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Arrhythmias in Children: Assessment and Management Robert H. Pass, MD Director, Pediatric Cardiac Electrophysiology Montefiore Medical Center – Albert Einstein College of Medicine Pediatric Arrhythmia Management • Bradycardia (“Boring”) vs. • Tachycardias (“Exciting”) Disorders of Automaticity Disorders of Reentry Pediatric Arrhythmia Management • Normal Cardiac Conduction System – Electrical Anatomic Substrate Bradyarrhythmias • Sinus Node Dysfunction: – Rare in patients with structurally normal hearts – Commonly seen following palliative congenital heart surgery: • Acutely: – AV Canal Repairs – Sinus Venosus ASD repair • Chronically: – Mustard/Senning Repair of DTGA – Fontan Palliation of Single Ventricular hearts Bradyarrhythmias Mustard Procedure for D-Transposition of the Great Arteries Bradyarrhythmias • 75% of all DTGA patients undergoing Mustard at Columbia not in sinus rhythm at follow-up Bradyarrhthmias • Conduction Block ________ ______________ _________ _______________ ______________ Bradyarrhythmias • Causes of Block: Infectious: Inflammatory: Trauma: Neurodegenerative: Infiltrative disorders: Pharmacologic: Viral myocarditis Lyme Disease Chagas Disease Rheumatoid arthritis Cardiac Surgery Radiation therapy Myotonic dystrophy Kearns-Sayre syndrome Tuberous Sclerosis Amyloidosis Tricyclic antidepressants Digoxin Diptheria Endocarditis Guillain-Barre Blunt chest trauma Muscular dystrophy Lymphoma Sarcoid Antiarrhythmic agents Clonidine Bradyarrhythmias • Clinical Examples 7 year old with history of severe cold symptoms, lethargy, dyspnea and echocardiogram demonstrated severe ventricular dysfunction Bradyarrhythmias • Clinical Examples 8 year old referred to cardiology for evaluation of heart murmur Bradyarrhythmias • Treatment: - Treat underlying problem - If postoperative CHB or due to irreversible cause, pacemaker implantation Bradyarrhythmias 9 Months old • 30 Months old Transvenous Pacemaker in Infant – “Loop” technique (from Spotnitz et al. Annals of Thoracic Surgery , 1991) Tachyarrhythmias • Disorders of Automaticity VS. • Disorders of Reentry Tachyarrhythmias - Automatic • Common characteristics of automatic arrhythmias include: - “heat up” / “cool down” - No abrupt onset or offset - Cannot be DC cardioverted - Very catecholamine sensitive Tachyarrhythmias - Automatic • Clinical Examples of Automatic Tachyarrhythmias: - Sinus tachycardia - Ectopic atrial tachycardia (EAT) - Junctional Ectopic Tachycardia (JET) - Some types of VT Tachyarrhythmias • Disorders of automaticity: “Whatever is fastest in the heart wins’” • In automatic arrhythmias, an area of myocardium with calcium channel cells fires at a rate that is faster than the sinus node and therefore controls the rhythm Tachyarrhythmias - Automatic • Clinical Example: 14 year old girl seen by pediatrician who heard irregular heart beat and obtained ECG; recent history of fainting without palpitations; Echocardiogram demonstrated severely depressed function Tachyarrhythmias - Automatic • EAT – Ectopic Atrial Tachycardia • Atrial ectopy from a single area of atrial myocardium other than sinus node • Commonly results in ventricular dysfunction Tachyarrhythmias - Automatic • Clinical Example 5 mo s/p Tetralogy of Fallot repair – postoperative hour 4 JET !!!!!!! Tachyarrhythmias - Automatic • Clinical Example: 15 year old with history of VT – noncompliant with medication ER 1999 Tachyarrhythmias - Reentry • Reentry • 1. 2. 3. - represents 90% of SVT in pediatric populations 3 Major Requirements: 2 pathways connected proximally and distally Unidirectional block in one pathway A zone of slow conduction Tachyarrhythmias - Reentry • Reentry General Characteristics: 1. Rhythm can be initiated and terminated with appropriately timed premature beats. 