Cardiac Arrhythmias

Rhythm originating from the Sinus Node

• Regular Sinus Rhythm – regular rate, P-axis 0–90°
• Sinus Tachycardia – sinus rhythm with higher rate than normal for age
• Sinus Bradycardia – sinus rhythm with lower rate than normal for age
• Sinus Arrhythmia – RR interval increases with inspiration and decreases with expiration, normal finding
• Sinus Pause – no P wave or QRS complex for a relatively short time; Cause:
Increased vagal tone, hypoxia, digitalis toxicity, sick sinus syndrome.
Hemodynamically insignificant.
• Sick Sinus Syndrome – sinus node dysfunction leading to brady- and
tachyarrhythmias. After heart surgery involving atria, myocarditis, idiopathic.
Tx depends on type of arrhythmia. Long-term tx is pacemaker.

Rhythms originating from the Atrium
- Abnormal P waves, normal QRS complex

• Premature Atrial Contraction – P upright in II when focus high, negative when
low in atrium. Compensatory pause is incomplete. Seen in healthy children, after
heart surgery or with Digoxin intoxication
• Wandering Atrial Pacemaker – varying P waves and PR intervals. In healthy
children
• Atrial Tachycardia – type of SVT (see below)
• Atrial Flutter – atrial rate 300/min with 2-4:1 block and normal QRS
complexes, “sawtooth” configuration. Seen after atrial surgery, in atrial
dilation, Digitalis toxicity, myocarditis. If hemodynamically stable start
Digoxin and/or Propranolol to slow down ventricular rate, if unsuccessful start
Amiodarone; Warfarin x 3-4 weeks before scheduled cardioversion. If unstable
cardiovert and start on Heparin. CAVE: d/c Digoxin 48h pre cardioversion.
• Atrial Fibrillation – atrial rate 350-600 bpm; causes and treatment same as
for atrial flutter.

SVT

• Types:
- AV reentry tachycardia (most common; WPW)
- AV nodal tachycardia (becomes more common with age; HR 120-200/min)
- Ectopic atrial tachycardia (rapid firing of single atrial focus; + variability in HR throughout day;
adenosine not effective)
• Causes: idiopathic, WPW, underlying CHD (esp. Ebstein’s anomaly), after heart
surgery, intracardiac tumors, iatrogenic (central line in RA)
• EKG: HR > 200-220 with regular RR interval (no variation with respiration), P
wave not seen (hidden in T wave) or has abnormal axis, QRS normal (except in
antidromic AVRT)
• Presentation: tolerated well but if prolonged (>12-24h) esp. infants may
present in CHF with pallor, tachypnea, sweating, poor feeding
• Treatment:
1. Vagal maneuvers: infants: ice bag in face x 10 sec; children: Valsalva
maneuver, carotid massage)

2. Adenosine:
• Causes transient AV block (T1/2 = 1.5 sec)
• Use as treatment for SVT or to unmask other narrow- and wide complex regular
(NOT irregular) tachycardias. Does not convert in AET, A fib/flutter or VT.
Dose: start with 0.1 mg/kg (max. 6 mg), if no effect after 1 min give 0.1
mg/kg/dose, then 0.15 mg/kg/dose etc. until max. single dose is 0.4mg/kg (max.
12 mg)
• Side effects: flushing, nasea, chest pain, bronchospasm, rarely atrial
fibrillation, ventricular tachycardia, prolonged asystole, apnea

3. Synchronized cardioversion: 0.5 J/kg to 1 J/kg up to 2 J/kg. Sedate if
possible.
Consult pediatric cardiology prior to using these

4. Procainamide:
• Slows conduction within myocardium, safe in WPW.
• Dose: Loading dose for <1y/o 7-10mg/kg, for >1y/o 15mg/kg iv over 30-45 min,
then 40-50mcg/kg/min.
• Check level 4 h after loading dose finished (while on maintenance Procainamide
infusion). Check BPs (neg. inotropy), serial EKGs (prolongs QT interval)

5. Amiodarone:
• Prolongs refractory period of AV node and myocardium, safe in WPW.
• Dose: Loading dose 5 mg/kg iv over 20-60 min. If no response repeat until
total dose is 20 mg/kg. If response, start continuous infusion of 10-15mg/kg/day
• serial EKGs (prolongs QT interval)

6. Transesophageal overdrive pacing

Rhythms originating from the Atrioventricular Node

• Nodal Premature Beats – premature QRS complex with normal configuration, may
be followed by inverted P-wave; complete or incomplete compensatory pause. Seen
in healthy children, after heart surgery or with Digoxin intoxication
• Nodal Escape Beats – occurs when sinus node impulse does not reach AV node;
seen in healthy children or after atrial surgery
• Nodal or Junctinal Rhythm – AV node takes over sinus node function at a lower
rate (40-60/min). Seen in after heart surgery, in increased vagal tone
(increased ICP, pharyngeal stimulation, in healthy children while asleep),
digitalis toxicity. No treatment if asymptomatic; if symptomatic give atropine,
external pacing, treat digitalis toxicity
• Accelerated Nodal Rhythm – enhanced automaticity of the AV node that
supersedes the sinus node rate. HR 60-120/min.
• Nodal Tachycardia – type of SVT

Rhythms originating from the Ventricle

• Premature Ventricular Contraction – premature wide QRS complex with inverted T
wave, not preceded by P wave, compensatory pause; may occur as single PVCs,
bigeminus, trigeminus, couplet or triplet. > 3 consequent PVCs = VT; may be
multifocal or unifocal. Causes: in healthy children (PVCs), myocardial
pathology, LQT, CHD, MVP, digitalis toxicity, catecholamines, theophylline,
caffeine, amphetamines, some anaesthetics. Workup: EKG, echo, stress test,
Holter. Beningn if occasional uniform PVCs (treat only if >10.000/day) that
decrease in frequency with exercise. Not benign if cardiac risk factors in
history.
• Ventricular Tachycardia
• Definition: series of three or more PVCs with a HR = 120 – 200 bpm
• EKG: QRS complexes are wide and bizarre, with T waves pointing in opposite
directions, no P waves seen; monomorphic vs polymorphic QRS complexes;
Non-sustained vs sustained VT (</> 30 sec)
• CAVE: Distinguish from SVT with wide QRS complexes and R/LBBB
• Causes: myocarditis, cardiomyopathy, RV dysplasia, CHD, LQT, mediaction
(Digitalis, TCA, catecholamines, theophylline, caffeine, amphetamines, and some
anesthetic agents, chlorothiazines, erythromycin, Bactrim, organophosphate
insecticides, some class I and III antiarrhythmic drugs like procainamide,
flecainide, amiodarone)
• See PALS protocol for management for VT with or without pulse

• Ventricular Fibrillation – see PALS algorithm