Supraventricular Tachycardia

Abstract

In young people, premature atrial contractions (PACs) can be frequent. Sometimes they are not transmitted to the ventricles or are conducted with aberrancy and therefore appear in the ECG with a wide QRS. PACs are normally a benign situation except when they trigger a reentry tachycardia. We should keep the number 220 in mind, quite an electrical number (220 V is the domestic voltage in most countries), as an upper limit for a sinus tachycardia. The reentry form is the most frequent mechanism of supraventricular tachycardia (SVT) in all ages. When SVT is diagnosed during fetal life, antiarrhythmic drugs are given to the mother in order to delay delivery. Atrial flutter is known as a typical fetal and newborn arrhythmia that could be fatal if misunderstood but which is extremely docile once treated with current synchronized cardioversion, with a low recurrence risk. In newborns, SVT is normally caused by an accessory pathway and is conducted between 250–300 bpm, while in children older than 6 years, nodal reentry SVT could appear with a frequency around 200 bpm (Fig. 11.1) [1]. The diagnosis of SVT in an infant is not easy inasmuch as it is frequently confounded with sepsis, heart failure, and decompensated ductus-dependent congenital heart diseases (i.e., aortic coarctation). In addition to its therapeutic efficacy, adenosine plays a diagnostic role, which is why it is named diagnosine, since adenosine makes it possible to discriminate between tachycardia depending on the atrioventricular node (AV node) and tachycardia not depending on the AV node including ventricular tachycardia (VT). Since atrial fibrillation (AF) is uncommon in the pediatric population, this means that adenosine is safe even in preexcitation syndromes (Fig. 11.2). A particularly unique arrhythmia is Coumel’s tachycardia (also known as permanent junctional reciprocating tachycardia (PJRT), an inappropriate definition because it is not a junctional tachycardia but an AV orthodromic reentry due to a slow conducting para junctional accessory pathway), treacherous for its heart rate, not that fast, that could be interpreted as normal in a routine clinical evaluation, but nevertheless capable of causing tachycardiomyopathy if not discovered and treated [2]. Automatic SVT, including incessant SVT, can appear at any age sometimes after flu or surgical procedures. Multifocal atrial tachycardia is typical during acute viral bronchiolitis (especially associated with respiratory syncytial virus) or during Costello syndrome [3].