- Email: [email protected]
Detection of dangerous arrhythmias
OCCASIONAL REVIEW
Detection of dangerous arrhythmias
Fetal and early neonatal arrhythmias are discussed in more detail elsewhere and arrhythmias around the time of cardiac surgery are excluded.
J R Skinner
Classifying dangerous arrhythmias Arrhythmias can be dangerous when: 1. the heart rate is too fast or too slow to sustain cardiac output, 2. the arrhythmia is incessant and unrecognized, or 3. the arrhythmia is managed badly. Children with cardiac function already compromised due to heart disease are particularly vulnerable. The detection and prevention of dangerous arrhythmias relies on a high index of suspicion in the investigation of syncope, presyncope, seizure disorder, and heart failure. Palpitations are uncommonly the presenting feature of dangerous arrhythmias, unless associated with those other symptoms or signs. As paediatricians, we are more likely to prevent death due to arrhythmia by noting key features in the clinical history and family history, than by sophisticated interpretation of a rhythm strip or a 12-lead ECG, though the latter remain important. A willingness to consult early to get assistance with recognition and management of cases is also important.
Abstract This review focuses on arrhythmias in children and youth occurring in the community. Case examples with illustrative ECGs are presented, differentiation of cardiac from non-cardiac syncope is discussed, and examples of significant misdiagnosis and mismanagement are given. Aside from detection, there is also a focus on prevention, particularly through the recognition of inherited arrhythmic syndromes and through family screening. Key educational messages regarding syncope are the importance of detailed clinical history and of eliciting family history of sudden death, and the potential to misdiagnose arrhythmic syncope as epilepsy, particular when it occurs at night. Note is made that most community sudden death in children occurs at night or rest. In investigating dilated cardiomyopathy, incessant arrhythmias need to be excluded as a cause. Due to an incidence of sudden death in WolffeParkinsoneWhite syndrome (WPW), children with a delta wave on their ECGs after 4 years of age should see an electrophysiologist to assess risk of sudden death. Syncope with WPW requires immediate referral. To avoid causing iatrogenic harm in acute arrhythmia management, seek advice early and try to avoid the use of intravenous bolus doses of antiarrhythmic drugs with negative inotropic effect, particular verapamil, especially in infancy.
Teaching point: As paediatricians, we are more likely to prevent death due to arrhythmia by noting key features in the clinical history and family history, than by sophisticated interpretation of a rhythm strip or a 12-lead ECG.
Sudden cardiac death and inherited heart conditions Autopsy studies from NSW show that sudden cardiac death in 5e25-year olds occurs at approximately 3 per million per year. In 40% of these cases there were no findings on autopsy, suggesting a primary electrical disease (such as long QT syndrome) rather than a myopathic disease (such as hypertrophic cardiomyopathy) as the cause of death. In New Zealand over a 26-month period, coroner’s pathologists identified 17 1e24-year olds with a negative autopsy following a sudden unexpected death. This equates to approximately 2 per million per year. Thus, we expect more than 70 sudden cardiac deaths per year in Australia and New Zealand in this age group, about half of which are presumably due to a primary electrical disease.
Keywords Brugada syndrome; CPVT, catecholaminergic polymorphic ventricular tachycardia; long QT syndrome; seizure disorder; sudden cardiac death; SUDY, sudden unexplained death in the young; VT, ventricular tachycardia; WolfeParkinsoneWhite syndrome
Introduction Arrhythmias and the interpretation of ECGs form a small part of a paediatricians practice and it is hard to remain familiar with the nuances. Yet the stakes are high. Failure to recognize that a syncope, seizure or cardiac failure is secondary to a cardiac arrhythmia may result in inappropriate treatment a potentially preventable death. This review focuses on arrhythmias in children and youth occurring in the community and gives some take home lessons to help with clinical practice. Case examples with illustrative ECGs are presented, differentiation of cardiac from non-cardiac syncope is discussed, and examples of significant misdiagnosis and mismanagement are given. Aside from detection, there is also a focus on prevention, particularly through the recognition of inherited arrhythmic syndromes and through family screening.
Teaching point: More than 70 sudden cardiac deaths between age 1 and 24 years are expected per year in Australia and New Zealand.
Causes of post mortem-negative sudden unexpected death in the young (SUDY) Cardiac family studies and genetic tests in sudden unexplained (autopsy negative) death reveal that about 40% are due to inherited heart diseases. 15e20% are due to long QT syndrome, and the rest, in decreasing order, are due to catecholaminergic polymorphic ventricular tachycardia (CPVT), Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy (ARVC), and hypertrophic cardiomyopathy (HCM). ARVC and HCM can escape detection at autopsy, just as the subtle forms may be hard to diagnose in life (see Table 1).
J R Skinner MBChB DCH MRCP(UK) FRCPCH FRACP FCSANZ MD is in the Greenlane Paediatric and Congenital Cardiac Services at the Starship Children’s Hospital, Grafton, Auckland, New Zealand. Conflict of interest: none.
PAEDIATRICS AND CHILD HEALTH 21:8
369
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Inherited heart conditions commonly implicated in sudden arrhythmic death in 1e24-year olds
a
Inherited condition
Type
Typical trigger/s for syncope or sudden death
Diagnostic features
Approximate population prevalence
Long QT syndrome CPVT
With or after exertion, startle, nocturnal syncope/seizure, swimming Exercise or excitement, swimming. Fever, sleep/rest Exercise or excitement
HCM
Cardiomyopathy
Exercise
QTc interval >0.47 in females, >0.45 in males VT or ventricular ectopy on exercise testing “RBBB” appearance in V1 with ST elevation VT or ventricular ectopy on Holter, dilated RV with fatty infiltration on MRI etca Typical echocardiogram, ECG changes (septal Q waves, ST/T changes)
1 in 2500
Brugada syndrome ARVC
Cardiac ion channelopathy Cardiac ion channelopathy Cardiac ion channelopathy Cardiomyopathy
1 in 10,000 1 in 2000 1 in 5000
1 in 500
CPVT, catecholaminergic polymorphic ventricular tachycardia. ARVC, arrhythmogenic right ventricular cardiomyopathy, HCM, hypertrophic cardiomyopathy. ARVC is a clinical diagnosis based on meeting certain criteria (See Marcus et al 2010).
Table 1
The mechanism of sudden death in these inherited cardiac conditions is usually rapid polymorphic ventricular tachycardia (VT). Since prevention of these deaths is possible, usually with beta blockers or intracardiac defibrillators, there is much urgency to the identification of the arrhythmia not only in the patient, but also in family carriers of the abnormal gene. The conditions are generally monogenic and autosomal dominant, and one should expect to find an average of 8e9 gene carriers in extended families of each proband. Non-inherited arrhythmic causes of SUDY include Wolffe ParkinsoneWhite syndrome (WPW) and atrioventricular conduction block, both of which are difficult to diagnose with confidence on a standard autopsy.
misdiagnosed as a seizure disorder, the subject will receive the wrong treatment for many years, and may die as a result, as may other family members who remain undetected and unprotected. So what are the clinical features to help differentiate cardiac syncope from seizure disorders and vasovagal syncope?