2. Abrupt onset and termination. 3. Successful termination (at least temporarily) with DC cardioversion Tachyarrhythmias - Reentry • Reentry Clinical examples of reentry include: - Accessory pathway (“bypass tract”) mediated tachycardia (e.g. WPW) - AV nodal reentry (AVNRT) - Atrial Flutter - Some ventricular tachycardias Tachyarrhythmias - Reentry • Accessory pathway tachycardia is most common etiology of tachycardia in children • More common in males • Typical route is from atria to ventricles via AV node and retrograde via accessory pathway – Orthodromic Reentrant Tachycardia (ORT) Tachyarrhythmias - Reentry • Clinical example : 15 year old boy with history of Ebstein’s anomaly and intermittent palpitations Tachycardia Sinus Rhythm Tachyarrhythmias - Reentry • Peak age for occurrence of SVT/ORT is first 2 months of age – 40% of first episodes occur this early in life • Frequency decreases over first year of life – 2/3 of infants no longer have clinical tachycardia at age 1 year and 1/3 have no evidence of accessory pathway conduction at one year by formal transesophageal testing Tachyarrhythmias - Reentry • Other peaks for tachycardia recurrence are 5-8 years and 10-15 years • ~ 40% of patients with tachycardia as young infants will recur some time in life • Reasons for this finding unclear Tachyarrhythmias - Reentry • WPW – Paradigm of ORT • First described in 1930 • Short PR interval, bundle branch block on resting surface ECG and intermittent tachycardia • Presence of delta wave – ventricular preexcitation • Risk of sudden death ~ 1.5/1000 pt. years Tachyarrhythmias - Reentry • Clinical example: 15 year old boy with insignificant past medical history seen in ER with palpitations and dizziness Tachyarrythmias - Reentry Acute therapy was administered: Tachyarrhythmias - Reentry • ECG s/p DC Cardioversion • Wolff Parkinson White Syndrome! Tachyarrhythmias - WPW • Mechanism of arrhythmia is preexcited atrial fibrillation • Most common cause of sudden death in WPW Tachyarrhythmias - WPW • WPW – Key points: 1. Risk of death is not from SVT/ORT but instead from rapidly conducted A fib (rare in infants). 2. Digoxin/Verapamil are contraindicated in older patients. 3. Parent education about identifying tachycardia critical. Tachyarrhythmias - Reentry • 16 year old with palpitations and dizziness 10 years s/p Fontan palliation for tricuspid atresia Tachyarrhythmias - Reentry • Intraatrial Reentrant Tachycardia (IART): - Common problem affecting 12.5-26% of patients with repaired/palliated CHD at intermediate and long-term follow-up - Particular problem among Fontan patients Tachyarrhythmias - Reentry • IART is virtually universal following Fontan (from Fishberger et al. JTCVS, 1997) Tachyarrhythmias - Reentry • Typical IART reentrant loop due to scarring in postoperative children Tachyarrhythmias – Summary of Mechanisms Level of Heart Automaticity Reentry SA Node Sinus tachycardia SA node reentry Atrial muscle EAT/MAT Aflutter/Afib AV Node JET AVNRT AV reciprocating NA WPW/ Concealed AP Ventricles VT VT/VF Tachyarrhythmias - Treatment • Chronic/”Definitive” therapy: Drug therapy – in general, for most forms of SVT, drugs are effective Most commonly used agents: Digoxin Sotalol Procainamide Amiodarone Betablockers Flecainide Verapamil Tachyarrhythmias – Drug Therapy • Acute therapy: – IV adenosine – causes transient AV nodal blockade • Particularly useful for AV reciprocating tachycardias such as ORT or AVNRT (2 most common SVT’s in children) – IV verapamil – also causes AV nodal blockade • Not as commonly used due to potent negative inotropy – also shown to be associated with cardiovascular collapse in infants Tachyarrhythmias – Drug Therapy • Chronic Therapy: (Infancy) – Digoxin • Useful antiarrhythmic agent in infants • Causes AV nodal slowing and reduces atrial ectopy • Dosing from 8-14 mcg/kg/day divided bid – Beta Blockers • • • • Useful alternative antiarrhythmic agent in infants Causes AV nodal slowing and reduces atrial ectopy Commonly used agent is Inderal Associated with low blood glucose levels – “D sticks” must be monitored initially Arrhythmias – Drug Therapy • Chronic Therapy – Children and Adolescents: – Beta blockade – effective about 60-75% • Low side effect profile – Calcium channel blockers – similar efficacy • Low side effect profile (e.g. Verapamil) – Digoxin – not as effective in older patients as in infancy and thus not typically used in this age range Arrhythmias – Drug Therapy • Chronic Therapy – When the “SIMPLE STUFF” doesn’t work: – Sotalol • • • • Class III agent Potent beta blocker High incidence of proarrhythmia (~ 10%) Significantly more effective than “simple” agents – Flecainide • Class Ib agent • Very effective • ? High incidence of proarrhythmia (CAST study) Arrhythmias – Drug Therapy • Amiodarone – Class III agent (“all 4 Vaughn Williams classification effects”) – Very effective agent – Very long half life (~ 45 days) – Low incidence of proarrhythmia – High side effect profile • Pulmonary Liver Thyroid • Eye GI tract Skin Tachyarrhythmias - Therapy • Drugs are not a “free ride” - Side effects (cardiac and non-cardiac) - Proarrhythmia - Not always efficacious - Compliance -? Lifelong usage - For WPW, may not reduce risk of sudden death Tachyarrhythmias - Therapy • Drug therapy for IART “stinks” -% freedom from recurrence of IART on various antiarrhythmic agents in patients s/p CHD surgery from Weindling et al. – Unpublished abstract Tachyarrhythmias - Therapy • Radiofrequency Catheter Ablation (RFCA) • Advantages: Potentially “Definitive” therapy Drug use often not required following procedure Tachyarrhythmias - Therapy • RFCA technical considerations • Minimum of 4-5 catheters • 2-3 cardiologists • 1 nurse/1 CV tech • Computerized on-line analysis • Fluoroscopy • Programmable stimulator Tachyarrhythmias - Therapy • Simplified example of successful ablation of left sided EAT focus in 5 year old Tachyarrhythmias - Therapy •RFCA Success Rates are quite high ! (Boston Children’s Data – J Peds 1997) •Data from Children’s Hospital at Montefiore for past 3 years – overall success rate ~ 94% Diagnosis Success (%) WPW Concealed AP PJRT EAT Mahaim AVNRT Totals 94 99 95 100 100 83 90 Tachyarrhythmias - Therapy • Risks associated with RFCA: – Normal cath risks: bleeding, stroke, infection – Serious complications (death, ventricular dysfunction, CVA, cardiac perforation) • Occurred 1.2% of time in Tanel, Boston Children’s Study (1997) Tachyarrhythmias - Therapy • Angiogram of Fontan – GIGANTIC RA – “so much ground to cover” Tachyarrhythmias - Therapy • Data for standard RFCA of IART have been generally poor using standard techniques • ~ 50% arrhythmia free at 2 years follow-up • In light of these findings, interest in newer mapping techniques are growing Tachyarrhythmias - Therapy Newer Mapping Strategies Carto – Biosense Electroanatomical Mapping System Tachyarrhythmias – New Mapping Strategies • Electroanatomical Mapping – Non Contact – Endocardial Solutions 9 French Balloon Catheter Tachyarrhythmias – Newer Therapies • Newer “Chilli” catheters – allowing larger and deeper radiofrequency lesions for IART in Fontan patients Cryoablation – Smaller “reversible” lesions Tachyarrhythmias – New Directions • Refining of newer mapping strategies for better understanding of scar anatomy and its relationship to IART • Newer surgical approaches to congenital surgery to reduce rates of IART or to treat it (cryosurgery) • New catheter design to lower cath-related risks of RFCA (e.g. Cryocatheters) • Use of low fluoroscopy protocols and 3 D electroanatomical mapping techniques to reduce exposure to ionizing radiation