Arrhythmias in Adolescents

Arrhythmias in Adolescents

Arrhythmias in adolescents may vary from sinus arrhythmia which is a normal variant to life threatening arrhythmias like ventricular tachycardia. Wandering atrial pacemaker, isolated ventricular and supra ventricular ectopic beats and first degree AV block are some other arrhythmias which need no specific treatment. On the other hand, supraventricular tachycardia, ventricular tachycardia and symptomatic complete heart block definitely require treatment. Ventricular fibrillation calls for immediate cardiopulmonary resuscitation and defibrillation. Opinion is still divided regarding asymptomatic complete heart block with a narrow QRS complex and a good ventricular rate. Arrhythmias can occur in an otherwise quite healthy adolescent. Management of arrhythmias in adolescents is rather individualized on a case to case basis. The basic questions to be asked are whether there is associated structural heart disease and whether the arrhythmias are symptomatic. If the answer is yes to either one of these questions, the arrhythmia often requires treatment.

Sinus arrhythmia

Sinus arrhythmia is the most common irregularity of the heart rhythm and it is a normal variant. It is due to the interaction between the autonomic control of the respiration and the cardiac rhythm. Heart rate increases during inspiration and decreases during expiration. This is respiratory sinus arrhythmia which can be exaggerated in some cases.

Non respiratory varieties of sinus arrhythmias have also been described. One of these is the ventriculophasic sinus arrhythmia seen in complete heart block. PP interval enclosing a QRS complex is shorter in ventriculophasic sinus arrhythmia.

In sinus arrhythmia, the P waves, QRS complexes and T waves have normal morphology and relationships to each other. Only the PP interval varies.

Wandering atrial pacemaker

Wandering atrial pacemaker is also a normal variant. The pacemaker focus shifts from the SA node into the atrium and may go up to the AV node and then back again. The P wave morphologies vary continuously. As each focus has a different cycle length, this rhythm is irregular.

Isolated supraventricular ectopic beats

Isolated supraventricular premature complexes (SVPC) are benign in the absence of structural heart disease. In the presence of structural heart disease, they may indicate atrial dilatation, which could be a consequence of ventricular dysfunction. The P waves occur earlier than expected and have a different morphology from the sinus P wave. P wave originating from the lower part of the atrium are inverted in inferior leads as the activation front proceeds from below upwards, away from the inferior leads. The supraventricular ectopics can either be conducted normally or with aberrancy producing a wide QRS complex which may be mistaken for a ventricular premature complex. Sometimes the P waves may not be conducted (blocked atrial ectopic).

Ventricular premature complexes (VPC)

Isolated ventricular ectopic beats are premature wide QRS complexes, not preceded by a P wave and followed by a compensatory pause. ST segment and T waves are in opposite direction to the QRS complexes. Unifocal or monomorphic VPCs are the most common variety. VPCs may also occur in bigeminal or trigeminal pattern [1]. Couplets and salvos are rare and may indicate a more sinister problem. Monomorphic VPCs usually originate from the right ventricular outflow tract (LBBB pattern with inferior axis). Benign VPCs usually disappear with exercise, only to reappear during recovery. Only advice in case of benign VPCs is to avoid caffeine and other stimulants which can increase their frequency in some individuals.

First degree and second degree AV blocks

First degree AV block is manifested as a prolonged PR interval. It does not cause any bradycardia by itself. In second degree AV block, some P waves are not conducted so that bradycardia can occur, depending on the conduction ratio. Please note that the PR interval varies with the age and heart rate. First degree heart block may be seen in rheumatic fever, rubella, mumps, hypothermia, cardiomyopathies and electrolyte disturbances. Second degree AV block can by type I or type II, depending on whether there is progressive prolongation of PR interval or not. If two or more sequential P waves are not conducted, it is called advanced AV block.