Cardiac syncope vs. seizures and non-cardiac syncope
Detecting polymorphic VT in life
The classical arrhythmic syncope is sudden and unheralded, and may result in facial injury due to failure to protect themselves (unconscious before hitting the ground). Recovery is typically rapid. However, there are no good data from children to help us separate cardiac from non-cardiac syncope. A study of young adults (mean age around 40 years) by Colman et al compared features at presentation with syncope in a proven vasovagal group, a group presenting to an emergency department, and a group with proven long QT syndrome. Some features were significantly different between the groups. Those with long QT syndrome were more likely to have: 1. a positive family history for syncopal episodes, 2. a positive family for sudden death, 3. palpitations associated with the syncope. Triggers more likely to indicate long QT syndrome included 1. Syncope whilst supine (nocturnal seizures are very suspicious) 2. Emotion/loud noise or startle Features significantly associate with vasovagal syncope included nausea before the event, standing position, or syncope following venipuncture. However, none of these features taken alone separated the groups; even the best (family history of sudden death) was found in 17% of those with vasovagal syncope (compared to 66% with long QT). Strikingly there was no difference between the groups in the prevalence of sweating, abdominal pain, aura, chest pain, light headedness, paleness and blurring of vision.
As well as causing sudden death, self-limiting episodes of Polymorphic VT may produce repeated episodes of syncope, and hypoxaemic seizures may result. If the clinical episode is
Teaching point: Inherited arrhythmic syndromes, especially long QT syndrome, are commonly misdiagnosed as seizure disorder.
Teaching point: Most inherited heart conditions are generally monogenic and autosomal dominant, and one should expect to identify an average of 8e9 gene carriers in extended families of each proband.
Sudden death in young athletes Sudden death in athletes is caused primarily by structural heart disease, such as hypertrophic cardiomyopathy (36%), and coronary artery anomalies (17%). However, most children and youth dying suddenly in the community do so either at sleep/rest or during light activity, not during athletic activity, and among these the cardiac ion channelopathies predominate (long QT, CPVT, Brugada). Congenital heart diseases, such as aortic stenosis, and coronary anomalies and myocarditis appear in a minority in both groups. Teaching point: Most children and youth dying suddenly in the community do so either at sleep, rest or during light activity.
PAEDIATRICS AND CHILD HEALTH 21:8
370
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Consider particularly nocturnal seizures and those triggered by exercise or startle and with a normal EEG.
CPVT is as important as long QT syndrome as a cause of sudden death in children. It is the perfect occult killer; the resting ECG and echocardiogram are normal, and since more than half occur denovo in the individual, there is typically no family history to arouse suspicion. The diagnosis is made from the history of exercise or excitement-related dramatic syncope or near drowning. An exercise test reveals multiple ventricular ectopics, “bidirectional” or polymorphic ventricular tachycardia (Figure 1b). Most cases are due to mutations within the cardiac ryanodine gene (RyR2). An uncontrolled release of intracellular calcium results in premature ventricular depolarizations. CPVT is highly malignant and responds only partly to beta blockers. Effective treatment usually involves left cardiac sympathectomy, flecainide, and intracardiac cardioverter-defibrillators (ICDs). Figure 2 shows onset of torsade de points (TdP) in a patient with long QT syndrome. The accompanying ECG shows T wave alternans, often an immediate precursor to TdP. This girl is deaf and has Jervell and Lange-Nielsen syndrome, the most severe form of long QT syndrome. She presented as a newborn with bradycardia. Long QT syndrome is present on both sides of the family. Figure 3a shows an ECG taken from a 18-month-old child who presented with a fever and decreased conscious level e initially considered to be a febrile convulsion until the rapid heart rate was noticed. A broad complex tachycardia was seen but she coughed and went into sinus rhythm. Her resting ECG was
Interpreting the electrocardiogram Once suspicion is raised from the history, diagnosis is achieved by reliable interpretation of ECGs and the judicious use of ancillary tests e especially exercise testing, Holter recordings and event recorders.
How to measure a QT interval Measure the onset of the Q wave to the end of the T wave, as defined by the point where the steep down slope of the T wave crosses the baseline (“Teach the Tangent”). Divide by the square root of the preceding ReR interval to obtain the QTc (the heart rate correct QT interval). Measure a beat in lead II and lead V5, and report the longer of these two. In infancy, try to obtain an ECG with a heart rate less than 120 bpm. A QTc more than 0.45 s in males and 0.46 s in females is suspicious and requires expert review.
Arrhythmias which are too fast to sustain cardiac output Figure 1a shows a Polymorphic VT recorded during exercise related syncope on an implanted digital loop recorder in an 8-year-old. Figure 1b shows an exercise test in a child with the same condition e CPVT.
Figure 1 ECGs from an 8-year-old boy with CPVT (see text). a This event was recorded on an implanted digital loop recorder (“Reveal Plus”) device. Each marker indicates 1 s time interval. The boy lost consciousness. The small black triangle is where the device auto-activated to record the rhythm. In fact the asystole was detected by the device; the preceding rapid polymorphic VT had not been detected (it had been mistaken for electrical noise). Shortly afterwards he returns to sinus rhythm. b An exercise test in the same boy indicates normal QT interval, but there are multiple ventricular ectopics of bidirectional type (shown by the asterix), and a run of VT at the end of the screen (arrow).
PAEDIATRICS AND CHILD HEALTH 21:8
371
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 2 Long QT syndrome. a Torsade de pointes (TdP), another form of polymorphic VT, in a patient with long QT syndrome. The QT intervals are very long. Eventually one of the ventricular ectopics lands right on the peak of the broad T wave (arrow), and VT ensues. b 12-lead ECG showing gross QT prolongation (>700 ms). T wave alternans is visible on the lead II rhythm strip (arrowed, one T wave is down going, the next is up going). This commonly immediately precedes TdP.
