History

Fact Explanation
Awareness of the rapid heart rate which is of abrupt onset and cessation [1] Supraventricular tachycardias (SVTs) involve components of the conduction system within or above the bundle of His . Re-entry using an accessory pathway is the most common mechanism of SVT in infants. Some mechanisms of SVT are associated with congenital heart disease; however most children with SVT have structurally normal hearts.[2]
Precordial discomfort and heart failure [1] When the heart rate is exceptionally rapid or if the attack is prolonged only.
Sudden death[1] AV re-entrant tachycardia uses a bypass tract that may either be able to conduct antegrade (Wolff-Parkinson-White [WPW] syndrome. If the accessory pathway rapidly conducts in antegrade fashion, the patient is at risk for atrial fibrillation begetting ventricular fibrillation, consequent sudden death.[1]
Exercise induced syncope[3] Due to cardiac rhythm disturbance. [3]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007
  2. HAFEZ M, ABU-ELKHEIR M, SHOKIER M, AL-MARSAFAWY H, ABO-HADED H, EL-MAATY MA. Radiofrequency catheter ablation in children with supraventricular tachycardias: intermediate term follow up results. Clin Med Insights Cardiol [online]. 2012;6:7-16 [viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256955/
  3. AKDENIZ C, OZYLIMAZ I, SAYGI M, ERGUL Y, TUZCU V. Idiopathic ventricular arrhythmias detected by an implantable loop recorder in a child with exercise-induced syncope. Tex Heart Inst J [online]. 2013;40(3):347-9.[viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709205/

Examination

Fact Explanation
Tachycardia (>180 beats per minute) Heart rate in SVT tends to be unvarying, whereas in sinus tachycardia the heart rate varies with changes in vagal and sympathetic tone. [1] Supraventricular tachycardias (SVTs) involve components of the conduction system within or above the bundle of His . Re-entry using an accessory pathway is the most common mechanism of SVT in infants. Some mechanisms of SVT are associated with congenital heart disease; however most children with SVT have structurally normal hearts.[2]
Symptoms of heart failure in infants such as cyanosis , restlessness/irritability, tachypnoea, hepatomegaly. [1] Heart rate at this age is normally rapid and, even in the absence of tachyarrhythmia, it increases greatly with crying. Infants with SVT are often initially seen in heart failure because the tachycardia goes unrecognized for a long time.[1]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007

Differential Diagnoses

Fact Explanation
Sinus tachycardia [1] Sinus tachycardia the heart rate varies with changes in vagal and sympathetic tone [1]
Ventricular tachycardia [1] The absence of ventricular-to-atrial conduction (and thus only intermittent P waves), the presence of fusion beats, and wide QRS complexes that are dissimilar to the QRS complex during sinus rhythm are diagnostic of ventricular tachycardia [1]
AV nodal re-entrant tachycardia [1] Involves the use of two pathways within the AV node. This arrhythmia is more commonly seen in adolescence. It is one of the few SVTs that is frequently associated with syncope [1]
Atrial ectopic tachycardia [1] An uncommon tachycardia in childhood. It is characterized by a variable rate (seldom >200 beats/min), identifiable P waves with an abnormal axis, and chronicity in either a sustained or intermittent tachycardia. This form of atrial tachycardia has a single automatic focus rather than the more usual re-entry mechanism [1]
Chaotic or multifocal atrial tachycardia [1] This arrhythmia occurs most often in infants younger than 1 yr, usually without cardiac disease, although some evidence suggests an association with viral myocarditis. Drug treatment may not be effective, and multiple agents are often required. Fortunately, when this arrhythmia occurs in infancy, it usually terminates spontaneously by 3 yr of age. [1]
Accelerated junctional ectopic tachycardia (JET) [1] An automatic (non-re-entry) arrhythmia in which the junctional rate exceeds that of the sinus node and AV dissociation results. This arrhythmia is most often recognized in the early postoperative period after cardiac surgery and may be extremely difficult to control.[1]
Atrial flutter [1] This is an intra-atrial re-entrant tachycardia, is a regular or regularly irregular tachycardia characterized by atrial activity at a rate of 250–400 beats/min. These contractions are thought to be due to a re-entrant or circus rhythm originating in the atria and involving a micro-re-entrant loop within the atrial tissue and some form of anatomic obstacle that creates a discontinuity in conduction (fibrosis, surgical suture site, valve annulus). [1]
Atrial fibrillation [1] This is much less common in children and rare in infants. The atrial excitation is chaotic and more rapid (300–700 beats/min) and produces an irregularly irregular ventricular response and pulse ( Fig. 435-8 ). This rhythm disorder is most often the result of a chronically stretched atrial myocardium. Atrial fibrillation occurs most frequently in older children with rheumatic mitral valve disease. It is also seen rarely as a complication of intra-atrial surgery, in patients with left atrial enlargement secondary to left AV valve insufficiency, in conditions producing atrial flutter, and in patients with WPW syndrome. Thyrotoxicosis, pulmonary emboli, and pericarditis should be suspected in a previously normal older child or adolescent with atrial fibrillation. Atrial fibrillation may be familial.[1]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007

