Pediatric arrhythmias.pdf

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

NORMAL CONDUCTION IS characterized byan impulse that is initiated by the sinoatrial

(SA) node, located in the right atrium near thesuperior vena cava junction, propagated throughthe cardiac conduction system across the atria,converging at the atrioventricular (AV) node, pro-ceeding down the His bundle to the right and leftbundle branches, and finally spreading through-out the Purkinje fibers to depolarize the ventricles(Figure 1). Characteristic electrocardiographic(ECG) findings of normal sinus rhythm includeupright P-waves and QRS complexes in leads I andaVF. Age-appropriate parameters for heart rate, PRinterval, and QRS duration are presented in Table1 (Liebman, 1982).

The majority of children who are diagnosed witharrhythmias have structurally normal hearts. Forchildren with complex congenital heart disease,advances in surgical and medical managementhave resulted in improved survival. However,these children may be at risk for developing earlyand late postoperative arrhythmias. This report dis-cusses the more common pediatric arrhythmiasfound in both structurally normal hearts and inpatients with congenital heart disease. ECG char-acteristics, electrophysiological mechanisms, clin-ical presentation, and acute and chronic manage-ment options for each rhythm abnormality aredescribed.

SINUS NODE DYSFUNCTION

Sinus node dysfunction (SND) encompasses anumber of arrhythmias including sinus bradycar-dia, sinus pauses or arrest, sinoatrial exit block,escape rhythms, and brady-tachy syndromes. Onthe ECG, sinus bradycardia has the appearance ofsinus rhythm, but at a slower rate than expected for

age (Table 2). Sinus pauses, sinus arrest, and exitblock produce electrical pauses in the rhythm.Junctional escape rhythms occur when the atrialrate slows to the point where the AV node’s auto-maticity takes over. Slow heart rates may predis-pose the heart to certain tachyarrhythmias, such asatrial flutter.

Typically, SND occurs as a result of surgicalinjury to the sinoatrial node or its arterial supply.Surgical procedures associated with a higher inci-dence of SND include the Mustard or Senningprocedures 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 cardiopulmonarybypass is done near the superior vena cava–rightatrial junction, there is a risk for SND.

Nonsurgical causes of SND include right atrialdilation due to pressure or volume overload. SNDmay be seen in cardiomyopathies or inflammatoryconditions, such as myocarditis, pericarditis, andrheumatic fever. Increased vagal tone and certaindrugs, especially antiarrhythmic agents, may resultin SND as well. In anorexia nervosa, resting heartrates tend to be 20 beats/min slower than inmatched controls (Panagiotopoulos, McCrindle,

From the Lucile Packard Children’s Hospital at Stanford,Palo Alto, CA.

Address reprint requests to Debra Hanisch, RN, MSN,CPNP, Pediatric Cardiology, Lucile Packard Children’s Hos-pital at Stanford, 750 Welch Rd., Suite #305, Palo Alto, CA94304.

Copyright © 2001 by W.B. Saunders Company0882-5963/01/1605-0008$35.00/0doi:10.1053/jpdn.2001.26571

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

Hick, & Katzman, 2000). Conditioned athletes alsohave slower-than-average resting heart rates. Mod-ified criteria are used to diagnose SND in theselatter 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 upto 10 years or longer after surgery. Most childrenwith SND are asymptomatic. Of those who aresymptomatic, the most common symptoms appearto be fatigue, exercise intolerance, dizziness, andsyncope. Sudden death is rare.

Acute management of the bradycardic child withhemodynamic instability includes adequate venti-lation, oxygenation, and administration of epineph-rine (0.01 mg/kg) or, if the bradycardia is vagallymediated, 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 withbrady-tachy syndrome, in which slowing of theheart rate may mediate the onset of tachycardia. Inthis situation, antibradycardia pacing either aloneor in combination with antitachycardia pacing maybe used. Prophylactic permanent pacing is a con-sideration for patients with SND who are placed onantiarrhythmic agents that prolong the QT interval,such as amiodarone, to prevent further slowing ofthe heart rate and/or pause-dependenttorsades depointes(Martin & Kugler, 1999).

