AUTHOR INFORMATION

Section 1 of 10

Authored by Mirna M Farah, MD, Assistant Professor of Clinical Pediatrics, University of Pennsylvania School of Medicine; Consulting Staff, Division of Emergency Medicine, Children's Hospital of Philadelphia

Coauthored by Christine S Cho, MD, MPH, Instructor, Pediatrics, Division of Emergency Medicine, The Children's Hospital of Philadelphia

Mirna M Farah, MD, is a member of the following medical societies: American Academy of Pediatrics

Edited by David A Peak, MD, Instructor, Staff Physician, Department of Emergency Services, Massachusetts General Hospital, Harvard Medical School; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Grace M Young, MD, Associate Professor, Department of Pediatrics, University of Maryland Medical Center; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Richard G Bachur, MD, Assistant Professor of Pediatrics, Harvard Medical School; Associate Chief and Fellowship Director, Division of Emergency Medicine, Children's Hospital of Boston

Author's Email:	Mirna M Farah, MD
Editor's Email:	David A Peak, MD

eMedicine Journal, August 29 2006, VOLUME 7, Number 8

INTRODUCTION

Section 2 of 10

Background: Tachycardia is an abnormal rapidity of heart action that usually is defined as a heart rate more than 100 beats per minute (bpm) in adults. In children, the normal heart rate is age dependent, and the definition of tachycardia varies, as shown below.

• Age 1-2 days - 123-159 bpm

• Age 3-6 days - 129-166 bpm

• Age 1-3 weeks - 107-182 bpm

• Age 1-2 months - 121-179 bpm

• Age 3-5 months - 106-186 bpm

• Age 6-11 months - 109-169 bpm

• Age 1-2 years - 89-151 bpm

• Age 3-4 years - 73-137 bpm

• Age 5-7 years - 65-133 bpm

• Age 8-11 years - 62-130 bpm

• Age 12-15 years - 60-119 bpm

Pathophysiology: The heart is innervated primarily by the vagus nerve and the sympathetic ganglion. Pain sensation travels through afferent fibers associated with the sympathetic ganglia. In most patients, the sensation of a normal heartbeat is not felt. Some children may complain of palpitations or rushing or pounding in the ears.

CLINICAL

Section 3 of 10

History:

• Chest pain

• Palpitations

• Syncope

• Dizziness

• Shortness of breath

• Diaphoresis (for infants—while feeding)

• Color changes

• Neurologic changes (mental status, motor/sensory deficits)

• Decrease in intake and output

• Trauma

• Pain

• Fever

• Onset/duration of illness

• Relationship to exercise, meals, and stress

• Medical history, especially history of tachycardia or other cardiac problems

• Medications - Amphetamines, cocaine, caffeine, ephedrine, antihistamines, phenothiazines, antidepressants, theophylline, appetite suppressants, albuterol

• Allergies

• Family history of sudden death, deafness (Jervell-Lange Nielsen syndrome) or cardiac disease

Physical:

• General appearance

• Temperature

• Heart rate

• Respiratory rate

• Blood pressure

• Oxygen saturation

• Assessment of pain

• Decreased level of consciousness, decreased level of activity

• Jugular venous distention

• Neck mass

• Dyspnea, increased work of breathing, retractions

• Crackles, wheezing

• Cardiac gallop

• Cardiac murmur

• Increased liver size

• Abdominal mass

• Decreased urine output

• Poor peripheral perfusion (delayed capillary refill > 2 sec, cool extremities, pallor)

• Cyanosis

• Edema

Causes: Tachycardia can be due to a physiologic response of the heart to noncardiac stimuli or to a true dysrhythmia.

• Hyperdynamic cardiac activity

• Increased heart rate and contractility are physiologic responses to catecholamine release.

• Catecholamine release may occur with stress or anxiety, exercise, fever or infection, pain, anemia, seizure, hypovolemia, hypoxia, drugs or medications/stimulants (eg, amphetamines, cocaine, caffeine, ephedrine, antihistamines, phenothiazines, antidepressants, tobacco, theophylline, general anesthesia), vasodilation (eg anaphylaxis), oncologic mass (pheochromocytoma, neuroblastoma), hypoglycemia, hyperthyroidism, or acidosis.

