[Congenital long QT syndrome]

Risque cardiovasculaire des antipsychotiques, une surveillance nécessaire de l’intervalle QT

Torsades de pointes (TdP), a form of ventricular arrhythmia that can cause ventricular fibrillation and sudden death, may occur during prolongation of the QT interval. QT prolongation has recently been reported with antipsychotic drugs. Physicians should be able to obtain a corrected measurement of the QT interval. QT is measured from the beginning of the QRS complex to the end of the T wave (QTm). This value must then be corrected to take heartbeat into account. The most common formula in current use is Bazett's. In practice, a QTc interval value greater than 500 ms indicates an increased risk of TdP. Safe combinations of antipsychotic drugs have been recommended by the French drug agency (Agence française de sécurité sanitaire des produits de santé). Many other drugs, including psychotropic drugs such as tricyclic antidepressants, can prolong the QT interval. Combinations of these medications with one another, with antipsychotic medications, or with other concomitant factors, such as hypokalemia, also increase the risk. TdP is most often diagnosed only after observing QT prolongation. This underlines the need to monitor QT intervals attentively to prevent the risk of cardiac arrhythmia in patients treated with antipsychotic drugs.

[Andersen syndrome, ventricular arrhythmias and channelopathy (a case report)]

INTRODUCTION

Recent advances in molecular genetic research have provided new insights into severe ventricular arrhythmias related to channelopathies.

CASE REPORT

A case of Andersen's syndrome followed during fourteen years is reported. This rare familial periodic paralysis is characterized by its association with dysmorphic features (micrognatia) and ventricular arrhythmias.

COMMENTS

Andersen's syndrome has been attributed to a mutation in the KCNJ2 gene which is involved not only in stabilizing cardiac rhythm, but also in modulating the excitability of skeletal muscle and in morphogenesis. This disease must be distinguished from hyperkalemic periodic paralysis due to a mutation in the skeletal muscle sodium channel gene (SCN4A) and from hypokalemic periodic paralysis related to dihydropyridine receptor mutation (CACNL1A3). Furthermore, it may not be confused with others rhythmic channelopathies (long QT syndromes, catecholaminergic polymorphic ventricular tachycardia and Brugada's syndrome).