

resuscitation from sudden cardiac death.

Acute management of VT in the unstable patient

should be focused on rapid termination of the

arrhythmia with synchronized cardioversion (0.5 to

1.0 joules/kg) or, if pulseless, defibrillation (2 to 4

joules/kg) (Hazinski et al., 2000). Intravenous li-

docaine, procainamide, or amiodarone may be

used to supress PVCs and further occurrences of

VT. Careful attention to maintaining normal elec-

trolyte values is necessary in the postresuscitation

period. In extreme cases of uncontrollable inces-

sant VT, extracorporeal membrane oxygenation(ECMO) support or a ventricular assist device may

be required.

Chronic management options for VT are based

on the childs age and clinical condition. Antiar-

rhythmic drug therapy may be successful in sup-

pressing ventricular ectopy in postoperative pa-

tients; however, the potential for proarrhythmia

and depression of ventricular function must be

recognized. An implantable pacemaker/cardio-

verter-defibrillator (ICD) device, with or without

concomitant drug therapy, is indicated for selected

patients with cardiomyopathy, long QT syndrome,life-threatening VT, and resuscitated sudden car-

diac death. RF ablation has been employed suc-

cessfully in some patients with discrete arrhythmo-

genic foci (Silka & Garson, 1999). For others,

surgical intervention either cryoablation, revi-

sion of previous congenital heart surgery, removal

of a cardiac tumor, or cardiac transplantmay be

necessary (Dick & Russell, 1998).

LONG QT SYNDROME

Congenital long QT syndrome (LQTS) is an

inherited disorder that affects the ion channels in

the heart, resulting in abnormal ventricular repo-

Figure 6. Torsades de pointes.

Figure 7. Mobitz I AV block (Wenckebach).



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larization and an increased risk for life-threatening

arrhythmias. LQTS is characterized by prolonga-

tion of the QT interval on ECG, usually measuring

greater than 440 to 460 ms. The diagnosis of

LQTS, however, is not based solely on the pres-

ence of a prolonged QT interval, but on additional

ECG findings, clinical presentation, and family

history. Typically on ECG, abnormal T-wave mor-

phology is present and may reflect the specific ion

channel that is affected. Patients with LQTS tend

to have abnormally low resting heart rates for their

age. A documented episode of torsades de pointes

lends further support to the diagnosis of LQTS.

Clinically, 60% of patients present with symptoms.

These symptoms include syncope or presyncope

(often associated with exercise, noise, or stress),

palpitations, seizure activity, and cardiac arrest.

Also, in 60% of cases, the family history is positive

for either a family member diagnosed with LQTSor a sudden, unexplained premature death.

The incidence of LQTS is estimated to be 1 in

5,000 to 10,000, with a higher prevalence in female

patients in the adult age group, but a nearly equal

gender distribution in children. Male patients tend

to present at an earlier age and more often with

sudden cardiac death (Locati et al., 1998). Several

clinical associations have been identified with

LQTS, including congenital AV block (5%), con-

genital deafness (4.5%), congenital heart disease

(12%), and syndactyly (Garson et al., 1993; Marks,

Trippel, & Keating, 1995). Jervell and Lange-Nielson syndrome represents the autosomal reces-

sive form of LQTS and is associated with congen-

ital deafness. Romano-Ward syndrome refers to the

autosomal dominant form of LQTS. The specific

types of LQTS that have been identified are listed

in Table 5. Approximately 50% of patients have

LQT1, 45% have LQT2, and 5% have LQT3. The

remaining types are relatively rare.

Management of LQTS is individualized, with

consideration given to the patients age and risk

factors. Typically, drug therapy with beta blocking

agents (propranolol, atenolol) is instituted. The use

of sodium channel blockers (mexiletine, pheny-

toin) for patients with identified LQT3 has been

advocated (Schwartz et al., 1995). Limited success

has been reported with potassium supplements and

spironolactone in selected patients with LQT2

(Compton et al., 1996). Pacemaker therapy is use-

ful in combination with beta blockade to pre-

vent bradycardia and pause-dependent torsades de

pointes. Increasing the heart rate with pacing also

helps to shorten the QT interval in these patients.

ICD placement is indicated for those who have

experienced a previous cardiac arrest or have failed

drug therapy. Tiered therapy consisting of beta

blockade and implantation of a pacemaker/ICD is

considered appropriate for high-risk patients. In

addition, the LQTS patient is instructed to avoid

triggers such as competitive athletics (LQT1), loudnoises (LQT2), hypokalemia, and drugs that cause

QT prolongation.

ATRIOVENTRICULAR BLOCKS

Atrioventricular (AV) block describes delayed or

incomplete conduction of impulses through the AV

node. Three degrees of AV block are recognized.

