Supraventricular Tachycardia In Infants & Children

Transcription

1 1 Supraventricular Tachycardia In Infants & Children Peggy Dorr, MS, CRNP Pediatric Nurse Practitioner The Children s Heart Program University of Maryland Medical Center 2 Incidence! Affects 1:25,000 to 1:250 children! 50% present with their initial episode in first year of life! After infancy, incidence peaks in early childhood (6-9 years), then again in adolescence! Spontaneous resolution occurs in more than 90% of infants by 1 year old but 1/3 of those will recur by 8y.o. 3 The Normal Conduction Cycle

2 4 SVT - definition! Sustained tachyarrhythmia originating above the bundle of His Hanisch, 2001 PALS/AHA Guidelines use the following rate criteria:! infants > 220 bpm! children >160 bpm as well as narrow complex with no rate variability 5 Epidemiology! SVT 7% have 1 st degree relative! Wolff-Parkinson-White (WPW) Syndrome 3x greater than general population have affected 1 st degree relative with WPW 6 Pathophysiology of SVT s! 3 most common mechanisms:! Accessory pathway mediated re-entry tachycardia (aka - atrioventricular reciprocating tachycardia - AVRT)! Atrioventricular nodal re-entry tachycardia (AVNRT)! Atrial ectopic tachycardia (AET)

3 7 Accessory Pathway Mediated Re- Entry Tachycardia! Cause of approximately 75% of all SVT cases! One or more accessory conduction pathways that are anatomically separate from normal conduction pathway! Electrical conduction usually travels antegrade down AV node and retrograde up the accessory pathway (AP)! May be overt (seen on ECG) or concealed 8 Accessory Pathways 9 Wolff-Parkinson White Syndrome! Example of an overt, orthodromic accessory pathway mediated tachycardia! May be genetic; autosomal dominant pattern! Increased association with: Ebstein s anomaly, tricuspid atresia, DORV and HOCM! AP known as either Kent bundle or a bypass tract

4 10! Identifiable on ECG by:! Short PR interval! Presence of Delta Wave! Wide QRS complex 11! WPW cont d! During SVT conduction a loop is formed between Kent bundle and AV node! Rapid conduction of a- fib over the AP to ventricles can result in v-fib. Can lead to syncope, cardiac arrest, death Conditions/DS00923.cfm

5 13 14 AVNRT! 2 nd most common pathway in children (15% of cases)! Will have a dual-nodal physiology at the AV node! Fast pathway! Slow pathway 15

6 16! AVNRT occurs when there is antegrade conduction block over the fast pathway which results in conduction over the slow pathway.! By the time conduction has occurred over the slow pathway, the fast pathway has recovered and conduction is able to proceed retrograde over the fast pathway AVNRT mechanism! Typically triggered when a PAC occurs during the refractory phase of the fast pathway

7 19 Atrial Ectopic Tachycardia (AET)! Abnormal electrical impulse that originates outside of sinus node! Most common mechanism of incessant tachycardia in children! Appears to be due to abnormal automaticity of cells (perhaps caused by remnant embryonic cells with automatic qualities) 20 AET! Low incidence; most common in very young infants/children! Rates can range from (agedependent)! Tachycardia induced cardiomyopathy can develop 21 Manifestation of these extra pathways! Dysrhythmias! Palpitations (anxiety, missed school)! Medications! Changes in lifestyle (activities, driving)! Parental stress! Syncope! Increased risk of sudden death

8 22 Acute Management! Will depend on stability of patient! Vagal maneuvers! increase the parasympathetic tone which results in transient AV block! Examples of vagal maneuvers include:! Ice/water to face (diving reflex)! Cough/gag 23 Adenosine Dose: 0.1mg/kg! Rapid IV push! No dilution, follow with large flush! Give in access closest to central circulation! May repeat at same or higher dose with max single recommended dose = 0.3mg/kg 24 Synchronized Cardioversion! Synchronized cardioversion! 0.5-1j/kg! Sync with rhythm! Repeat if necessary! A/P placement of pads can be successful! Sedate if necessary

9 25 Next level of acute management! Amiodarone (bolus/infusion)! Class III antiarrhythmic! Correct K & Mg! Pro-arrhythmic! Hypotension if given too fast/too much! Prolonged QT interval w/specific ab s! Load w/5mg/kg IV over 30-60! LT: check LFT s, TFT s, PFT s, CXR 26! Procainamide infusion! Class IA antiarrhythmic! Pro-arrhythmic! Prolonged QT interval! Hypotension! Load w/3-6mg/kg/dose over 5 (not greater than 100mg/dose). Maintenance infusion mcg/kg/min. Can check levels 27 LT Management! Digoxin! Negative chronotrope, negative dromotrope.! NOT TO BE USED WITH WPW PATIENTS can accelerate antegrade conduction through accessory pathway during a-fibrillation! PO Dose: 10mcg/kg/day divided BID in children! Levels not routinely monitored

10 28! Propranalol (Inderal)! Negative chronotrope, negative dromotrope! Non selective β-blocker watch for respiratory complications! PO dose: 2-4mg/kg/day divided q 6-8 hours 29 Other medications! Flecainide! Sotalol! Propafenone 30 Long Term Issues! Infants:! Teach parents to check HR at brachial site; may give stethescope! Watch for change in behavior just not acting right! Will need to increase dose of antiarrhythmics as they grow! At 9-10 months, usually let them outgrow meds and see what happens

11 31! Children! Present in clinic with c/o palpitations! Can be real or just an awareness of heart beating! Event monitor 30 days! Adolescents! Same as above! Anxiety can play a role! Compliance with medications may be an issue 32 Life Style Changes! NO Activity Restrictions! Should be cautious with medications that can increase HR (stimulants, cold meds)! Limit caffeine intake Based on the frequency of breakthrough events or desire to be rid of medications, more decisive therapy may be discussed. 33 The Electrophysiologic (EP) Study! Diagnose mechanism and anatomy of dysrhythmia! Eliminate dysrhythmia with ablation

12 34 Pros and Cons! POSITIVES! Non-surgical! Eliminate need for LT medications! Prevent sudden death events! NEGATIVE! Smaller heart! Less thick myocardium! Greater risks proven in children <4 y.o.! Risk for more morbidity (AV Block, need for pacemaker)! Can be unsuccessful 35 Catheter Placement! Groin access w/ passage of 4 catheters:! High Right Atrium! His Bundle! Coronary Sinus! RV Apex 36 Radiofrequency Ablation! Radiofrequency current causes resistive heating! Causes death to surrounding tissues via conduction of thermal energy

13 37 Cryoablation! Cools tissue to cause damage/destruction! Lesions can be reversible! Can apply at colder temperature to destroy 38 Success Rates! 1991 voluntary registry of pediatric ablation procedures initiated! AVNRT 97%, 97%, 60% (w/chd)! A. tachy 82%, 86.7%, 86% (w/chd)! A. flutter 91%, 84.8%, 55% (w/chd)! V. tach 79.7%, 53% (w/chd) (data from Lee article, Friedman article, Friedman article respectively) 39 Common Complications of EPS and RF Ablation! Varying degrees of heart block! Perforation of heart! Pericardial effusion! Embolization! Brachial plexus injury! Pneumothorax