Prolonged Qt Syndrome

QT interval prolongation on the standard 12-lead ECG is the hallmark of a heterogeneous group of disorders characterized by malignant ventricular arrhythmias (typically torsades de pointes) and a high incidence of syncope and sudden cardiac death (Fig. 4). Although congenital long QT syndrome (LQTS) was originally reported in children as a genetically transmitted disorder, acquired forms of LQTS have also been described. The pathogenesis of the arrhythmias associated with QT prolongation is incompletely understood, but sympathetic activation and early afterpotentials seem to be involved.

Initial therapy for the congenital LQTS characteristically involves beta-blockers. Other therapeutic modalities include left cervical sympathetic denervation, permanent pacing, and, in cardiac arrest survivors, implantable cardioverter defibrillators (ICDs). Presumably, permanent pacing exerts its beneficial effects by preventing pauses that initiate episodes of torsades, by shortening repolarization and decreasing dispersion of refractoriness, and by eliminating, or diminishing the amplitude of, early afterpotentials. Several studies have found that permanent pacing may be effective in reducing the incidence of syncope in individuals with the LQTS (54-56). However, until mortality benefit has been demonstrated, permanent pacing should be considered to be no more than adjunctive therapy in this syndrome. The 1998 guidelines consider pause-dependent ventricular arrhythmias, with or without LQTS, a class I indication for pacing (1). However, many electrophysiologists presently consider an ICD a more appropriate therapy in high-risk patients with congenital LQTS. Pacing may reduce the risk of torsades in patients treated with QT-prolonging drugs and a tendency to bradycardia. In patients with excessive QT prolongation or torsades, the offending agent should be discontinued.

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Responses

  • aurelio
    Is a fibrillation a qt interval disorder?
    6 years ago

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