abnormal (Figure 3a), revealing features of Brugada syndrome, best seen as a right bundle branch block-like pattern with ST elevation in leads V1eV3. Her mother’s ECG was normal at rest but became abnormal during a fever. Another example from an 8-month infant is shown in Figure 3b. Brugada syndrome is another cardiac ion channelopathy which in childhood typically presents with syncope, VT or sudden death triggered by fever. Management is with defibrillator pacemakers, and aggressive management of fevers. Figure 4a shows an ECG in a 14-year-old girl in a low output state after syncope playing sport. She was electrically cardioverted to sinus rhythm. She had a delta wave on her resting ECG. This was pre-excited atrial fibrillation. Patients with WPW (WolffeParkinsoneWhite) syndrome have an accessory pathway which can conduct forwards or backwards between the atrium and the ventricle. The fact that rapid atrial rates may be preferentially conducted down the pathway than the AV node is shown in Figure 4b. Common type “SVT” is rarely lifethreatening. However, WPW patients are at increased risk of atrial fibrillation, and about 25% of these pathways can conduct from the atrium to the ventricle at a rate so rapid it can be fatal. All children with a delta wave, symptomatic or not, persisting after the fourth year of life should be referred to a paediatric
PAEDIATRICS AND CHILD HEALTH 21:8
electrophysiologist to consider an electrophysiology study. This will define whether the pathway is potentially dangerous or not, and usually can be ablated at the same time. Teaching points: Due to an incidence of sudden death with WPW due to pre-excited atrial fibrillation, all children with a delta wave, symptomatic or not, persisting after the fourth year of life should be referred to a paediatric electrophysiologist to consider an electrophysiology study. Syncope with WPW requires immediate referral.
Arrhythmias where the heart rate is too slow to sustain cardiac output Death associated with bradycardia in children is usually secondary to respiratory or cerebral events, particularly in infancy. It is rare for primary bradycardia to be fatal otherwise in children. This may be because of the early neonatal or fetal detection of complete atrioventricular block, (Figure 5) and prophylactic pacing in those with very slow heart rates (<55 bpm). Beyond infancy, syncope with asystole or severe bradycardia is almost always neurocardiogenic. Severe reflex anoxic seizures are usually associated with asystole, but pacing is rarely required, though it is effective.
372
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 3 Brugada syndrome. a Resting ECG from an 18-month-old child presenting with VT during fever. b ECG from an 8-month infant with Brugada during fever. The features of Brugada syndrome are a right bundle branch block-like appearance with variable ST elevation in V1-V3.
Figure 4 WolffeParkinsoneWhite syndrome. a Pre-excited atrial fibrillation. This teenager presented in cardiovascular shock requiring DC cardioversion. The rhythm resembles polymorphic VT, although the upward slope at the start resembles a delta wave in several leads and it is more organized than polymorphic VT, but less regular than monomorphic VT. The diagnosis was confirmed when a delta wave was seen on the resting 12-lead ECG after cardioversion. b A rhythm strip here shows initially sinus rhythm, with a delta wave demonstrating some ventricular pre-excitation. At the first arrow, an atrial tachycardia starts up e the p wave is clearly different and the rate quicker, the subsequent three arrows indicate inverted p waves. After this the delta wave is more obvious, as the AV node no longer conducts, and conduction to the ventricle is preferentially via the accessory pathway (see text).
PAEDIATRICS AND CHILD HEALTH 21:8
373
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 5 Complete atrioventricular block. The arrows highlight the p waves, which are totally unrelated to the QRS complexes. This patient has a good junctional (narrow complex) escape rhythm, with a rate of over 80 beats per minute.
Incidental finding of second degree atrioventricular block may be important. Wenckebach block (Mobitz type 1 e progressive lengthening of the per interval prior to dropped QRS complex) is benign, related to vagal tone, and common during the night. However block of Mobitz type 2 can progress to complete block. The distinguishing feature is that there is a sudden atrioventricular block without the per interval lengthening before the blocked beat, or shortening after it. Referral for cardiological follow up is essential. Pacing for complete heart block is done for all patients beyond adolescence, because of a recognized risk of sudden death. Before then, most cardiologists will only recommend pacing for: 1. symptoms (syncope/presyncope/poor exercise tolerance), 2. sudden rate drops or pauses of greater than 3 s on serial Holters, 3. poor ventricular function on echocardiography, 4. broadening of the QRS width,
5. a long QT interval, 6. associated congenital heart disease.
Incessant tachyarrhythmias In the fetus, SVTs are a common cause of fetal hydrops. Most are accessory pathway mediated or atrial flutter. Beyond the newborn period, atrial ectopic tachycardia and PJRT (permanent junctional reciprocating tachycardia) are the two supraventricular tachycardias which most commonly cause a dilated cardiomyopathy. See Figure 6. They share three key features: 1. The p wave axis is abnormal, 2. The heart rate is only moderately fast but is incessant, or almost so (Heart rates of 140e160 bpm are typical in children or 180 bpm in the newborn.), 3. There is loss of the usual diurnal heart rate variation e the rate slows little at night.
Figure 6 “Long ReP tachycardia”. This infant presented with dilated cardiomyopathy. This rhythm was almost incessant. The p wave is inverted in leads II, III and aVF, indicating that the atrium is being depolarized in the wrong direction. The differential diagnosis includes atrial ectopic tachycardia and permanent junctional reciprocating tachycardia (PJRT), both of which are amenable to catheter ablation. (This one was PJRT).
PAEDIATRICS AND CHILD HEALTH 21:8
374
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 7 Fascicular (“verapamil sensitive”) VT (see text). This 8-month-old infant presented with shortness of breath and poor ventricular function. There is a right bundle branch block and left axis. The p waves are slower and dissociated from the ventricle (highlighted with arrows), confirming this is a VT; the tachycardia is independent of the atria. A capture beat is highlighted by the asterix, and yet the tachycardia continues. This proves that the AV node and His bundle are also independent of the tachycardia.
These tachycardias are gratifying to detect, because abolition of the tachycardia results in gradual resolution of the cardiomyopathy. Incessant ventricular tachycardia can also cause a dilated cardiomyopathy. Most monomorphic VTs in children are benign, in that they don’t degenerate into ventricular fibrillation and cause sudden death. However they can be relatively incessant, or there may be very frequent ventricular ectopy, between 10 and 70% of beats over 24 h. The commonest origin of these monomorphic ventricular beats is the right ventricular outflow tract; the ectopics have an inferior axis and left bundle branch blocklike appearance. The next commonest is a “verapamil sensitive” or fascicular VT, usually arising from the posterior fascicle in the left ventricle e see Figure 7. This more typically presents
like a paroxysmal SVT, but which doesn’t respond to adenosine or amiodarone. There is a right bundle branch block appearance, usually with a left axis. Both forms can be ablated with radiofrequency, or managed medically. For a summary of clinical presentations where arrhythmias should be considered see Table 2. Teaching point: Incessant tachycardia at relatively modest rates, or frequent ventricular ectopy, can cause a dilated cardiomyopathy.