• True dysrhythmias

• Supraventricular tachycardia (SVT)
  • Drug induced (eg, amphetamines, cocaine, caffeine, ephedrine, antihistamines, phenothiazines, antidepressants, tobacco, albuterol, theophylline, general anesthesia)

  • Wolff-Parkinson-White syndrome (WPW)

  • Hyperthyroidism

  • Congenital heart disease

  • Postoperative cardiac repair

• Atrial fibrillation or atrial flutter
  • Drug induced

  • Wolff-Parkinson-White syndrome (WPW)

  • Postoperative cardiac repair

  • Congenital or rheumatic mitral disease

  • Hyperthyroidism

• Junctional ectopic tachycardia (JET) - Postoperative cardiac repair

• Ventricular tachycardia (VT)
  • Drug induced (eg, tricyclics, phenothiazines, antiarrhythmics, chloral hydrate, organophosphates, hydrocarbons, digoxin, amphetamines, cocaine, arsenic)

  • Prolonged Q-T syndrome/torsades de pointes

  • Myocarditis

  • Rheumatic fever

  • Mitral valve prolapse

  • Cardiomyopathy

  • Myocardial ischemia

  • Postoperative cardiac repair

  • Hyperkalemia (peaked T waves, prolonged QRS and QT intervals)

  • Hypocalcemia (increased QT intervals secondary to ST-segment prolongation)

  • Hypokalemia (especially in association with digoxin use due to its synergistic effects on automaticity and conduction)

  • Hypomagnesemia (associated with hypocalcemia and hypokalemia)

  • Cardiac tumors

  • Arrhythmogenic right ventricular dysplasia

DIFFERENTIALS

Section 4 of 10

Anemia, Chronic
Atrial Fibrillation
Atrial Flutter
Hyperthyroidism, Thyroid Storm, and Graves Disease
Hypoglycemia
Pediatrics, Bacteremia and Sepsis
Pediatrics, Dehydration
Pediatrics, Diabetic Ketoacidosis
Torsade de Pointes
Toxicity, Amphetamine
Toxicity, Anticholinergic
Toxicity, Antidepressant
Toxicity, Antihistamine
Toxicity, Cocaine
Toxicity, Cyclic Antidepressants
Toxicity, Digitalis
Toxicity, Hallucinogen
Toxicity, Organophosphate and Carbamate
Toxicity, Sympathomimetic
Toxicity, Theophylline
Toxicity, Thyroid Hormone
Ventricular Tachycardia
Wolff-Parkinson-White Syndrome

WORKUP

Section 5 of 10

Lab Studies:

• Electrolytes - Particularly potassium, bicarbonate, calcium, and magnesium

• Blood glucose

• Complete blood count

• Toxicology screen

• Arterial blood gas

• Thyroid function tests

• Urine catecholamine metabolites (homovanillic and vanillylmandelic acid)

Imaging Studies:

• Chest radiography (posteroanterior and lateral)

• Echocardiogram

Other Tests:

• 12-lead electrocardiogram

• Cardiac rhythm strip

• Holter monitoring

• Event recorder

• Electrophysiology testing

TREATMENT

Section 6 of 10

Prehospital Care:

• Assess and stabilize airway, breathing, and circulation.

• Administer oxygen.

• Start intravenous (IV) fluids when indicated.

• Place a cardiorespiratory monitor.

Emergency Department Care: Treatment depends on the condition of the patient and the etiology of the tachycardia. The child who appears ill with tachycardia requires rapid assessment for the presence of hypoxemia, shock, hypoglycemia, or life-threatening dysrhythmia.

• Assess and support airway and breathing as needed. Direct treatment of sinus tachycardia toward reversing the underlying medical condition.

• Supraventricular tachycardia

• Asymptomatic patients or those with mild heart failure
  • Ice to face and vagal maneuvers: The diving reflex causes peripheral vasoconstriction and a vagally mediated decrease in cardiac output.