SUPRAVENTRICULAR TACHYCARDIA

Supraventricular tachycardia (SVT) refers to asustained tachyarrhythmia that originates above

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

352 DEBRA HANISCH

the bundle of His. SVT is the most common ab-normal tachyarrhythmia in children, with an esti-mated incidence in the pediatric population of0.1% to 0.4% (Ludomirsky & Garson, 1990). Therhythm typically appears with an abrupt onset as aregular, narrow QRS tachycardia. Rates vary from130 to 300 beats/min depending on the patient’sage and the SVT mechanism. On the ECG, theQRS complex is usually normal in configuration,but in less than 10% of cases the QRS is wide dueto aberrant conduction to the ventricles (Ludomir-sky & Garson, 1990).

Several SVT mechanisms have been identified.

The more common ones are described here (Figure2). The vast majority of SVT rhythms are eitherdue to a re-entrant circuit, with or without anaccessory 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 atleast two electrical connections between the atriaand ventricles: the AV node and an accessorypathway (more than one accessory pathway maybe present). Conduction proceeds antegrade downone 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 bpmAdolescents . 16 years ,40 bpm Adolescents, young adults ,40 bpm

Highly trained athletes ,30 bpm

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

Figure 2. Common mechanisms of SVT.

353PEDIATRIC ARRHYTHMIAS

re-entrant circuit. Nearly 75% of the SVT rhythmsin children are mediated by accessory pathways.The most common form of AVRT isorthodromicreciprocating tachycardia,which involves ante-grade conduction down the AV node to the ventri-cles and retrograde conduction up the accessorypathway to the atria. Antidromic reciprocatingtachycardia (down the accessory pathway, up theAV node) occurs in less than 10% of patients.

Wolff-Parkinson-White (WPW) syndrome is afrequently encountered type of AVRT. WPW ischaracterized by a manifest pathway that is evidenton 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, orslurred upstroke into the QRS complex, along witha shortened PR interval (Figure 3). There is anincreased incidence of WPW in patients with Eb-stein’s 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 the12-lead ECG (Deal, 1998).

Thepermanent form of junctional reciprocatingtachycardia(PJRT) is a type of AVRT in whichthe retrograde conduction through the accessorypathway is slow, producing retrograde (inverted)P-waves with a longer RP interval than is seenin other types of AVRT. This slow conductionthrough the accessory pathway contributes to theincessant nature of this form of SVT.

AV nodal re-entrant tachycardia(AVNRT) isdistinguished from AVRT in that, instead of anaccessory pathway, dual pathways exist within theAV node. Typically, conduction proceeds ante-grade down a slow pathway and retrograde up afast pathway to create a re-entrant circuit. On theECG, retrograde P-waves are buried within theQRS 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 asatrial 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 slowconduction and an anatomic obstruction that re-sults in unidirectional block. This milieu for IARTexists after atrial surgery for congenital heart dis-ease, such as the Mustard/Senning operation fortransposition of the great arteries, the Fontan pro-cedure for single ventricle physiology, repair oftotal anomalous pulmonary venous return, andatrial septal defect closure. In fact, almost 95% ofatrial flutter diagnosed beyond infancy is associ-ated with structural heart disease (Deal, 1998). OnECG, characteristic saw-tooth waves (flutterwaves) are seen at rates of 200 to 400 bpm withvariable AV conduction (Figure 4).

Atrial ectopic tachycardia(AET) is a primaryatrial tachycardia that arises from an automaticfocus in the atria but outside the sinus node. Atrialrates may range from 90 to 330 bpm with variableAV block (Sokoloski, 1999). On ECG, distinctP-waves are seen with a morphology that is differ-ent from the normal sinus P-wave. AET is presentin only a small percentage of children with SVTbut has proven to be quite resistant to medicalmanagement. As a rapid, incessant tachycardia,AET may lead to a dilated cardiomyopathy that isusually reversible with successful abolition of theautomatic focus.