Arrhythmias which are managed badly There have been many case reports of cardiovascular collapse and death after a rapid intravenous bolus of verapamil in infancy
Clinical presentations where cardiac arrhythmias should always be in the differential diagnosis
a
b
Presentation
Misdiagnoses
Potential causes
Investigations needed
Near drowning Seizures (typically nocturnal or post exercise, normal EEG) Syncope
Simple drowning Epilepsy, febrile convulsion Neurocardiogenic
Long QT, CPVT Long QT, Brugada, CPVT
ECG and exercise test, family investigation ECG, exercise test, family investigation
Long QT, CPVT, cardiomyopathy
Syncope/ sudden death with fever Syncope post exercise
Seizure disorder, septicaemia etc Neurocardiogenic
Brugada
History! (see text) Echocardiogram, ECG, exercise test, family investigation ECG during fever,a family investigation
Dilated cardiomyopathy
“Idiopathic”
Long QT syndrome, CPVT, ARVC, HCM Incessant arrhythmia such as ectopic atrial tachycardia
Echocardiogram,b ECG, exercise test, family investigation Careful review of ECG, Holter
The typical ECG changes of Brugada syndrome may be subtle or absent at rest but become manifest during fever, or by pharmacological challenge with a cardiac sodium channel blocker (such as flecainide or the shorter acting ajmaline). Echocardiography is unreliable to detect ARVC. Morphological features are rarely detected even by MRI in children under 13 years old. Cardiac MRI is used for screening children over 12.
Table 2
PAEDIATRICS AND CHILD HEALTH 21:8
375
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 8 A cardioversion from SVT going badly wrong. The defibrillator was not synchronizing properly with the R wave. A shock is delivered on the T wave and VF results. (The patient was cardioverted uneventfully back from VF to sinus rhythm with the next, non-synchronized, shock).
Summary
for SVT. In general avoid using any such negative inotrope intravenously (including propanolol or sotalol), especially in a subject with evidence of circulatory failure. Vagal manoeuvres or adenosine are nearly always enough to achieve initial cardioversion in the stable patient with SVT. If one has to use verapamil (such as one does with verapamil sensitive VT), give a slow infusion, over 20e30 min, in a high dependency environment, rather than a bolus. If adenosine works only transiently for SVT, then amiodarone is the drug of choice. Amiodarone has some negative inotropic effect, but given slowly this is minimal. The dose for SVT is 10e15 mcg/kg/min after a loading rate of 25 mcg/kg/min for the first 4 h in a high dependency environment. Do not give cardiac arrest sized bolus doses of amiodarone for SVT, this can cause cardiovascular collapse. Infants with SVT should be managed where respiratory support can be given quickly for the unexpected sudden deterioration. Do not use aggressive vagal manoeuvres (e.g. facial immersion) on an infant with circulatory failure or features of shock. Finally, always remember to set the cardioverter onto synchronous DC shock, and make sure it is detecting the R waves properly. Otherwise you may shock your patient into VF (Figure 8).
Since malignant arrhythmia in childhood usually occurs in inherited heart conditions, prevention depends on thorough family screening when a proband, either alive or deceased, is identified. Detection of dangerous arrhythmias requires a high index of suspicion when investigating seizures, especially when nocturnal or associated with exercise, and when investigating syncope, especially associated with water, exercise or startle. A 12-lead ECG alone is insufficient in investigation of suspicious syncope or seizure, and must be supplemented by an exercise test and an echocardiogram, thorough family history and often family investigation. All patients with a persistent delta wave beyond the age of 4 should be referred to an electrophysiologist for risk stratification.A
FURTHER READING 1 Skinner JR, Sharland G. Detection and management of life threatening arrhythmias in the perinatal period. Early Hum Dev 2008; 84: 161e72. 2 Doolan A, Langlois N, Semsarian C. Causes of sudden cardiac death in young Australians. Med J Aust 2004; 180: 110e2. 3 Skinner JR, Crawford J, Smith W, et al. Prospective, population-based long QT molecular autopsy study of postmortem negative sudden death in 1 to 40 year olds. Heart Rhythm; 8: 412e9. 4 Behr ER, Dalageorgou C, Christiansen M, et al. Sudden arrhythmic death syndrome: familial evaluation identifies inheritable heart disease in the majority of families. Eur Heart J 2008; 29: 1670e80. 5 Cerrone M, Napolitano C, Priori SG. Catecholaminergic polymorphic ventricular tachycardia: a paradigm to understand mechanisms of arrhythmias associated to impaired Ca(2þ) regulation. Heart Rhythm 2009; 6: 1652e9.
Teaching points: In SVT, try to avoid the use of intravenous negative inotropes such as verapamil, beta blockers, or bolus doses of amiodarone. For electrical cardioversion, take great care that the defibrillator has properly synchronized with the R wave.
Are some children at particular risk during SVT? Any child with compromised cardiac function may not tolerate even a simple SVT. Infants with single ventricle palliation, or children with cardiomyopathies are especially vulnerable. Seek advice early, intensive care support may be required.
PAEDIATRICS AND CHILD HEALTH 21:8
376
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
6 Probst V, Denjoy I, Meregalli PG, et al. Clinical aspects and prognosis of Brugada syndrome in children. Circulation 2007; 115: 2042e8. 7 Marcus FI, McKenna WJ, Sherrill D, et al. Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the task force criteria. Eur Heart J 2010; 31: 806e14. 8 Decker JA, Rossano JW, Smith EO, et al. Risk factors and mode of death in isolated hypertrophic cardiomyopathy in children. J Am Coll Cardiol 2009; 54: 250e4. 9 Goldenberg I, Moss AJ, Peterson DR, et al. Risk factors for aborted cardiac arrest and sudden cardiac death in children with the congenital long-QT syndrome. Circulation 2008; 117: 2184e91. 10 Maron BJ, Doerer JJ, Haas TS, Tierney DM, Mueller FO. Sudden deaths in young competitive athletes: analysis of 1866 deaths in the United States, 1980e2006. Circulation 2009; 119: 1085e92.
PAEDIATRICS AND CHILD HEALTH 21:8
11 MacCormick JM, McAlister H, Crawford J, et al. Misdiagnosis of long QT syndrome as epilepsy at first presentation. Ann Emerg Med 2009; 54: 26e32. 12 Colman N, Bakker A, Linzer M, Reitsma JB, Wieling W, Wilde AA. Value of history-taking in syncope patients: in whom to suspect long QT syndrome? Europace 2009; 11: 937e43. 13 Postema PG, De Jong JS, Van der Bilt IA, Wilde AA. Accurate electrocardiographic assessment of the QT interval: teach the tangent. Heart Rhythm 2008; 5: 1015e8. 14 Pfammatter JP, Paul T. Idiopathic ventricular tachycardia in infancy and childhood: a multicenter study on clinical profile and outcome. Working Group on Dysrhythmias and Electrophysiology of the Association for European Pediatric Cardiology. J Am Coll Cardiol 1999; 33: 2067e72.
377
Ó 2011 Elsevier Ltd. All rights reserved.
