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Is there a relation between SIDS and long QT syndrome?
  1. J R Skinner
  1. Correspondence to:
    Dr J R Skinner
    Paediatric cardiologist/electrophysiologist, Starship Children’s Hospital, Park Road, Auckland, New Zealand;

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A discussion of the evidence to date

Long QT syndrome causes sudden unexpected death through rapid ventricular tachycardia (“torsades de pointes”) leading to ventricular fibrillation (see figs 1 and 2).1,2 The postmortem examination reveals no cause for the death. These characteristics make long QT syndrome a plausible cause of sudden infant death syndrome (SIDS), and many research efforts have been made to investigate a possible link. The genetic forms of long QT syndrome are usually inherited in an autosomal dominant fashion (Romano-Ward syndrome). Yet gene carriers can be asymptomatic, and around a third can even have a normal ECG.3 Therefore the condition might theoretically cause multiple SIDS within a family, with apparently healthy parents. It has been suggested that parents in such families might have been wrongfully accused of murder.4,5

Figure 1

 (A) This six lead rhythm strip from an infant with syndactyly and long QT syndrome shows gross prolongation of the QT interval. Two p waves are seen for each T wave. There is 2:1 atrioventricular block because the t wave has not even started when the next p wave appears; since ventricular repolarisation has not yet occurred, the ventricle cannot yet be depolarised again. This phenomenon has been reported in sudden infant death secondary to long-QT type 3.37 (B) This six lead rhythm strip was taken from the same infant as in (A), moments later. The QT interval is very long, and the t wave is alternately upright and then inverted. Repolarisation is disordered and swinging like a pendulum in one direction across the myocardium and then another. This typically precedes torsades de pointes.

Figure 2

 ECG strip recorded from an implanted digital loop recorder (Reveal device) during a syncopal episode from which recovery occurred spontaneously. Although taken from an 11 year old boy, this shows …

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  • Competing interests: none declared