Junctional ectopic tachycardia(JET) is an au-tomatic tachycardia that originates in the AV junc-tion or His bundle. The ventricular rates generallyrange from 150 to 300 bpm. The ECG may revealAV dissociation with the ventricular rate beingfaster than the atrial rate (Figure 5). However, insome cases, 1:1 VA conduction occurs, with theretrograde P-wave superimposed on the QRS com-plex. JET is encountered more frequently as a

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

354 DEBRA HANISCH

postoperative arrhythmia. The heart rate may startout more slowly but then rapidly increases within afew hours after cardiopulmonary bypass. Hemody-namic compromise occurs as a result of the fastheart rate and loss of the atrial contribution toventricular filling (atrial kick). If not adequatelycontrolled, JET is associated with a high mortalityin the postoperative patient. Infrequently, JET maypresent as a congenital arrhythmia with a familialpredilection.

The relative incidence of these different types ofSVT 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 over30% will have recurrence later in life (Perry &Garson, 1990). AVNRT is virtually unseen in ne-onates but occurs more frequently with increasingage. AVNRT represents over 50% of the SVT inadults. The incidence of primary atrial tachycardiasremains fairly constant across all age groups.

Infants with SVT tend to present with nonspe-cific symptoms such as irritability, lethargy, poorfeeding and, after 24 to 48 hours, signs of conges-

tive heart failure (CHF) (Table 4). In the presenceof associated congenital heart disease, CHF maydevelop more quickly. In severe cases, hemody-namic compromise may occur and lead to respira-tory distress, hypotension, and shock. The olderchild with SVT may describe palpitations, a fastheart rate, chest discomfort, or dizziness. In rareinstances, syncope or cardiac arrest may ensue.

Acute management of SVT depends on the pa-tient’s age and condition. In the presence of shockor cardiovascular collapse, immediate synchro-nized cardioversion with 0.5 to 1.0 joule/kg iswarranted. In the more stable patient, 0.1 to 0.2mg/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-entranttachycardia that uses the AV node as part of itscircuit, adenosine will break the tachycardia. If not,adenosine may at least be helpful in unveiling thetachycardia mechanism during the brief time AVconduction 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 overdrivepacing. Intravenous amiodarone has proven to be

Figure 4. Atrial flutter with 2:1 block.

Figure 5. Junctional ectopic tachycardia (JET).


the most effective agent for the acute managementof these challenging automatic tachycardias. ForJET, atrial or dual-chamber pacing at a rate abovethe JET rate can improve hemodynamics by estab-lishing AV synchrony. Maintaining normothermia,or even mild hypothermia, may lower the JET rateto facilitate pacing therapy. For the very stablepediatric patient with SVT, vagal maneuvers maybe attempted initially to terminate the tachycardia,such as placing a bag of ice water over the face toelicit the diving reflex, inducing rectal stimulationwith a thermometer (infants), or performing a Val-salva maneuver (older child).

Chronic management of SVT also varies de-pending on the patient’s age, symptoms, frequencyof tachycardia episodes, presence of structuralheart disease, and risk for sudden death. Most SVTin infants involves an accessory pathway and canusually be controlled with oral digoxin or propran-olol to slow conduction across the AV node. If theSVT is refractory to these agents, flecainide, so-talol, or amiodarone may be effective but carry agreater risk of adverse effects. Combinations ofdrugs may be needed in some cases. More than90% of infants diagnosed with SVT before twomonths of age will have spontaneous resolution oftheir arrhythmia by eight months of age (Perry &Garson, 1990). These patients are usually weanedoff their antiarrhythmic medications after 6 to 12months of therapy but are monitored for late re-