  • Adenosine: 0.1 mg/kg (max 6 mg) rapid IV push; if ineffective, the dose can be doubled to 0.2 mg/kg (max 12 mg). Complications may include bronchospasm (relatively contraindicated in patients with asthma), bradycardia, headache, shortness of breath, dizziness, and nausea.

  • Propranolol: 1 mg/kg/dose PO q6h

  • Digoxin: Total digitalizing dose (initial dosing) 10 mcg/kg IV in infants, 20 mcg/kg IV in older children; 1/2 dose stat, then 1/4 dose q8-12h X 2 (contraindicated in WPW)

  • Procainamide: 15-50 mg/kg/d PO divided in 6 doses

• Patients with moderate heart failure
  • Ice and vagal maneuvers

  • Adenosine IV (see above)

  • Amiodarone: 5 mg/kg IV over 20-60 min or procainamide 15 mg/kg IV over 30-60 min (do not routinely administer amiodarone and procainamide together)

  • Cardioversion, synchronized: 0.5-1 J/kg, doubling dose prn (up to 2 J/kg)

  • Propranolol: 0.01-0.1 mg/kg slow IV over 10 min

  • Digoxin IV (see above)

  • Rapid atrial pacing (esophageal or intracardiac)

• Patients with severe heart failure
  • Cardioversion, synchronized - Initial dose 0.5-1 J/kg (see above)

  • Adenosine IV (see above)

  • Amiodarone IV or procainamide IV (see above)

  • Propranolol IV (see above)

  • Digoxin IV (see above)

  • Rapid atrial pacing (esophageal or intracardiac)

• Atrial fibrillation or flutter

• For stable patients
  • Beta-blocker (eg, propranolol - 1 mg/kg/dose PO q6h)

  • Digoxin: Total digitalizing dose (initial dosing) 10 mcg/kg IV in infants, 20 mcg/kg IV in older children; 1/2 dose stat, then 1/4 dose q8-12h X 2 (contraindicated in WPW)

  • Amiodarone: 5 mg/kg IV over 20-60 min

  • Cardioversion: 0.5-1 J/kg; may repeat prn up to a total dose of 2 J/kg. Administer cardioversion earlier if signs of severe cardiac failure manifest or if deterioration occurs during medical treatment. If patient is stable and presenting with >48 hours of signs of atrial dysrhythmia, consider anticoagulation prior to cardioversion.

• For patients in shock
  • Immediate cardioversion: 0.5-1 J/kg; may repeat prn up to a total dose of 2 J/kg.

• Ventricular tachycardia

• For stable patients, consider the following medications in consultation with a pediatric cardiologist:
  • Amiodarone: 5 mg/kg IV over 20-60 min or procainamide 15 mg/kg IV over 30-60 min (do not routinely administer amiodarone and procainamide together)

  • Cardioversion: 0.5 J/kg; may increase to 1 J/kg then 2 J/kg if initial dose ineffective. Administer cardioversion earlier if signs of severe cardiac failure manifest or if deterioration occurs during medical treatment.

• Patients in shock and those with pulseless VT or ventricular fibrillation
  • Assess ABCs and secure IV access.

  • Start cardiopulmonary resuscitation (CPR) and ventilate with 100% oxygen (Do not delay defibrillation with these interventions).

  • Defibrillate once with 2 J/kg. May use AED for children aged > 1 year. Use the pediatric AED system if available for children aged 1-8 years.

  • Give 5 cycles of CPR.

  • Check rhythm and if shockable, defibrillate once with 4 J/kg.

  • Resume CPR immediately.

  • Administer epinephrine 0.01 mg/kg (1:10,000: 0.1 mL/kg) IV/IO or if via endotracheal tube (ET) 0.1 mg/kg (1:1000: 0.1 mL/kg). Repeat epinephrine q3-5min.

  • Give 5 cycles of CPR.

  • Check rhythm and if shockable, defibrillate once with 4 J/kg.

  • Consider lidocaine 1 mg/kg IV/IO/ET bolus

  • Consider amiodarone 5 mg/kg IV/IO

  • Consider magnesium 25-50 mg/kg IV/IO

  • If rhythm is nonshockable, resume CPR immediately and administer epinephrine as stated above.