Detection of dangerous arrhythmias
Fetal and early neonatal arrhythmias are discussed in more detail elsewhere and arrhythmias around the time of cardiac surgery are excluded.
J R Skinner
Classifying dangerous arrhythmias Arrhythmias can be dangerous when: 1. the heart rate is too fast or too slow to sustain cardiac output, 2. the arrhythmia is incessant and unrecognized, or 3. the arrhythmia is managed badly. Children with cardiac function already compromised due to heart disease are particularly vulnerable. The detection and prevention of dangerous arrhythmias relies on a high index of suspicion in the investigation of syncope, presyncope, seizure disorder, and heart failure. Palpitations are uncommonly the presenting feature of dangerous arrhythmias, unless associated with those other symptoms or signs. As paediatricians, we are more likely to prevent death due to arrhythmia by noting key features in the clinical history and family history, than by sophisticated interpretation of a rhythm strip or a 12-lead ECG, though the latter remain important. A willingness to consult early to get assistance with recognition and management of cases is also important.
Abstract This review focuses on arrhythmias in children and youth occurring in the community. Case examples with illustrative ECGs are presented, differentiation of cardiac from non-cardiac syncope is discussed, and examples of significant misdiagnosis and mismanagement are given. Aside from detection, there is also a focus on prevention, particularly through the recognition of inherited arrhythmic syndromes and through family screening. Key educational messages regarding syncope are the importance of detailed clinical history and of eliciting family history of sudden death, and the potential to misdiagnose arrhythmic syncope as epilepsy, particular when it occurs at night. Note is made that most community sudden death in children occurs at night or rest. In investigating dilated cardiomyopathy, incessant arrhythmias need to be excluded as a cause. Due to an incidence of sudden death in WolffeParkinsoneWhite syndrome (WPW), children with a delta wave on their ECGs after 4 years of age should see an electrophysiologist to assess risk of sudden death. Syncope with WPW requires immediate referral. To avoid causing iatrogenic harm in acute arrhythmia management, seek advice early and try to avoid the use of intravenous bolus doses of antiarrhythmic drugs with negative inotropic effect, particular verapamil, especially in infancy.
Teaching point: As paediatricians, we are more likely to prevent death due to arrhythmia by noting key features in the clinical history and family history, than by sophisticated interpretation of a rhythm strip or a 12-lead ECG.
Sudden cardiac death and inherited heart conditions Autopsy studies from NSW show that sudden cardiac death in 5e25-year olds occurs at approximately 3 per million per year. In 40% of these cases there were no findings on autopsy, suggesting a primary electrical disease (such as long QT syndrome) rather than a myopathic disease (such as hypertrophic cardiomyopathy) as the cause of death. In New Zealand over a 26-month period, coroner’s pathologists identified 17 1e24-year olds with a negative autopsy following a sudden unexpected death. This equates to approximately 2 per million per year. Thus, we expect more than 70 sudden cardiac deaths per year in Australia and New Zealand in this age group, about half of which are presumably due to a primary electrical disease.
Keywords Brugada syndrome; CPVT, catecholaminergic polymorphic ventricular tachycardia; long QT syndrome; seizure disorder; sudden cardiac death; SUDY, sudden unexplained death in the young; VT, ventricular tachycardia; WolfeParkinsoneWhite syndrome
Introduction Arrhythmias and the interpretation of ECGs form a small part of a paediatricians practice and it is hard to remain familiar with the nuances. Yet the stakes are high. Failure to recognize that a syncope, seizure or cardiac failure is secondary to a cardiac arrhythmia may result in inappropriate treatment a potentially preventable death. This review focuses on arrhythmias in children and youth occurring in the community and gives some take home lessons to help with clinical practice. Case examples with illustrative ECGs are presented, differentiation of cardiac from non-cardiac syncope is discussed, and examples of significant misdiagnosis and mismanagement are given. Aside from detection, there is also a focus on prevention, particularly through the recognition of inherited arrhythmic syndromes and through family screening.
Teaching point: More than 70 sudden cardiac deaths between age 1 and 24 years are expected per year in Australia and New Zealand.
Causes of post mortem-negative sudden unexpected death in the young (SUDY) Cardiac family studies and genetic tests in sudden unexplained (autopsy negative) death reveal that about 40% are due to inherited heart diseases. 15e20% are due to long QT syndrome, and the rest, in decreasing order, are due to catecholaminergic polymorphic ventricular tachycardia (CPVT), Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy (ARVC), and hypertrophic cardiomyopathy (HCM). ARVC and HCM can escape detection at autopsy, just as the subtle forms may be hard to diagnose in life (see Table 1).
J R Skinner MBChB DCH MRCP(UK) FRCPCH FRACP FCSANZ MD is in the Greenlane Paediatric and Congenital Cardiac Services at the Starship Children’s Hospital, Grafton, Auckland, New Zealand. Conflict of interest: none.
PAEDIATRICS AND CHILD HEALTH 21:8
369
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Inherited heart conditions commonly implicated in sudden arrhythmic death in 1e24-year olds
a
Inherited condition
Type
Typical trigger/s for syncope or sudden death
Diagnostic features
Approximate population prevalence
Long QT syndrome CPVT
With or after exertion, startle, nocturnal syncope/seizure, swimming Exercise or excitement, swimming. Fever, sleep/rest Exercise or excitement
HCM
Cardiomyopathy
Exercise
QTc interval >0.47 in females, >0.45 in males VT or ventricular ectopy on exercise testing “RBBB” appearance in V1 with ST elevation VT or ventricular ectopy on Holter, dilated RV with fatty infiltration on MRI etca Typical echocardiogram, ECG changes (septal Q waves, ST/T changes)
1 in 2500
Brugada syndrome ARVC
Cardiac ion channelopathy Cardiac ion channelopathy Cardiac ion channelopathy Cardiomyopathy
1 in 10,000 1 in 2000 1 in 5000
1 in 500
CPVT, catecholaminergic polymorphic ventricular tachycardia. ARVC, arrhythmogenic right ventricular cardiomyopathy, HCM, hypertrophic cardiomyopathy. ARVC is a clinical diagnosis based on meeting certain criteria (See Marcus et al 2010).
Table 1
The mechanism of sudden death in these inherited cardiac conditions is usually rapid polymorphic ventricular tachycardia (VT). Since prevention of these deaths is possible, usually with beta blockers or intracardiac defibrillators, there is much urgency to the identification of the arrhythmia not only in the patient, but also in family carriers of the abnormal gene. The conditions are generally monogenic and autosomal dominant, and one should expect to find an average of 8e9 gene carriers in extended families of each proband. Non-inherited arrhythmic causes of SUDY include Wolffe ParkinsoneWhite syndrome (WPW) and atrioventricular conduction block, both of which are difficult to diagnose with confidence on a standard autopsy.
misdiagnosed as a seizure disorder, the subject will receive the wrong treatment for many years, and may die as a result, as may other family members who remain undetected and unprotected. So what are the clinical features to help differentiate cardiac syncope from seizure disorders and vasovagal syncope?