currence. In the older child with infrequent epi-sodes and mild symptoms, a management optionmay be to do nothing. For others with more prob-lematic tachycardia, chronic antiarrhythmic drugtherapy may be indicated. Radiofrequency (RF)catheter ablation becomes a reasonable therapeuticoption in the school-aged child or adolescent. RFablation is performed in the cardiac catheterizationor electrophysiology laboratory with percutane-ously inserted electrode catheters to map the elec-trical pathways and an ablation catheter to createstrategically 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 be83% to 96% (Kugler et al., 1994; Kugler, Danford,Houston, & Felix, 1997). RF ablation has beenperformed successfully in infants with SVT refrac-tory to medical management but, because of theirsmall size, is associated with a much greater riskfor complications, such as AV block or perforationof the heart.

VENTRICULAR TACHYCARDIA

Ventricular tachycardia(VT) is defined as threeor more consecutive premature ventricular com-plexes (PVCs) at a rate greater than 120 beats/minbut usually less than 250 beats/min. The QRScomplexes are typically wide with AV dissociationor, in rare cases, 1:1 retrograde VA conduction. VTmay be nonsustained (lasting less than 10 seconds)or sustained (lasting 10 seconds or longer).Mono-morphic VTrefers to tachycardia in which all theQRS complexes have a similar morphology, incontrast to polymorphic VT with multiform com-plexes. Torsades de pointes(“twisting of thepoints”) is a type of polymorphic VT characterizedby rapid, wide, undulating QRS complexes thatappear 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 irritability, 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 dilation or dysfunction Usually normal

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

356 DEBRA HANISCH

Mechanisms for VT are not as well described asfor SVT, but appear to include re-entry (similar toIART), abnormal automaticity, and triggered ac-tivity.

The incidence of VT in the pediatric populationis unknown, but accounts for about 6% of patientsfollowed for tachyarrhythmia (Dick & Russell,1998). The causes of VT in children are similar tothose for PVCs. VT may be associated with severeelectrolyte or metabolic abnormalities, hypoxia,hypothermia, or drug toxicity. Cardiac conditionssuch as cardiomyopathy, myocarditis, arrhythmo-genic right ventricular dysplasia, and ventriculartumors (rhabdomyomas, hamartomas) may create asubstrate for VT. Surgery for congenital heart dis-ease, particularly procedures that involve a ventric-ulotomy (i.e., tetralogy of Fallot repair) have beenassociated with an increased risk for early and latepostoperative VT. Another recognized cause of VTis congenital or acquired long QT syndrome.

VT may present at any age and with varyingdegrees of symptoms. Some children may presentwith minimal symptoms despite their tachycardia;however, most children will be symptomatic. In-fants may be lethargic, tachypneic, and pale, andmay feed poorly. Mottling or cyanosis may bepresent as well. Older children report palpitations,chest discomfort, dizziness, nausea, or syncope. Inmany instances, the child initially presents afterresuscitation from sudden cardiac death.

Acute management of VT in the unstable patientshould be focused on rapid termination of thearrhythmia with synchronized cardioversion (0.5 to

1.0 joules/kg) or, if pulseless, defibrillation (2 to 4joules/kg) (Hazinski et al., 2000). Intravenous li-docaine, procainamide, or amiodarone may beused to supress PVCs and further occurrences ofVT. Careful attention to maintaining normal elec-trolyte values is necessary in the postresuscitationperiod. In extreme cases of uncontrollable inces-sant VT, extracorporeal membrane oxygenation(ECMO) support or a ventricular assist device maybe required.

Chronic management options for VT are basedon the child’s age and clinical condition. Antiar-rhythmic drug therapy may be successful in sup-pressing ventricular ectopy in postoperative pa-tients; however, the potential for proarrhythmiaand depression of ventricular function must berecognized. An implantable pacemaker/cardio-verter-defibrillator (ICD) device, with or withoutconcomitant drug therapy, is indicated for selectedpatients 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, removalof a cardiac tumor, or cardiac transplant—may benecessary (Dick & Russell, 1998).