Consultations: Consult a cardiologist for all cases of true dysrhythmia, particularly if the patient is unstable.

MEDICATION

Section 7 of 10

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Drug Category: Antiarrhythmic agents -- Alter the electrophysiologic mechanisms responsible for arrhythmia.

Drug Name	Adenosine (Adenocard) -- First-line medical treatment for termination of PSVT. Short-acting agent that alters potassium conductance into cells and results in hyperpolarization of nodal cells. This increases the threshold to trigger an action potential and results in sinus slowing and blockage of AV conduction. Effective in terminating both AVNRT and AVRT. More than 90% of patients convert to sinus rhythm with adenosine 12 mg. As a result of its short half-life, adenosine is best administered in an antecubital vein as an IV bolus followed by rapid saline infusion.
Adult Dose	Initial dose: 6 mg rapid IV bolus over 1-2 sec followed by a fluid bolus through a widely patent IV site; if no response within 1-2 min, give 12 mg rapid IV bolus; repeat 12 mg dose a second time Single doses >12 mg not generally recommended
Pediatric Dose	0.1 mg/kg IV and repeat at 0.2 mg/kg, if first dose not effective, not to exceed single dose of 12 mg Alternatively: 0.05 mg/kg IV and if not effective within 2 min, increase dose by 0.05 mg/kg increments q 2 min not to exceed 0.25 mg/kg
Contraindications	Documented hypersensitivity; second- or third-degree AV block or sick sinus syndrome (except in patients with functioning artificial pacemaker), atrial flutter, atrial fibrillation, and ventricular tachycardia
Interactions	Coadministration with carbamazepine may produce higher degrees of heart block; dipyridamole may potentiate effects of adenosine; methylxanthines may antagonize effects of adenosine
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Adenosine-induced bronchoconstriction in patients with asthma may occur; adverse effects include bronchospasm, flushing, chest pain, and brief asystole

Drug Name	Procainamide (Pronestyl) -- Class I-A antiarrhythmic. Increases refractory period of the atria and ventricles. Myocardiac excitability is reduced by an increase in threshold for excitation and inhibition of ectopic pacemaker activity. Indicated in recurrent VT not responsive to lidocaine, refractory SVT, refractory VF, pulseless VT, and AF with rapid rate in WPW.
Adult Dose	30 mg/min IV at continued infusion rates until arrhythmia is suppressed, patient becomes hypotensive, QRS widens 50% above baseline, or a maximum dose of 17 mg/kg is administered; may infuse at a continuous rate of 1-4 mg/min once arrhythmia is suppressed
Pediatric Dose	Not established Suggested dosing: 15-50 mg/kg/d PO divided q3-6h; 20-30 mg/kg/d IM divided q4-6h; not to exceed 4 g/d; 3-6 mg/kg/dose infused over 5 min; 20-80 mcg/kg/min administered as continuous infusion maintenance; not to exceed 100 mg/dose or 2 g/d
Contraindications	Documented hypersensitivity; complete heart block or second- or third-degree heart block, if a pacemaker is not in place; torsades de pointes; systemic lupus erythematosus
Interactions	Expect increased levels of procainamide metabolite NAPA in patients taking cimetidine, ranitidine, beta-blockers, amiodarone, trimethoprim and quinidine; may increase effect of skeletal muscle relaxants, quinidine and lidocaine and neuromuscular blockers; ofloxacin inhibits tubular secretion of procainamide and may increase bioavailability; when taken concurrently with sparfloxacin, may increase risk of cardiotoxicity
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in hypokalemia and hypomagnesemia; monitor for hypotension; plasma concentrations of procainamide and active metabolite, NAPA, may increase in renal failure; high or toxic concentrations may induce AV block or abnormal automaticity; caution in complete AV block, digitalis intoxication, organic heart disease, renal disease, and hepatic insufficiency