Cardiac syncope vs. seizures and non-cardiac syncope
Detecting polymorphic VT in life
The classical arrhythmic syncope is sudden and unheralded, and may result in facial injury due to failure to protect themselves (unconscious before hitting the ground). Recovery is typically rapid. However, there are no good data from children to help us separate cardiac from non-cardiac syncope. A study of young adults (mean age around 40 years) by Colman et al compared features at presentation with syncope in a proven vasovagal group, a group presenting to an emergency department, and a group with proven long QT syndrome. Some features were significantly different between the groups. Those with long QT syndrome were more likely to have: 1. a positive family history for syncopal episodes, 2. a positive family for sudden death, 3. palpitations associated with the syncope. Triggers more likely to indicate long QT syndrome included 1. Syncope whilst supine (nocturnal seizures are very suspicious) 2. Emotion/loud noise or startle Features significantly associate with vasovagal syncope included nausea before the event, standing position, or syncope following venipuncture. However, none of these features taken alone separated the groups; even the best (family history of sudden death) was found in 17% of those with vasovagal syncope (compared to 66% with long QT). Strikingly there was no difference between the groups in the prevalence of sweating, abdominal pain, aura, chest pain, light headedness, paleness and blurring of vision.
As well as causing sudden death, self-limiting episodes of Polymorphic VT may produce repeated episodes of syncope, and hypoxaemic seizures may result. If the clinical episode is
Teaching point: Inherited arrhythmic syndromes, especially long QT syndrome, are commonly misdiagnosed as seizure disorder.
Teaching point: Most inherited heart conditions are generally monogenic and autosomal dominant, and one should expect to identify an average of 8e9 gene carriers in extended families of each proband.
Sudden death in young athletes Sudden death in athletes is caused primarily by structural heart disease, such as hypertrophic cardiomyopathy (36%), and coronary artery anomalies (17%). However, most children and youth dying suddenly in the community do so either at sleep/rest or during light activity, not during athletic activity, and among these the cardiac ion channelopathies predominate (long QT, CPVT, Brugada). Congenital heart diseases, such as aortic stenosis, and coronary anomalies and myocarditis appear in a minority in both groups. Teaching point: Most children and youth dying suddenly in the community do so either at sleep, rest or during light activity.
PAEDIATRICS AND CHILD HEALTH 21:8
370
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Consider particularly nocturnal seizures and those triggered by exercise or startle and with a normal EEG.
CPVT is as important as long QT syndrome as a cause of sudden death in children. It is the perfect occult killer; the resting ECG and echocardiogram are normal, and since more than half occur denovo in the individual, there is typically no family history to arouse suspicion. The diagnosis is made from the history of exercise or excitement-related dramatic syncope or near drowning. An exercise test reveals multiple ventricular ectopics, “bidirectional” or polymorphic ventricular tachycardia (Figure 1b). Most cases are due to mutations within the cardiac ryanodine gene (RyR2). An uncontrolled release of intracellular calcium results in premature ventricular depolarizations. CPVT is highly malignant and responds only partly to beta blockers. Effective treatment usually involves left cardiac sympathectomy, flecainide, and intracardiac cardioverter-defibrillators (ICDs). Figure 2 shows onset of torsade de points (TdP) in a patient with long QT syndrome. The accompanying ECG shows T wave alternans, often an immediate precursor to TdP. This girl is deaf and has Jervell and Lange-Nielsen syndrome, the most severe form of long QT syndrome. She presented as a newborn with bradycardia. Long QT syndrome is present on both sides of the family. Figure 3a shows an ECG taken from a 18-month-old child who presented with a fever and decreased conscious level e initially considered to be a febrile convulsion until the rapid heart rate was noticed. A broad complex tachycardia was seen but she coughed and went into sinus rhythm. Her resting ECG was
Interpreting the electrocardiogram Once suspicion is raised from the history, diagnosis is achieved by reliable interpretation of ECGs and the judicious use of ancillary tests e especially exercise testing, Holter recordings and event recorders.
How to measure a QT interval Measure the onset of the Q wave to the end of the T wave, as defined by the point where the steep down slope of the T wave crosses the baseline (“Teach the Tangent”). Divide by the square root of the preceding ReR interval to obtain the QTc (the heart rate correct QT interval). Measure a beat in lead II and lead V5, and report the longer of these two. In infancy, try to obtain an ECG with a heart rate less than 120 bpm. A QTc more than 0.45 s in males and 0.46 s in females is suspicious and requires expert review.
Arrhythmias which are too fast to sustain cardiac output Figure 1a shows a Polymorphic VT recorded during exercise related syncope on an implanted digital loop recorder in an 8-year-old. Figure 1b shows an exercise test in a child with the same condition e CPVT.
Figure 1 ECGs from an 8-year-old boy with CPVT (see text). a This event was recorded on an implanted digital loop recorder (“Reveal Plus”) device. Each marker indicates 1 s time interval. The boy lost consciousness. The small black triangle is where the device auto-activated to record the rhythm. In fact the asystole was detected by the device; the preceding rapid polymorphic VT had not been detected (it had been mistaken for electrical noise). Shortly afterwards he returns to sinus rhythm. b An exercise test in the same boy indicates normal QT interval, but there are multiple ventricular ectopics of bidirectional type (shown by the asterix), and a run of VT at the end of the screen (arrow).
PAEDIATRICS AND CHILD HEALTH 21:8
371
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 2 Long QT syndrome. a Torsade de pointes (TdP), another form of polymorphic VT, in a patient with long QT syndrome. The QT intervals are very long. Eventually one of the ventricular ectopics lands right on the peak of the broad T wave (arrow), and VT ensues. b 12-lead ECG showing gross QT prolongation (>700 ms). T wave alternans is visible on the lead II rhythm strip (arrowed, one T wave is down going, the next is up going). This commonly immediately precedes TdP.