LONG QT SYNDROME

Congenital long QT syndrome(LQTS) is aninherited disorder that affects the ion channels inthe heart, resulting in abnormal ventricular repo-

Figure 6. Torsades de pointes.

Figure 7. Mobitz I AV block (Wenckebach).


larization and an increased risk for life-threateningarrhythmias. LQTS is characterized by prolonga-tion of the QT interval on ECG, usually measuringgreater than 440 to 460 ms. The diagnosis ofLQTS, however, is not based solely on the pres-ence of a prolonged QT interval, but on additionalECG findings, clinical presentation, and familyhistory. Typically on ECG, abnormal T-wave mor-phology is present and may reflect the specific ionchannel that is affected. Patients with LQTS tendto have abnormally low resting heart rates for theirage. A documented episode oftorsades de pointeslends 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 positivefor either a family member diagnosed with LQTSor a sudden, unexplained premature death.

The incidence of LQTS is estimated to be 1 in5,000 to 10,000, with a higher prevalence in femalepatients in the adult age group, but a nearly equalgender distribution in children. Male patients tendto present at an earlier age and more often withsudden cardiac death (Locati et al., 1998). Severalclinical associations have been identified withLQTS, 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 syndromerepresents the autosomal reces-sive form of LQTS and is associated with congen-ital deafness.Romano-Ward syndromerefers to theautosomal dominant form of LQTS. The specifictypes of LQTS that have been identified are listedin Table 5. Approximately 50% of patients haveLQT1, 45% have LQT2, and 5% have LQT3. Theremaining types are relatively rare.

Management of LQTS is individualized, withconsideration given to the patient’s age and risk

factors. Typically, drug therapy with beta blockingagents (propranolol, atenolol) is instituted. The useof sodium channel blockers (mexiletine, pheny-toin) for patients with identified LQT3 has beenadvocated (Schwartz et al., 1995). Limited successhas been reported with potassium supplements andspironolactone 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-dependenttorsades depointes.Increasing the heart rate with pacing alsohelps to shorten the QT interval in these patients.ICD placement is indicated for those who haveexperienced a previous cardiac arrest or have faileddrug therapy. Tiered therapy consisting of betablockade and implantation of a pacemaker/ICD isconsidered appropriate for high-risk patients. Inaddition, the LQTS patient is instructed to avoidtriggers such as competitive athletics (LQT1), loudnoises (LQT2), hypokalemia, and drugs that causeQT prolongation.

ATRIOVENTRICULAR BLOCKS

Atrioventricular (AV) blockdescribes delayed orincomplete conduction of impulses through the AVnode. Three degrees of AV block are recognized.First-degree AV block is defined as prolongedconduction through the AV node; this produces aprolonged PR interval on the ECG, but there isconsistent 1:1 AV conduction.Second-degreeAVblock 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 (droppedbeat) (Figure 7). In Mobitz type II AV block, thereis 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 ratioof P-waves to QRS complexes (2:1 or 3:1), butoccasionally the AV block is variable.Third-de-greeAV block is defined as complete failure of theatrial impulses to be conducted to the ventricles.On the ECG, AV dissociation is seen in which theatrial rate is faster than the ventricular rate.

AV block may be congenital or acquired. Con-genital AV block is estimated to have an incidenceof 1 in 22,000 live births (Ross & Gillette, 1999).Approximately 25% to 30% of these children haveassociated congenital heart disease, most com-monly 1-transposition of the great arteries withventricular inversion. In addition, there appears tobe 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 K1

LQT2 HERG 7q35-36 K1

LQT3 SCN5A 3q21-24 Na1

LQT4 Unknown 4q25-27 UnknownLQT5 KCNE1 (MinK) 21q22.1-22.2 K1

LQT6 MiRPI 21 K1

aJLN1 KVLQT1 11p15.5 K1

aJLN2 KCNE1 (MinK) 21q22.1-22.2 K1

Data from Ackerman, 1998.aAssociated with congenital deafness.