Drug Name	Digoxin (Lanoxin) -- Cardiac glycoside with direct inotropic effects in addition to indirect effects on the cardiovascular system. Acts directly on cardiac muscle, increasing myocardial systolic contractions. Its indirect actions result in increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure. Total digitalizing dose (TDD): Initially administer 50%; then, administer the remaining two 25% portions at 6-12 h intervals (ie, 1/2, 1/4, 1/4).
Adult Dose	Total digitalizing dose (TDD) to be administered over 24 h; first dose is one half the TDD; second dose is one fourth the TDD, administered 8 h later; third dose is one fourth the TDD, administered 8 h after the second TDD: 0.75-1.5 mg PO in divided doses over 1 d; alternatively 0.5-1 mg IV/IM in divided doses over 1 d Maintenance dose: 0.125-0.5 mg PO qd or 0.1-0.4 mg IV/IM qd
Pediatric Dose	Total digitalizing dose (TDD) to be administered over 24 h; first dose is one half the TDD; second dose is one fourth the TDD, administered 8 h later; third dose is one fourth the TDD, administered 8 h after the second TDD: Preterm infant: 20-30 mcg/kg PO or 15-25 mcg/kg IV in divided doses Term infant: 25-35 mcg/kg PO or 20-30 mcg/kg IV in divided doses 1-24 months: 35-60 mcg/kg PO or 30-50 mcg/kg IV/IM in divided doses 2-5 years: 30-40 mcg/kg PO or 25-35 mcg/kg IV/IM in divided doses 5-10 years: 20-35 mcg/kg PO or 15-30 mcg/kg IV/IM in divided doses >10 years: 10-15 mcg/kg PO or 8-12 mcg/kg IV/IM in divided doses Maintenance: Oral: Preterm infant: 5-7.5 mcg/kg/d PO divided bid Term infant: 6-10 mcg/kg/d PO divided bid 1-24 months: 10-15 mcg/kg/d PO divided bid 2-5 years: 7.5-10 mcg/kg/d PO divided bid 5-10 years: 5-10 mcg/kg/d PO divided bid >10 years: 2.5-5 mcg/kg PO qd Parenteral: Preterm infant: 4-6 mcg/kg/d IV divided bid Term infant: 5-8 mcg/kg/d IV divided bid 1-24 months: 7.5-12 mcg/kg/d IV/IM divided bid 2-5 years: 6-9 mcg/kg/d IV/IM divided bid 5-10 years: 4-8 mcg/kg/d IV/IM divided bid >10 years: 2-3 mcg/kg IV/IM qd
Contraindications	Documented hypersensitivity; beriberi heart disease; idiopathic hypertrophic subaortic stenosis; constrictive pericarditis; carotid sinus syndrome
Interactions	Medications that may increase digoxin levels include alprazolam, benzodiazepines, bepridil, captopril, cyclosporine, propafenone, propantheline, quinidine, diltiazem, aminoglycosides, PO amiodarone, anticholinergics, diphenoxylate, erythromycin, felodipine, flecainide, hydroxychloroquine, itraconazole, nifedipine, omeprazole, quinine, ibuprofen, indomethacin, esmolol, tetracycline, tolbutamide, and verapamil; medications that may decrease serum digoxin levels include aminoglutethimide, antihistamines, cholestyramine, neomycin, penicillamine, aminoglycosides, PO colestipol, hydantoins, hypoglycemic agents, antineoplastic treatment combinations (including carmustine, bleomycin, methotrexate, cytarabine, doxorubicin, cyclophosphamide, vincristine, procarbazine), aluminum or magnesium antacids, rifampin, sucralfate, sulfasalazine, barbiturates, kaolin/pectin, and aminosalicylic acid
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Hypokalemia may reduce positive inotropic effect of digitalis; IV calcium may produce arrhythmias in digitalized patients; hypercalcemia predisposes patient to digitalis toxicity, and hypocalcemia can make digoxin ineffective until serum calcium levels are normal; magnesium replacement therapy must be instituted in patients with hypomagnesemia to prevent digitalis toxicity; patients diagnosed with incomplete AV block may progress to complete block when treated with digoxin; exercise caution in hypothyroidism, hypoxia, and acute myocarditis

