Arrhythmias

In a British study screening 3300 healthy asymptomatic infants, 1 % had arrhythmias detected on ECGs or Holter monitors. Most of these spontaneously resolved by 3 months of age. The most common symptomatic arrhythmia in infants is supraventricular tachycardia (SVT); 80% of cases occur in children less than 12 months of age, and 60% occur in the first 4 months of life. Ventricular tachycardia is much less common in infants and is usually associated with abnormal myocardium, congenital or acquired myopathies, long Q-T syndrome, or postsurgical scarring.

Causes

Problems can occur anywhere along this conduction system, causing various arrhythmias. Examples include:

• Supraventricular tachycardia - a fast heart rate that originates in the upper chambers (atria). The most common are atrial fibrillation or flutter, and atrioventricular nodal reentry tachycardia.
• Ventricular tachycardia - a fast heart rate that originates in the lower chambers (ventricles).
• Bradycardia - a slow heart rate due to problems with the SA node's pacemaker ability, or some interruption in conduction through the natural electrical pathways of the heart.

Symptoms

• Crying
• Irritability
• Poor feeding

Signs

• Irritability (possible early sign)
• Feeding intolerance (possible early sign)
• Tachycardia that is sustained can cause poor peripheral perfusion and CHF seen in the structural lesions noted above. Heart rates are in excess of 220, often 250 to 300.

Treatment

When an arrhythmia is serious, urgent treatment may be required to restore a normal rhythm. This may include intravenous medications, electrical "shock" therapy, or implanting a temporary pacemaker to interrupt the arrhythmia.

Arrhythmias may be treated with anti-arrhythmic drugs. But, most supraventricular arrhythmias can be treated and cured with radiofrequency ablation, eliminating the need for lifelong drug therapy.

Increasingly, wide ventricular tachycardias are treated with an implantable cardioverter-defibrillator (ICD). As soon as arrhythmia begins, the ICD sends a shock to terminate it, or a burst of pacing activity to override it.

Bradycardias that cause symptoms can be treated by implanting a permanent pacemaker.