Acquired long QT syndrome: risperidone-facilitated triggered activity and Torsades de Pointes during complete AV block. I.
The acquired Long QT Syndrome (aLQTS) is attributed to subtle defects in genes encoding potassium currents (Ik) that may become clinically significant when associated with other factors that impair ventricular repolarization, such as female gender, bradycardia, hypokalemia or the administration of ion channel blocking drugs. We describe full exposure of an aLQTS in a elderly female patient on long-term Risperidone treatment just when bradycardia due to complete AV block developed. We postulate that the aLQTS induced is the result of a combined block of the rapid (I(Kr))and delayed (I(Ks)) components of the Ik current. The electrocardiographic manifestation of (likely) phase 2 early afterdepolarizations and a critical transmural dispersion of repolarization (TDR), both required for the initiation and maintenance of the polymorphic ventricular tachycardia associated with the syndrome (Torsades de Pointes), are as well shown. Risperidone should be used with caution in female patients prone to bradycardia.