Drug Name	Propranolol (Inderal) -- Class II antiarrhythmic. Nonselective, beta-adrenergic receptor blocker with membrane-stabilizing activity that decreases automaticity of contractions. Do not administer IV dose faster than 1 mg/min.
Adult Dose	1 mg slow IVP over 10 min; repeat q5min; not to exceed 5 mg total cumulative dose
Pediatric Dose	0.01-0.1 mg/kg slow IVP over 10 min; not to exceed 1 mg/dose
Contraindications	Documented hypersensitivity; uncompensated congestive heart failure; bradycardia; cardiogenic shock; AV conduction abnormalities
Interactions	Coadministration with aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease propranolol effects; calcium channel blockers, cimetidine, loop diuretics, and MAOIs may increase toxicity of propranolol; toxicity of hydralazine, haloperidol, benzodiazepines, and phenothiazines may increase with propranolol
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; withdraw drug slowly and monitor closely

Drug Name	Epinephrine (Adrenalin) -- Has alpha-agonist effects that include increased peripheral vascular resistance, reversed peripheral vasodilatation, systemic hypotension, and vascular permeability. Beta-agonist effects include bronchodilatation, chronotropic cardiac activity, and positive inotropic effects. Indicated for ventricular fibrillation and pulseless VT (after defibrillation).
Adult Dose	1 mg IVP; may repeat q3-5min Alternatives: 2-5 mg IV q3-5min; escalating 1-, 3-, and 5-mg doses at 3-min intervals; 0.1 mg/kg q3-5min
Pediatric Dose	First dose: 0.01 mg/kg IV/IO (0.1 mL/kg of 1:10,000 solution) Subsequent doses: 0.1 mg/kg IV/IO (0.1 mL/kg of 1:1000 solution); repeat q3-5min Intratracheal: 0.1 mg/kg IV/IO (0.1 mL/kg of 1:1000 solution)
Contraindications	Documented hypersensitivity; angle-closure glaucoma; local anesthesia in areas such as fingers or toes because vasoconstriction may produce sloughing of tissue; do not use during labor (may delay second stage of labor)
Interactions	Increases toxicity of beta- and alpha-blocking agents and that of halogenated inhalational anesthetics
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in older persons, prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac arrhythmias; adverse effects include tachycardia, palpitations, and anxiety

Drug Name	Amiodarone (Cordarone) -- Class III antiarrhythmic. Has antiarrhythmic effects that overlap all 4 Vaughn-Williams antiarrhythmic classes. May inhibit A-V conduction and sinus node function. Prolongs action potential and refractory period in myocardium and inhibits adrenergic stimulation. Only agent proven to reduce incidence and risk of cardiac sudden death, with or without obstruction to LV outflow. Very efficacious in converting atrial fibrillation and flutter to sinus rhythm and in suppressing recurrence of these arrhythmias. Has low risk of proarrhythmia effects, and any proarrhythmic reactions generally are delayed. Used in patients with structural heart disease. Most clinicians are comfortable with inpatient or outpatient loading with 400 mg PO tid for 1 wk because of low proarrhythmic effect, followed by weekly reductions with goal of lowest dose with desired therapeutic benefit (usual maintenance dose for AF 200 mg/d). During loading, patients must be monitored for bradyarrhythmias. Prior to administration, control the ventricular rate and CHF (if present) with digoxin or calcium channel blockers. Oral efficacy may take weeks. With exception of disorders of prolonged repolarization (eg, LQTS), may be DOC for life-threatening ventricular arrhythmias refractory to beta-blockade and initial therapy with other agents.
Adult Dose	150 mg IV infused over 10 min, follow with 1 mg/min constant infusion for 6 h, then maintenance infusion at 0.5 mg/min Oral dosing generally 400 mg/d following load
Pediatric Dose	Not established; weight-based dosing suggested; consider for refractory ventricular arrhythmias in children
Contraindications	Documented hypersensitivity, complete A-V block, and intraventricular conduction defects; patients taking ritonavir or sparfloxacin
Interactions	Increases effect and blood levels of theophylline, quinidine, procainamide, phenytoin, methotrexate, flecainide, digoxin, cyclosporine, beta-blockers, and anticoagulants; cardiotoxicity of amiodarone is increased by ritonavir, sparfloxacin, and disopyramide; coadministration with calcium channel blockers, may cause an additive effect and decrease myocardial contractility further; cimetidine may increase amiodarone levels; protease inhibitors (eg, indinavir, ritonavir, amprenavir, nelfinavir) inhibit amiodarone metabolism resulting in increased serum levels and may prolong QT interval; coadministration may increase myopathy/rhabdomyolysis risk associated with HMG-CoA reductase inhibitors (eg, simvastatin); other drugs that prolong the QT interval (eg, fluoroquinolones, erythromycin, dofetilide, tricyclic antidepressants, thioridazine) may increase life-threatening arrhythmia risk
Pregnancy	D - Unsafe in pregnancy
Precautions	Known to cause serious (and at times fatal) toxicities including pulmonary and liver toxicities; may cause prolonged proarrhythmic effects; may cause optic neuritis/neuropathy or hypothyroidism or hyperthyroidism; CNS and GI toxicity may occur and typically dissipates with dose reduction