First-degree AV block is defined as prolonged

conduction through the AV node; this produces a

prolonged PR interval on the ECG, but there is

consistent 1:1 AV conduction. Second-degree AV

block has two forms: Mobitz I and Mobitz II.Mobitz type I AV block, also known as Wencke-

bach, is recognized on the ECG by its characteris-

tic pattern of a gradually lengthening PR inter-

val followed by a nonconducted P-wave (dropped

beat) (Figure 7). In Mobitz type II AV block, there

is intermittent failure of the P-wave to be con-

ducted, but wherever measurable PR intervals oc-

cur, they are consistent and do not lengthen. Gen-

erally, Mobitz II AV block produces a fixed ratio

of P-waves to QRS complexes (2:1 or 3:1), but

occasionally the AV block is variable. Third-de-

gree AV block is defined as complete failure of the

atrial impulses to be conducted to the ventricles.On the ECG, AV dissociation is seen in which the

atrial rate is faster than the ventricular rate.

AV block may be congenital or acquired. Con-

genital AV block is estimated to have an incidence

of 1 in 22,000 live births (Ross & Gillette, 1999).

Approximately 25% to 30% of these children have

associated congenital heart disease, most com-

monly 1-transposition of the great arteries with

ventricular inversion. In addition, there appears to

be a strong association between SS-A/Ro or SS-

Table 5. Genes Associated With Low QT Syndrome

(Ackerman, 1998)

LQTS Gene Chromosome Ion Channel

LQT1 KVLQT1 11p15.5 K

LQT2 HERG 7q35-36 K

LQT3 SCN5A 3q21-24 Na

LQT4 Unknown 4q25-27 UnknownLQT5 KCNE1 (MinK) 21q22.1-22.2 K

LQT6 MiRPI 21 KaJLN1 KVLQT1 11p15.5 KaJLN2 KCNE1 (MinK) 21q22.1-22.2 K

Data from Ackerman, 1998.aAssociated with congenital deafness.

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Table 6. Nursing Care of the Pediatric Arrhythmia Patient

Arrhythmia Clinical Symptoms Acute Management Chronic Management Parent/Patient Education

Sinus nodedysfunction

Slow heart rateIrregular heart beatFatigueExercise intolerance

DizzinessSyncope

Monitor rhythm andhemodynamic status

If unstable:Ventilate, oxygenate

EpinephrineAtropineIsoproterenololTemporary pacing

Pacemaker How to check pulse rateReport symptoms to cardiologistPacemaker education if device

is implanted

Supraventriculartachycardia

Infant:Irritability,

lethargyPoor feedingPallorSweatingCHF


If stable:Vagal maneuversOverdrive pacing

Adenosinemay be diagnosticand/or therapeutic (0.1-0.2 mg rapid IV bolus)

Medications:Digoxin for non-WPW onlyPropranololAtenololFlecainideSotalolAmiodarone

How to check pulse rateReport symptoms to cardiologistHow to perform vagal

maneuvers (check withcardiologist first)

If symptomatic, go toemergency room

Older child:PalpitationsFast heart rate

Chest discomfortDizziness

If unstable:Synchronized cardioversion

(0.5-1.0 joule/kg)For JET,

IV amiodarone Overdrive pacing

RF ablation Medication teaching as neededProcedural teaching if RF

ablation is planned

Ventriculartachycardia

Cardiac arrest Monitor rhythm andhemodynamic status

Medications:Amiodarone

How to check pulse rateHow to perform CPR

Infant:LethargyTachypneaPallorPoor feeding

CPR if neededSynchronized cardioversion

(0.5-1.0 joules/kg)If pulseless, defibrillation (2-4

joules/kg)

Beta-blockersVerapamil (in Verapamil-

sensitive VT)

Call 911 in the event ofsyncope or arrest

Medication teaching as neededAvoid medications that cause

QT prolongationOlder child:

PalpitationsChest discomfort

DizzinessNauseaSyncope

IV medications:AmiodaroneLidocaine

ProcainamideCorrect electrolyte imbalanceECMO or VAD for uncontrolled

incessant VT

RF ablationICD

Procedural teaching if ICD isplanned

Activity restrictions as

prescribed by cardiologist

Long QTsyndrome

Syncope/presyncopeoftenassociated withexercise, noise,or stress

PalpitationsSeizuresCardiac arrest


For Torsades de Pointes:Initiate CPRSynchronized cardioversionAdminister IV beta blocker

(Esmolol)Temporary overdrive pacing

to suppress VT

Medications:Beta blockers

PropranololAtenolol

?Alpha blockers?Na or Ca2 ion-channel

blockersPacemakerICD

How to check pulse rateHow to perform CPRCall 911 in the event of

syncope or arrestFamily members need ECGs to

measure QT (hereditary)Medication teachingProcedural teaching if

pacemaker or ICD isplanned

Avoid triggers:Competitive athleticsLoud noises (LQT2)HypokalemiaMedications that cause QT

prolongation

AV block(2 or 3)

CHFFatigueExercise intoleranceDizzinessSyncope

Temporary pacemaker Pacemaker How to check pulse rateHow to perform CPR if

pacemaker dependentProcedural teaching for

pacemaker implantPacemaker education,

emphasize no contactsports

Call 911 in the event ofsyncope or arrest



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B/La autoantibodies in the mother (present in col-

lagen vascular diseases such as lupus erythemato-

sis) and the development of congenital AV block

in the child (Waltuck & Buyon, 1994). Surgical

AV block occurs as a complication in congenital

heart surgery because of injury to the AV node or

His bundle. Certain procedures, such as closure of

an AV septal defect or ventricular septal defect,

tetralogy of Fallot repair, subaortic resection oraortic valve replacement, carry a higher risk for

surgical AV block. In the current era of congenital

heart surgery, the incidence of permanent AV

block is 3% or less for these procedures (Friedman,

1998). Inflammation, as seen with myocarditis,

rheumatic fever, or Lyme disease, is another cause

for acquired AV block.