Investigations - for Diagnosis

Fact Explanation
Electrocardiogram [1] In neonates, SVT is usually manifested as a narrow QRS complex (<0.08 sec). The P wave is visible on a standard electrocardiogram in only 50–60% of neonates with SVT, but it is detectable with a transesophageal lead in most patients.[1]
Twenty-four hour electrocardiographic (Holter) recordings [1] It is useful in monitoring the course of therapy and in detecting brief runs of asymptomatic tachycardia[1]
Transesophageal pacing [1] A brief assessment of arrhythmia control can be made at the bedside using this [1]
Electrophysiologic study [1] Multiple electrode catheters are placed in different locations in the heart and can aid in pinpointing an ectopic focus or bypass tract.[1]
Graded exercise testing [2] This could be udes as an ideal noninvasive provocative test for SVT induction in suspected cases [2]
An implantable loop recorder [3] Implantable loop recorders can play an important role in the diagnosis of life-threatening arrhythmias in children whose syncope is otherwise unexplained.[3]
Echocardiography [3] To identify any structural heart disease [3]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007
  2. DRAPER DE, GIDDINS NG, McCORT J, GROSS GJ. Diagnostic usefulness of graded exercise testing in pediatric supraventricular tachycardia. Can J Cardiol [online]. 2009;25(7):407-10 [viewed on 20th April] available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2723024/
  3. AKDENIZ C, OZYLIMAZ I, SAYGIi M, ERGUL Y, TUZCU V. Idiopathic ventricular arrhythmias detected by an implantable loop recorder in a child with exercise-induced syncope. Tex Heart Inst J [online]. 2013;40(3):347-9.[viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709205/

Investigations - Fitness for Management

Fact Explanation
Echocardiography [1] To identify any structural heart disease [1]
Twenty-four hour electrocardiographic (Holter) recordings [2] As prerequisites to radiofrequency ablation [2]
Transesophageal pacing [2] As prerequisites to radiofrequency ablation [2]
Electrophysiologic study [2] As prerequisites to radiofrequency ablation [2]
References
  1. AKDENIZ C, OZYLIMAZ I, SAYGI M, ERGUL Y, TUZCU V. Idiopathic ventricular arrhythmias detected by an implantable loop recorder in a child with exercise-induced syncope. Tex Heart Inst J [online]. 2013;40(3):347-9.[viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709205/
  2. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007

Investigations - Followup

Fact Explanation
Twenty-four hour electrocardiographic (Holter) recordings [1] These are useful in monitoring the course of therapy and in detecting brief runs of asymptomatic tachycardia [1]
Transesophageal pacing [1] A brief assessment of arrhythmia control can be made at the bedside [1]
Echocardiography [2] To identfy any sign of heart failure [2]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007
  2. AKDENIZ C, OZYLIMAZ I, SAYGI M, ERGUL Y, TUZCU V. Idiopathic ventricular arrhythmias detected by an implantable loop recorder in a child with exercise-induced syncope. Tex Heart Inst J [online]. 2013;40(3):347-9.[viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709205/

Investigations - Screening/Staging

Fact Explanation
Twenty-four hour electrocardiographic (Holter) recordings [1] These are useful in monitoring the course of therapy and in detecting brief runs of asymptomatic tachycardia [1]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007

Management - General Measures

Fact Explanation
Circulatory and respiratory support (positive pressure ventilation if required) [1] For the correction of tissue acidosis [1]
Vagal stimulating manoeuvres Following maneuvers can be attempted: submersion of the face in iced saline (in older children) , placing an ice bag over the face (in infants) ,carotid sinus massage, in order to abolish the paroxysm, older children may be taught vagotonic maneuvers such as the Valsalva maneuver, straining, breath holding, drinking ice water, or adopting a particular posture. [2]
Intravenous Adenosine [1] This is the treatment of choice. It terminates tachycarida by breaking the re entry circuit that is set up between the atrioventricular node and the accessory pathway [1]
Electrical cardioversion with a synchronized DC shock (0.5-2 J/kg) [1] In urgent situations when symptoms of severe heart failure have already occurred [1]
References
  1. LISSAUER, Tom. CLAYDEN, Graham. Illustrated textbook of Paediatrics. 3rd ed. London: Mosby Elsevier, 2007
  2. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007

Management - Specific Treatments

Fact Explanation
Pharmacological management with Anti Arrhythmic agents [1] digoxin or propranolol, procainamide, quinidine, flecainide, propafenone, sotalol can be used to convert into sinus rhythm. In children with evidence of pre-excitation (WPW syndrome), digoxin or calcium channel blockers may increase the rate of anterograde conduction of impulses through the bypass tract and should be avoided. These patients are usually managed in the long term with propranolol [1]
Radiofrequency ablation or cryoablation of the accessory pathway. [2], [3], [4] For ablation of the accessory pathway. It is often used electively in children and teenagers, as well as in patients who require multiple agents or find drug side effects intolerable or for whom arrhythmia control is poor. The overall initial success rate ranges from approximately 80% to 95%, depending on the location of the bypass tract or tracts [1]
Surgical ablation [1] For ablation of the accessory pathway in selected patients [1]
References
  1. DUBIN, Anne. Cardiac Arrhythmias. In KLIGEMAN, Robert M, BEHRMAN, Richard E, JENSON, Hal B and STANTON, Bonita F. Nelson textbook of Paediatrics. 18th ed. Philadelphia: Saunders Elsevier, 2007
  2. LISSAUER, Tom. CLAYDEN, Graham. Illustrated textbook of Paediatrics. 3rd ed. London: Mosby Elsevier, 2007
  3. KIM YH, PARK HS, HYUN MC, KIM YN. Pediatric tachyarrhythmia and radiofrequency catheter ablation: results from 1993 to 2011. Korean Circ J [online]. 2012;42(11):735-40 [viewed on 20th April] Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518706/
  4. HAFEZ M, ABU-ELKHEIR M, SHOKIER M, AL-MARSAFAWY H, ABO-HADED H, EL-MAATY MA. Radiofrequency catheter ablation in children with supraventricular tachycardias: intermediate term follow up results. Clin Med Insights Cardiol [online]. 2012;6:7-16 [viewed on 20th April]. Available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256955/