Drug Name	Lidocaine (Xylocaine) -- Class IB antiarrhythmic that increases electrical stimulation threshold of the ventricle, suppressing automaticity of conduction through the tissue.
Adult Dose	1-1.5 mg/kg IV bolus initially over 2-3 min; repeat doses of 0.5-0.75 mg/kg in 5-10 min, not to exceed a total of 3 mg/kg, followed by 2-4 mg/min IV
Pediatric Dose	1-2 mg/kg IV/IO bolus initially, followed by 10-50 mcg/kg/min IV
Contraindications	Documented hypersensitivity to amide-type local anesthetics; avoid in Adams-Stokes syndrome and WPW syndrome; avoid in severe sinoatrial, AV, or intraventricular block, if artificial pacemaker not in place
Interactions	Coadministration with cimetidine or beta-blockers increases toxicity; coadministration with procainamide and tocainide may result in additive cardiodepressant action; may increase effects of succinylcholine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Use a solution without preservatives; caution in heart failure (decrease bolus and maintenance doses), hepatic disease, hypoxia, hypovolemia or shock, respiratory-depression and bradycardia; may increase risk of CNS and cardiac adverse effects in older persons; high plasma concentrations can cause seizures, heart block, and AV conduction abnormalities

Drug Name	Magnesium sulfate -- DOC for torsade de pointes, it also may be useful to treat conventional VT, especially where hypomagnesemia is confirmed. When treating with magnesium sulfate, monitor for hypermagnesemia since an overdose can cause cardiorespiratory collapse and paralysis.
Adult Dose	1-2 g diluted in 100 mL of D5W IV over 1-2 min for refractory VT and known or suspected hypomagnesemia (Mg+2 <1.4 mEq/L); not to exceed 30-40 g/d; maximum rate of infusion for maintenance not to exceed 1-2 g/h
Pediatric Dose	Not established Suggested dose: 25-50 mg/kg IV q4-6h for 3-4 doses; maximum single dose of 2 g also may be administered and repeated if hypomagnesemia persists
Contraindications	Documented hypersensitivity; heart block, Addison disease, myocardial damage, or severe hepatitis
Interactions	Concurrent use with nifedipine may cause hypotension and neuromuscular blockade; may increase neuromuscular blockade seen with aminoglycosides and potentiate neuromuscular blockade produced by tubocurarine, vecuronium, and succinylcholine; may increase CNS effects and toxicity of CNS depressants, betamethasone, and cardiotoxicity of ritodrine
Pregnancy	A - Safe in pregnancy
Precautions	Magnesium may alter cardiac conduction leading to heart block in digitalized patients; respiratory rate, deep tendon reflex, and renal function should be monitored when electrolyte is administered parenterally; caution when administering magnesium dose since may produce significant hypotension or asystole; in overdose, calcium gluconate, 10-20 mL IV of 10% solution, can be given as antidote for clinically significant hypermagnesemia

FOLLOW-UP

Section 8 of 10

Patient Education:

• For excellent patient education resources, visit eMedicine’s Heart Center. Also, see eMedicine’s patient education articles Supraventricular Tachycardia and Palpitations.