Symptoms seen in children with AV block de-

pend on the ventricular rate. Children with first-

degree or second-degree Mobitz I AV block are

generally asymptomatic. However, the fetus with

complete AV block may present with hydrops and

necessitate early delivery and intervention. CHFmay be seen in infants with slow ventricular rates,

especially in the presence of associated congenital

heart defects. Older children may complain of fa-

tigue, exercise intolerance, dizziness, or, in some

cases, syncope. Sudden death has been reported. A

chest radiograph may reveal cardiomegaly in pa-

tients with long-standing AV block due to the

chronically slow hearts attempt to compensate by

augmenting the stroke volume.

Pacemaker therapy is clearly indicated for

symptomatic children with second-degree Mobitz

II and third-degree complete AV block. In postop-

erative patients, the AV block may be transient, so

temporary pacing is employed for the first 10 to 14

days. If the AV block persists beyond this period,

permanent pacing is warranted. Much controversy

exists over the proper time to intervene with pacing

in the asymptomatic child with congenital AV

block (Friedman, 1995). With advances in devicetechnology and pacing lead design, implanting

pacemakers in young infants and children has be-

come much safer and more practical.

NURSING RESPONSIBILITIES

The bedside nurse is in a crucial position to

identify rhythm disturbances in pediatric patients.

Quick determination of the childs hemodynamic

status at the onset of an abnormal rhythm with

ongoing assessments throughout the course of the

arrhythmia is key to guiding therapy. Monitoring

the ECG and obtaining clear rhythm strips to doc-

ument both normal and abnormal rhythms contrib-ute to making an accurate arrhythmia diagnosis.

When antiarrhythmic drugs are used, the nurse

must be aware of possible adverse effects, includ-

ing the potential for proarrhythmia. An awareness

and understanding of newer treatment modalities,

including RF ablation techniques and device ther-

apy, has important implications for patient care as

well (Tables 6 and 7).

Patient education is a vital component of the

nurses role in caring for these children and their

Table 7. Internet Resources

Organization Website Comments

American Heart Association (AHA) www.americanheart.org Professional and lay information on manycardiac conditions, including arrhythmias

North American Society of Pacingand Electrophysiology (NASPE)

www.NASPE.org Professional and lay information on arrhythmias,RF ablation, medications, and device therapy

The Heart of PediatricElectrophysiology (HOPE)

www.rhythmsofhope.org Organization was formed in 1999 to provideeducation and support to families and healthprofessionals.

Website not yet available.Toll-free phone number: 877-394-HOPE

SADS Foundation (SuddenArrhythmic Death Syndrome)

www.sads.org Nonprofit organization provides information onLong QT Syndrome, including acomprehensive listing of medications thatcause QT prolongation

Cardiac Arrhythmia Research andEducation Foundation, Inc. (CARE)

www.longqt.com Nonprofit organization provides information onLong QT Syndrome

The Childrens Health InformationNetwork

www.tchin.org Internet resource for professionals and familiesproviding information on various aspects ofcongenital heart disease, includingarrhythmias

Physicians Desk Reference PDR.net Professional and lay information on medications,including antiarrhythmic drugs

360 DEBRA HANISCH


11/12

families. Parents and patients need to learn how to

check a pulse rate, how to recognize signs and

symptoms associated with arrhythmias and side

effects of prescribed antiarrhythmic agents, what

to do if signs or symptoms occur, what types of

activity should be restricted, and, in some cases,

how to perform cardiopulmonary resuscitation

(CPR). Patients at risk for syncope or cardiac arrest

should be encouraged to obtain a MedicAlert

bracelet (MedicAlert, Turlock, CA). Psychosocial

issues need to be addressed as well. Parents and

patients may be afraid of a cardiac arrest, espe-

cially if there is pacemaker-dependency or a family

history of sudden cardiac death. Children and ad-

olescents with implanted pacemakers or defibrilla-

tors often express concerns related to repeated sur-

gical procedures and the resultant scars and

visibility of the implanted device. These patients

frequently express a need to be accepted by their

peers and be treated normally (Zeigler & Corbett,

1995). In some cases, referral to professional coun-

seling may be beneficial. Effective and safe man-

agement of young patients with arrhythmias is

contingent upon a comprehensive team approach

that includes not only the health care professionals,

but also the caretakers of these special children.

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