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: Viral myocarditisDiptheria Lyme DiseaseEndocarditis Chagas Disease Inflammatory: Rheumatoid arthritisGuillain-Barre Trauma: Cardiac SurgeryBlunt chest trauma Radiation therapy Neurodegenerative: Myotonic dystrophyMuscular dystrophy Kearns-Sayre syndrome Infiltrative disorders: Tuberous SclerosisLymphoma AmyloidosisSarcoid Pharmacologic: Tricyclic antidepressantsAntiarrhythmic agents Digoxin 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 old30 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 - represents 90% of SVT in pediatric populations 3 Major Requirements: 1.2 pathways connected proximally and distally 2.Unidirectional block in one pathway 3.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 TachycardiaSinus 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 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 % 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 HeartAutomaticityReentry SA NodeSinus tachycardia SA node reentry Atrial muscleEAT/MATAflutter/Afib AV NodeJETAVNRT AV reciprocatingNAWPW/ Concealed AP VentriclesVT/VFVT

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 PulmonaryLiverThyroidSkin EyeGI tract

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 DiagnosisSuccess (%) WPW94 Concealed AP99 PJRT95 EAT100 Mahaim100 AVNRT83 Totals90 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%

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 Carto – Biosense Electroanatomical Mapping System Newer Mapping Strategies

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