abnormal (Figure 3a), revealing features of Brugada syndrome, best seen as a right bundle branch block-like pattern with ST elevation in leads V1eV3. Her mother’s ECG was normal at rest but became abnormal during a fever. Another example from an 8-month infant is shown in Figure 3b. Brugada syndrome is another cardiac ion channelopathy which in childhood typically presents with syncope, VT or sudden death triggered by fever. Management is with defibrillator pacemakers, and aggressive management of fevers. Figure 4a shows an ECG in a 14-year-old girl in a low output state after syncope playing sport. She was electrically cardioverted to sinus rhythm. She had a delta wave on her resting ECG. This was pre-excited atrial fibrillation. Patients with WPW (WolffeParkinsoneWhite) syndrome have an accessory pathway which can conduct forwards or backwards between the atrium and the ventricle. The fact that rapid atrial rates may be preferentially conducted down the pathway than the AV node is shown in Figure 4b. Common type “SVT” is rarely lifethreatening. However, WPW patients are at increased risk of atrial fibrillation, and about 25% of these pathways can conduct from the atrium to the ventricle at a rate so rapid it can be fatal. All children with a delta wave, symptomatic or not, persisting after the fourth year of life should be referred to a paediatric
PAEDIATRICS AND CHILD HEALTH 21:8
electrophysiologist to consider an electrophysiology study. This will define whether the pathway is potentially dangerous or not, and usually can be ablated at the same time. Teaching points: Due to an incidence of sudden death with WPW due to pre-excited atrial fibrillation, all children with a delta wave, symptomatic or not, persisting after the fourth year of life should be referred to a paediatric electrophysiologist to consider an electrophysiology study. Syncope with WPW requires immediate referral.
Arrhythmias where the heart rate is too slow to sustain cardiac output Death associated with bradycardia in children is usually secondary to respiratory or cerebral events, particularly in infancy. It is rare for primary bradycardia to be fatal otherwise in children. This may be because of the early neonatal or fetal detection of complete atrioventricular block, (Figure 5) and prophylactic pacing in those with very slow heart rates (<55 bpm). Beyond infancy, syncope with asystole or severe bradycardia is almost always neurocardiogenic. Severe reflex anoxic seizures are usually associated with asystole, but pacing is rarely required, though it is effective.
372
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 3 Brugada syndrome. a Resting ECG from an 18-month-old child presenting with VT during fever. b ECG from an 8-month infant with Brugada during fever. The features of Brugada syndrome are a right bundle branch block-like appearance with variable ST elevation in V1-V3.
Figure 4 WolffeParkinsoneWhite syndrome. a Pre-excited atrial fibrillation. This teenager presented in cardiovascular shock requiring DC cardioversion. The rhythm resembles polymorphic VT, although the upward slope at the start resembles a delta wave in several leads and it is more organized than polymorphic VT, but less regular than monomorphic VT. The diagnosis was confirmed when a delta wave was seen on the resting 12-lead ECG after cardioversion. b A rhythm strip here shows initially sinus rhythm, with a delta wave demonstrating some ventricular pre-excitation. At the first arrow, an atrial tachycardia starts up e the p wave is clearly different and the rate quicker, the subsequent three arrows indicate inverted p waves. After this the delta wave is more obvious, as the AV node no longer conducts, and conduction to the ventricle is preferentially via the accessory pathway (see text).
PAEDIATRICS AND CHILD HEALTH 21:8
373
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 5 Complete atrioventricular block. The arrows highlight the p waves, which are totally unrelated to the QRS complexes. This patient has a good junctional (narrow complex) escape rhythm, with a rate of over 80 beats per minute.
Incidental finding of second degree atrioventricular block may be important. Wenckebach block (Mobitz type 1 e progressive lengthening of the per interval prior to dropped QRS complex) is benign, related to vagal tone, and common during the night. However block of Mobitz type 2 can progress to complete block. The distinguishing feature is that there is a sudden atrioventricular block without the per interval lengthening before the blocked beat, or shortening after it. Referral for cardiological follow up is essential. Pacing for complete heart block is done for all patients beyond adolescence, because of a recognized risk of sudden death. Before then, most cardiologists will only recommend pacing for: 1. symptoms (syncope/presyncope/poor exercise tolerance), 2. sudden rate drops or pauses of greater than 3 s on serial Holters, 3. poor ventricular function on echocardiography, 4. broadening of the QRS width,
5. a long QT interval, 6. associated congenital heart disease.
Incessant tachyarrhythmias In the fetus, SVTs are a common cause of fetal hydrops. Most are accessory pathway mediated or atrial flutter. Beyond the newborn period, atrial ectopic tachycardia and PJRT (permanent junctional reciprocating tachycardia) are the two supraventricular tachycardias which most commonly cause a dilated cardiomyopathy. See Figure 6. They share three key features: 1. The p wave axis is abnormal, 2. The heart rate is only moderately fast but is incessant, or almost so (Heart rates of 140e160 bpm are typical in children or 180 bpm in the newborn.), 3. There is loss of the usual diurnal heart rate variation e the rate slows little at night.
Figure 6 “Long ReP tachycardia”. This infant presented with dilated cardiomyopathy. This rhythm was almost incessant. The p wave is inverted in leads II, III and aVF, indicating that the atrium is being depolarized in the wrong direction. The differential diagnosis includes atrial ectopic tachycardia and permanent junctional reciprocating tachycardia (PJRT), both of which are amenable to catheter ablation. (This one was PJRT).
PAEDIATRICS AND CHILD HEALTH 21:8
374
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 7 Fascicular (“verapamil sensitive”) VT (see text). This 8-month-old infant presented with shortness of breath and poor ventricular function. There is a right bundle branch block and left axis. The p waves are slower and dissociated from the ventricle (highlighted with arrows), confirming this is a VT; the tachycardia is independent of the atria. A capture beat is highlighted by the asterix, and yet the tachycardia continues. This proves that the AV node and His bundle are also independent of the tachycardia.
These tachycardias are gratifying to detect, because abolition of the tachycardia results in gradual resolution of the cardiomyopathy. Incessant ventricular tachycardia can also cause a dilated cardiomyopathy. Most monomorphic VTs in children are benign, in that they don’t degenerate into ventricular fibrillation and cause sudden death. However they can be relatively incessant, or there may be very frequent ventricular ectopy, between 10 and 70% of beats over 24 h. The commonest origin of these monomorphic ventricular beats is the right ventricular outflow tract; the ectopics have an inferior axis and left bundle branch blocklike appearance. The next commonest is a “verapamil sensitive” or fascicular VT, usually arising from the posterior fascicle in the left ventricle e see Figure 7. This more typically presents
like a paroxysmal SVT, but which doesn’t respond to adenosine or amiodarone. There is a right bundle branch block appearance, usually with a left axis. Both forms can be ablated with radiofrequency, or managed medically. For a summary of clinical presentations where arrhythmias should be considered see Table 2. Teaching point: Incessant tachycardia at relatively modest rates, or frequent ventricular ectopy, can cause a dilated cardiomyopathy.