358 DEBRA HANISCH

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 intoleranceDizzinessSyncope

Monitor rhythm andhemodynamic status

If unstable:Ventilate, oxygenateEpinephrineAtropineIsoproterenololTemporary 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

Adenosine—may 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 rateChest discomfortDizziness

If unstable:Synchronized cardioversion

(0.5-1.0 joule/kg)For JET,

IV amiodarone 1

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 discomfortDizzinessNauseaSyncope

IV medications:AmiodaroneLidocaineProcainamide

Correct electrolyte imbalanceECMO or VAD for uncontrolled

incessant VT

RF ablationICD

Procedural teaching if ICD isplanned

Activity restrictions asprescribed 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?Na1 or Ca12 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


B/La autoantibodies in the mother (present in col-lagen vascular diseases such as lupus erythemato-sis) and the development of congenital AV blockin the child (Waltuck & Buyon, 1994). SurgicalAV block occurs as a complication in congenitalheart surgery because of injury to the AV node orHis bundle. Certain procedures, such as closure ofan AV septal defect or ventricular septal defect,tetralogy of Fallot repair, subaortic resection oraortic valve replacement, carry a higher risk forsurgical AV block. In the current era of congenitalheart surgery, the incidence of permanent AVblock is 3% or less for these procedures (Friedman,1998). Inflammation, as seen with myocarditis,rheumatic fever, or Lyme disease, is another causefor 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 aregenerally asymptomatic. However, the fetus withcomplete AV block may present with hydrops andnecessitate early delivery and intervention. CHFmay be seen in infants with slow ventricular rates,especially in the presence of associated congenitalheart defects. Older children may complain of fa-tigue, exercise intolerance, dizziness, or, in somecases, syncope. Sudden death has been reported. Achest radiograph may reveal cardiomegaly in pa-tients with long-standing AV block due to thechronically slow heart’s attempt to compensate byaugmenting the stroke volume.

Pacemaker therapy is clearly indicated for

symptomatic children with second-degree MobitzII and third-degree complete AV block. In postop-erative patients, the AV block may be transient, sotemporary pacing is employed for the first 10 to 14days. If the AV block persists beyond this period,permanent pacing is warranted. Much controversyexists over the proper time to intervene with pacingin the asymptomatic child with congenital AVblock (Friedman, 1995). With advances in devicetechnology and pacing lead design, implantingpacemakers in young infants and children has be-come much safer and more practical.

NURSING RESPONSIBILITIES

The bedside nurse is in a crucial position toidentify rhythm disturbances in pediatric patients.Quick determination of the child’s hemodynamicstatus at the onset of an abnormal rhythm withongoing assessments throughout the course of thearrhythmia is key to guiding therapy. Monitoringthe 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 nursemust be aware of possible adverse effects, includ-ing the potential for proarrhythmia. An awarenessand understanding of newer treatment modalities,including RF ablation techniques and device ther-apy, has important implications for patient care aswell (Tables 6 and 7).

Patient education is a vital component of thenurse’s 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 Children’s 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

families. Parents and patients need to learn how tocheck a pulse rate, how to recognize signs andsymptoms associated with arrhythmias and sideeffects of prescribed antiarrhythmic agents, whatto do if signs or symptoms occur, what types ofactivity should be restricted, and, in some cases,how to perform cardiopulmonary resuscitation(CPR). Patients at risk for syncope or cardiac arrestshould be encouraged to obtain a MedicAlertbracelet (MedicAlert, Turlock, CA). Psychosocialissues need to be addressed as well. Parents andpatients 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 andvisibility of the implanted device. These patientsfrequently express a need to be accepted by theirpeers 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 iscontingent upon a comprehensive team approachthat includes not only the health care professionals,but also the caretakers of these special children.

