SeminarLong QT syndromes and torsade de pointes
Section snippets
Acute identification of torsade de pointes
Two electrocardiographic features of torsade de pointes that help to establish a diagnosis are its typical mode of onset and its morphology.
Almost all arrhythmias caused by an acquired LQTS,24, 25 and most arrhythmias caused by congenital LQTS (at least in adults),26, 27 are preceded by pauses (figure 2). The pauses that lead to torsade de pointes may be due to sinus arrhythmia or sinus arrest. More commonly, these are “post-extrasystolic pauses”24, 25, 26 (figure 2). In a typical escalating
Emergency therapy for torsade de pointes
Torsade de pointes that degenerates to ventricular fibrillation requires DC shock for termination. However, torsade de pointes is not sustained in most cases, and even prolonged arrhythmias may terminate spontaneously. Since the stress caused by DC shocks may trigger recurrent arrhythmias, shock delivery should be withheld until the patient loses consciousness or is sedated. More challenging is the prevention of immediate recurrence of torsade de pointes. Urgent measures include: removal of any
Long-term management of congenital LQTS
Two forms of familial LQTS have long been known: the Jervell and Lange-Nielsen syndrome (with congenital deafness and malignant arrhythmias in infancy); and the Romano-Ward syndrome (with normal hearing and autosomal-dominant inheritance). The first form is very rare. Hence, gene mutations were first identified for families with normal hearing. In the Jervell-Lange-Nielsen syndrome the cardiac malfunction (involving IKs channels) is of autosomal-dominant inheritance, whereas deafness is
Bradyarrhythmia-induced torsade de pointes
The slower the heart rate, the longer the repolarisation will be. Even short-lasting bradycardia, such as that caused by adenosine injection, may rarely culminate in torsade de pointes.49 However, bradyarrhythmia-induced torsade de pointes is primarily seen during complete atrioventricular block. Additional risk factors (panel 3) increase the risk of torsade de pointes during bradyarrhythmias. Hypokalaemia must be prevented in patients with bradyarrhythmias. Nevertheless, the most important
Is acquired LQTS really “acquired”?
Several lines of evidence suggest that patients with acquired LQTS have some underlying predisposition to proarrhythmia. The QT measured before drug exposure tends to be longer in patients who eventually develop drug-induced torsade de pointes than in patients who receive the same drug safely.20, 21, 70 Patients with drug-induced torsade de pointes are at high risk of recurrent arrhythmias if exposed to a second antiarrhythmic drug.21 Among patients with heart block, the QT interval (rather
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