Arrhythmias which are managed badly There have been many case reports of cardiovascular collapse and death after a rapid intravenous bolus of verapamil in infancy
Clinical presentations where cardiac arrhythmias should always be in the differential diagnosis
a
b
Presentation
Misdiagnoses
Potential causes
Investigations needed
Near drowning Seizures (typically nocturnal or post exercise, normal EEG) Syncope
Simple drowning Epilepsy, febrile convulsion Neurocardiogenic
Long QT, CPVT Long QT, Brugada, CPVT
ECG and exercise test, family investigation ECG, exercise test, family investigation
Long QT, CPVT, cardiomyopathy
Syncope/ sudden death with fever Syncope post exercise
Seizure disorder, septicaemia etc Neurocardiogenic
Brugada
History! (see text) Echocardiogram, ECG, exercise test, family investigation ECG during fever,a family investigation
Dilated cardiomyopathy
“Idiopathic”
Long QT syndrome, CPVT, ARVC, HCM Incessant arrhythmia such as ectopic atrial tachycardia
Echocardiogram,b ECG, exercise test, family investigation Careful review of ECG, Holter
The typical ECG changes of Brugada syndrome may be subtle or absent at rest but become manifest during fever, or by pharmacological challenge with a cardiac sodium channel blocker (such as flecainide or the shorter acting ajmaline). Echocardiography is unreliable to detect ARVC. Morphological features are rarely detected even by MRI in children under 13 years old. Cardiac MRI is used for screening children over 12.
Table 2
PAEDIATRICS AND CHILD HEALTH 21:8
375
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
Figure 8 A cardioversion from SVT going badly wrong. The defibrillator was not synchronizing properly with the R wave. A shock is delivered on the T wave and VF results. (The patient was cardioverted uneventfully back from VF to sinus rhythm with the next, non-synchronized, shock).
Summary
for SVT. In general avoid using any such negative inotrope intravenously (including propanolol or sotalol), especially in a subject with evidence of circulatory failure. Vagal manoeuvres or adenosine are nearly always enough to achieve initial cardioversion in the stable patient with SVT. If one has to use verapamil (such as one does with verapamil sensitive VT), give a slow infusion, over 20e30 min, in a high dependency environment, rather than a bolus. If adenosine works only transiently for SVT, then amiodarone is the drug of choice. Amiodarone has some negative inotropic effect, but given slowly this is minimal. The dose for SVT is 10e15 mcg/kg/min after a loading rate of 25 mcg/kg/min for the first 4 h in a high dependency environment. Do not give cardiac arrest sized bolus doses of amiodarone for SVT, this can cause cardiovascular collapse. Infants with SVT should be managed where respiratory support can be given quickly for the unexpected sudden deterioration. Do not use aggressive vagal manoeuvres (e.g. facial immersion) on an infant with circulatory failure or features of shock. Finally, always remember to set the cardioverter onto synchronous DC shock, and make sure it is detecting the R waves properly. Otherwise you may shock your patient into VF (Figure 8).
Since malignant arrhythmia in childhood usually occurs in inherited heart conditions, prevention depends on thorough family screening when a proband, either alive or deceased, is identified. Detection of dangerous arrhythmias requires a high index of suspicion when investigating seizures, especially when nocturnal or associated with exercise, and when investigating syncope, especially associated with water, exercise or startle. A 12-lead ECG alone is insufficient in investigation of suspicious syncope or seizure, and must be supplemented by an exercise test and an echocardiogram, thorough family history and often family investigation. All patients with a persistent delta wave beyond the age of 4 should be referred to an electrophysiologist for risk stratification.A
FURTHER READING 1 Skinner JR, Sharland G. Detection and management of life threatening arrhythmias in the perinatal period. Early Hum Dev 2008; 84: 161e72. 2 Doolan A, Langlois N, Semsarian C. Causes of sudden cardiac death in young Australians. Med J Aust 2004; 180: 110e2. 3 Skinner JR, Crawford J, Smith W, et al. Prospective, population-based long QT molecular autopsy study of postmortem negative sudden death in 1 to 40 year olds. Heart Rhythm; 8: 412e9. 4 Behr ER, Dalageorgou C, Christiansen M, et al. Sudden arrhythmic death syndrome: familial evaluation identifies inheritable heart disease in the majority of families. Eur Heart J 2008; 29: 1670e80. 5 Cerrone M, Napolitano C, Priori SG. Catecholaminergic polymorphic ventricular tachycardia: a paradigm to understand mechanisms of arrhythmias associated to impaired Ca(2þ) regulation. Heart Rhythm 2009; 6: 1652e9.
Teaching points: In SVT, try to avoid the use of intravenous negative inotropes such as verapamil, beta blockers, or bolus doses of amiodarone. For electrical cardioversion, take great care that the defibrillator has properly synchronized with the R wave.
Are some children at particular risk during SVT? Any child with compromised cardiac function may not tolerate even a simple SVT. Infants with single ventricle palliation, or children with cardiomyopathies are especially vulnerable. Seek advice early, intensive care support may be required.
PAEDIATRICS AND CHILD HEALTH 21:8
376
Ó 2011 Elsevier Ltd. All rights reserved.
OCCASIONAL REVIEW
6 Probst V, Denjoy I, Meregalli PG, et al. Clinical aspects and prognosis of Brugada syndrome in children. Circulation 2007; 115: 2042e8. 7 Marcus FI, McKenna WJ, Sherrill D, et al. Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the task force criteria. Eur Heart J 2010; 31: 806e14. 8 Decker JA, Rossano JW, Smith EO, et al. Risk factors and mode of death in isolated hypertrophic cardiomyopathy in children. J Am Coll Cardiol 2009; 54: 250e4. 9 Goldenberg I, Moss AJ, Peterson DR, et al. Risk factors for aborted cardiac arrest and sudden cardiac death in children with the congenital long-QT syndrome. Circulation 2008; 117: 2184e91. 10 Maron BJ, Doerer JJ, Haas TS, Tierney DM, Mueller FO. Sudden deaths in young competitive athletes: analysis of 1866 deaths in the United States, 1980e2006. Circulation 2009; 119: 1085e92.
PAEDIATRICS AND CHILD HEALTH 21:8
11 MacCormick JM, McAlister H, Crawford J, et al. Misdiagnosis of long QT syndrome as epilepsy at first presentation. Ann Emerg Med 2009; 54: 26e32. 12 Colman N, Bakker A, Linzer M, Reitsma JB, Wieling W, Wilde AA. Value of history-taking in syncope patients: in whom to suspect long QT syndrome? Europace 2009; 11: 937e43. 13 Postema PG, De Jong JS, Van der Bilt IA, Wilde AA. Accurate electrocardiographic assessment of the QT interval: teach the tangent. Heart Rhythm 2008; 5: 1015e8. 14 Pfammatter JP, Paul T. Idiopathic ventricular tachycardia in infancy and childhood: a multicenter study on clinical profile and outcome. Working Group on Dysrhythmias and Electrophysiology of the Association for European Pediatric Cardiology. J Am Coll Cardiol 1999; 33: 2067e72.
377
Ó 2011 Elsevier Ltd. All rights reserved.