REFERENCESAckerman, M.J. (1998). The long QT syndrome: Ion channel

diseases of the heart.Mayo Clinic Proceedings, 73(3),250-269.Compton, S.J., Lux, R.L., Ramsey, M.R., Strelich, K.R.,

Sanguinetti, M.C., Green, L.S., Keating, M.T., & Mason, J.W.(1996). Genetically defined therapy of inherited long-QT syn-drome: Correction of abnormal repolarization by potassium.Circulation, 94(5),1018-1022.

Deal, B.J. (1998). Supraventricular tachycardia mechanismsand natural history. In B.J. Deal, G.S. Wolff, & H. Gelband(Eds.), Current Concepts in Diagnosis and Management ofArrhythmias in Infants and Children(pp. 117-143). Armonk,NY: Futura Publishing.

Dick, M.I., & Russell, M.W. (1998). Ventricular tachycardia.In B.J. Deal, G.S. Wolff, & H. Gelband (Eds.),Current Con-cepts in Diagnosis and Management of Arrhythmias in Infantsand Children(pp. 181-222). Armonk, NY: Futura Publishing.

Friedman, R.A. (1995). Congenital AV block: Pace me nowor pace me later?Circulation, 92(3),283-285.

Friedman, R.A. (1998). Sinus and atrioventricular conductiondisorders. In B.J. Deal, G.S. Wolff, & H. Gelband (Eds.),Current Concepts in Diagnosis and Management of Arrhyth-mias in Infants and Children(pp. 89-116). Armonk, NY: FuturaPublishing.

Garson, A.J., Dick, M.I., Fournier, A., Gillette, P.C., Ham-ilton, R., Kugler, J.D., Van Hare, G.F.I., Vetter, V., & Vick,G.W.I. (1993). The long QT syndrome in children: An interna-tional study of 287 patients.Circulation, 87(6),1866-1872.

Gregoratos, G., Cheitlin, M., Conill, A., Epstein, A., Fellows,C., Ferguson, T.J., Freedman, R., Hlatky, M., Naccarelli, G.,Saksena, S., Schlant, R., & Silka, M. (1998). ACC/AHA Guide-lines for implantation of cardiac pacemakers and antiarrhythmiadevices: A report of the American College of Cardiology/American Heart Association task force on practice guidelines(committee on pacemaker implantation).Journal of the Amer-ican College of Cardiology, 31,1175-1209.

Hanisch, D.G., & Perron, L. (1992). Complex dysrhythmiasin infants and children.AACN Clinical Issues in Critical CareNursing, 3(1),255-269.

Hazinski, M.F., Cummins, R.O., & Field, J.M. (Eds.). (2000).2000 Handbook of Emergency Cardiovascular Care for Health-care Providers.Dallas: American Heart Association.

Ko, J.K., Deal, B.J., Strasburger, J.F., & Benson, D.W.J.(1992). Supraventricular tachycardia mechanisms and their agedistribution in pediatric patients.American Journal of Cardiol-ogy, 69(12),1028-1032.

Kugler, J.D. (1990). Sinus node dysfunction. In P. Gillette &A.J. Garson (Eds.),Pediatric Arrhythmias: Electrophysiologyand Pacing(pp. 250-300). Philadelphia: WB Saunders.

Kugler, J.D., Danford, D.A., Deal, B.J., Gillette, P.C., Perry,J.C., Silka, M.J., Van Hare, G.F., & Walsh, E.P. (1994). Ra-diofrequency catheter ablation for tachyarrhythmias in children

and adolescents.The New England Journal of Medicine,330(21),1481-1487.

Kugler, J.D., Danford, D.A., Houston, K., & Felix, G. (1997).Radiofrequency catheter ablation for paroxysmal supraventric-ular tachycardia in children and adolescents without structuralheart disease.American Journal of Cardiology, 80(11),1438-1443.