Complete heart block or third degree AV block

Complete AV block is characterized by total dissociation between the P waves and QRS complexes. The P waves and QRS complexes are regular, but the PP interval is shorter than the RR interval and the PR interval is totally varying. Complete heart block can be congenital or acquired. Congenital complete heart block is associated with maternal connective tissue diseases like systemic lupus erythematosus (SLE). Corrected transposition of great arteries is also associated with congenital complete heart block. Congenital complete heart block is often asymptomatic and missed clinically. High risk group in complete heart block includes those with a slower heart rate and wide QRS escape rhythm. A pacemaker is needed if complete heart block is associated with syncope, exercise intolerance, ventricular arrhythmias or structural heart disease. Since there is a gradual attrition rate for congenital complete heart block some authorities are considering pacemaker implantation even in the asymptomatic group.

Supraventricular tachycardia (SVT)

Supraventricular tachycardia is the most common abnormal tachycardia in adolescents. It is also the most common arrhythmia requiring treatment. It is regular and usually associated with a narrow QRS complex. A supraventricular tachycardia with aberrancy or in the presence of an accessory pathway conducting anterograde, it is often mistaken for a ventricular tachycardia. Supraventricular tachycardias are paroxysmal with sudden onset and offset.

The tachycardia rates may vary between 180 – 250 /min in adolescents. The rates may be higher in younger age group. P waves are often difficult to decipher in SVT, but the QRS response is 1:1. An important differential diagnosis is sinus tachycardia which is occasionally mistaken for SVT. Treatment with vagal maneuvers may be tried in stable patients. Others are given weight adjusted intravenous adenosine bolus. ECG and blood pressure are continuously monitored during therapy. Synchronized cardioversion and amiodarone are the other options. Trans esophageal pacing is another modality of treatment which is seldom done now a days. A post conversion ECG is mandatory, which may sometimes demonstrate pre-excitation. An echocardiogram may be needed to exclude structural heart disease. Radio frequency catheter ablation is a curative option, sometimes needed in adolescents. Drugs like digoxin, betablockers, verapamil and amiodarone have been used in maintenance therapy for prevention of episodes.

Other forms of supraventricular tachycardias

Other forms of supraventricular tachycardias are less common in adolescents. They include atrial flutter / fibrillation, ectopic atrial tachycardias and junctional tachycardias. Adenosine does not terminate those rhythms which originate above the AV node. The treatment options include amiodarone, cardioversion and catheter ablation.

Ventricular tachycardia

Sustained ventricular tachycardias are uncommon in adolescents and definitely needs full work up [1]. They are regular wide QRS tachycardias with AV dissociation. Ventricular tachycardia is a potentially life threatening arrhythmia and is often associated with open heart surgery, cardiomyopathies, myocarditis and tumors. As the number of palliated congenital heart disease patients increase, the number with ventricular tachycardia related to ventricular scars can also increase. Immediate treatment of ventricular tachycardia is with either intravenous lignocaine or amiodarone. In a critically ill person immediate synchronized cardioversion is resorted to. Long term treatment options include medications like betablockers and amiodarone or catheter ablation / implantation of an implantable cardioverter defibrillator.

One rare but interesting form of ventricular tachycardia is the catecholaminergic polymorphic ventricular tachycardia (CPVT) which present with tachycardia related to exercise or emotional stress. It is a genetically mediated condition due to abnormalities in either cardiac ryanodine receptors or calsequestrin [2].

Ventricular fibrillation

Ventricular fibrillation is ominous and needs immediate cardiopulmonary resuscitation and defibrillation for survival. Ventricular fibrillation can be due to long QT syndromes, Brugada syndromes, cardiomyopathies, CPVT or any form of structural heart disease with ventricular dysfunction.

Sudden cardiac arrest

Sudden cardiac arrest can occur in 0.6 to 6.2 per 100 000 children per year in the United States [3]. The important causes include hypertrophic cardiomyopathy, long QT syndrome, coronary anomalies and WPW syndrome. Cardiac arrest due to toxins and drugs should also be thought of in an appropriate situation.

References

1. Friedli B. Ventricular arrhythmias in children and adolescents. Pediatrician. 1986;13(4):189-98.
2. Francis J, Sankar V, Nair VK, Priori SG. Catecholaminergic polymorphic ventricular tachycardia. Heart Rhythm. 2005 May;2(5):550-4.
3. Gajewski KK, Saul JP. Sudden cardiac death in children and adolescents (excluding Sudden Infant Death Syndrome). Ann Pediatr Cardiol. 2010 Jul;3(2):107-12.