TEST QUESTIONS

Section 9 of 10

CME Question 1: A 4-month-old infant presents with a heart rate of 185 beats per minute (bpm). He is asymptomatic and has benign physical examination findings. What is the first step in management?

A: Obtain a 12-lead ECG
B: Consult a pediatric cardiologist.
C: Perform vagal maneuvers to slow his heart rate.
D: Send him home on no medication.
E: Place him on a cardiac monitor, and transfer him to the nearest ED for further treatment.

The correct answer is D: A heart rate of 185 bpm is normal for a 4-month-old infant. Since the patient is asymptomatic with normal physical examination findings, no further care is needed.

CME Question 2: Which of the following is not a common presentation of supraventricular tachycardia (SVT) in infants?

A: Sweating
B: Poor feeding
C: Irritability
D: Tachypnea
E: Syncope

The correct answer is E: Syncope is a very rare presentation of SVT in children. Most infants tolerate SVT for hours. Poor feeding (essentially, a form of exercise for the infant), tachypnea (from pulmonary veinous congestion), sweating (due to a high catecholamine state), and irritability are the physical findings that establish an early diagnosis.

Pearl Question 1 (T/F): Defibrillation is the treatment of choice for unstable children with wide complex tachycardia.

The correct answer is True: Children with wide complex tachycardia should be treated as if they had ventricular tachycardia. Defibrillation is the treatment of choice for unstable children.

Pearl Question 2 (T/F): All of the following are potential treatments for stable ventricular tachycardia: lidocaine, amiodarone, procainamide, and cardioversion.

The correct answer is True: The four interventions listed are all potential treatments for stable ventricular tachycardia.

Pearl Question 3 (T/F): Sinus tachycardia is indicative of an underlying cardiac anomaly in children.

The correct answer is False: Sinus tachycardia is most commonly due to a noncardiac etiology in children. Often, it represents a physiologic response to catecholamine release, which may occur with hypovolemia, fever, pain, anxiety, or anemia.

Pearl Question 4 (T/F): Vagal maneuvers are contraindicated in infants with asymptomatic supraventricular tachycardia (SVT).

The correct answer is False: Vagal maneuvers (eg, ice on the face) should be performed on infants with asymptomatic SVT as the initial step to slow the heart rate prior to drawing any medication. If performed properly, the diving reflex is safe and effective in slowing the heart rate.

BIBLIOGRAPHY

Section 10 of 10

• Gewitz MH, Woolf PK: Cardiac emergencies. In: Fleisher GR, Ludwig S, eds. Textbook of Pediatric Emergency Medicine. 5th ed. 2006:717-758.
• Greene MG, ed: The Harriet Lane Handbook. 12th ed. 1991:80.
• Kaltman J, Shah M: Evaluation of the child with an arrhythmia. Pediatr Clin North Am 2004 Dec; 51(6): 1537-51, viii[Medline].
• PDR: Physicians' Desk Reference. 47th ed. 1993:1035.
• Pediatric Advanced Life Support: American Heart Association. Circulation 2005; 112: IV167-87.
• Perondi MB, Reis AG, Paiva EF, et al: A comparison of high-dose and standard-dose epinephrine in children with cardiac arrest. N Engl J Med 2004 Apr 22; 350(17): 1722-30[Medline].
• Strasburger JF: Cardiac arrhythmias in childhood. Diagnostic considerations and treatment. Drugs 1991; 42(6): 974-83[Medline].
• Whitman V, Friedman Z, Berman W Jr: Supraventricular tachycardia in newborn infants: an approach to therapy. J Pediatr 1977; 91(2): 304-5[Medline].
• Wiley JF: Tachycardia/palpitations. In: Fleisher GR, Ludwig S, eds. Textbook of Pediatric Emergency Medicine. 5th ed. 2006:657-668.
• Yabek SM: Ventricular arrhythmias in children with an apparently normal heart. J Pediatr 1991; Jul 119(1): 1-11[Medline].
• Zaritsky AL, ed: Cardiac rhythm disturbances. In: Textbook of Pediatric Advanced Life Support. 2002:85-228.

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