Liebman, J. (1982). Tables of normal standards. In J. Lieb-man, R. Plonsey, & P.C. Gillette (Eds.),Pediatric Electrocar-diography(pp. 82-133). Baltimore: Williams & Wilkins.

Locati, E.H., Zareba, W., Moss, A.J., Schwartz, P.J., Vincent,G.M., Lehmann, M.H., Towbin, J.A., Priori, S.G., Napolitano,C., Robinson, J.L., Andrews, M., Timothy, K., & Hall, W.J.(1998). Age- and sex-related differences in clinical manifesta-tions in patients with congenital long-QT syndrome: Findingsfrom the international LQTS registry.Circulation, 97(22),2237-2244.

Ludomirsky, A., & Garson, A. (1990). Supraventriculartachycardia. In P.C. Gillette & A.J. Garson (Eds.),PediatricArrhythmias: Electrophysiology and Pacing(pp. 380-426).Philadelphia: W.B. Saunders Company.

Marks, M.L., Trippel, D.L., & Keating, M.T. (1995). LongQT syndrome associated with syndactyly identified in females.American Journal of Cardiology, 76(10),744-745.

Martin, A.B., & Kugler, J.D. (1999). Sinus node dysfunction.In P.C. Gillette & A.J. Garson (Eds.),Clinical Pediatric Ar-rhythmias(2nd ed., pp. 51-62). Philadelphia: W.B. SaundersCompany.

Panagiotopoulos, C., McCrindle, B.W., Hick, K., & Katz-man, D.K. (2000). Electrocardiographic findings in adolescentswith eating disorders.Pediatrics, 105(5),1100-1105.

Perry, J.C., & Garson, A.J. (1990). Supraventricular tachy-cardia due to Wolff-Parkinson-White syndrome in children:early disappearance and late recurrence.Journal of the Ameri-can of College Cardiology, 16(5),1215-1220.

Ross, B.A., & Gillette, P.C. (1999). Atrioventricular blockand bundle branch block. In P.C. Gillette & A.J. Garson (Eds.),Clinical Pediatric Arrhythmias(2nd ed., pp. 63-77). Philadel-phia: W.B. Saunders Company.

Schwartz, P.J., Priori, S.G., Locati, E.H., Napolitano, C.,Cantu, F., Towbin, J.A., Keating, M.T., Hammoude, H., Brown,A.M., Chen, L.-S.K., & Colatsky, T.J. (1995). Long QT syn-drome patient with mutations of the SCN5A and HERG genehave differential responses to Na1 channel blockade and toincreases in heart rate: Implications for gene-specific therapy.Circulation, 92(12),3381-3386.

Silka, M.J., & Garson, A.J. (1999). Ventricular arrhythmias.In P.C. Gillette & A.J. Garson (Eds.),Clinical Pediatric Ar-rhythmias(2nd ed., pp. 121-145). Philadelphia: W.B. SaundersCompany.


Sokoloski, M.C. (1999). Tachyarrhythmias confined to theatrium. In P.C. Gillette & A.J. Garson (Eds.),Clinical PediatricArrhythmias(2nd ed., pp. 78-96). Philadelphia: W.B. SaundersCompany.

Van Hare, G. (1999). Supraventricular tachycardia. In P.C.Gillette & A.J. Garson (Eds.),Clinical Pediatric Arrhythmias(2nd ed., pp. 97-120). Philadelphia: W.B. Saunders Company.

Waltuck, J., & Buyon, J. (1994). Autoantibody-associatedcongenital heart block: Outcome in mothers and children.An-nals of Internal Medicine, 120(7),544-551.

Zeigler, V.L., & Corbett, K.S. (1995). Psychosocial aspectsof caring for pediatric pacemaker recipients and their families.In P.C. Gillette & V.L. Zeigler (Eds.),Pediatric Cardiac Pac-ing (pp. 181-203). Armonk, NY: Futura Publishing.

362 DEBRA HANISCH

Documents

Pediatric arrhythmias.pdf