Long QT Syndromes.

Abstract

The clinical phenotype of the long QT syndrome (LQTS) is quite variable, with the frequency and type of life-threatening arrhythmias influenced by the specific genotype and a spectrum of genetic and environmental factors that are not well characterized. Patients with a history of recurrent syncope or aborted cardiac arrest are at increased risk of experiencing malignant ventricular arrhythmias, but such arrhythmias may also occur in affected individuals who previously have been asymptomatic. Beta-adrenergic drugs serve as the foundation for treatment of symptomatic patients with a history of syncope or aborted cardiac arrest and as primary prophylactic therapy in asymptomatic subjects with LQTS. Beta-blockers reduce the frequency of syncopal events, but they do not absolutely prevent the occurrence of sudden cardiac death, even in those who are compliant in taking full doses of beta-blockers. Pacemaker therapy is moderately effective in reducing the number of cardiac events in patients with inappropriate bradycardia. The implantable cardioverter-defibrillator (ICD) has functioned well as a fail-safe back-up therapy in high-risk patients, especially those with documented malignant arrhythmias or an aborted cardiac arrest. Left cervicothoracic sympathetic ganglionectomy should be reserved for patients with LQTS who are intolerant of beta-blockers or have recurrent syncope that is refractory to beta-blockers and who for one reason or another are not candidates for ICD therapy. Pharmacologically tailored gene-specific therapy for specific ion-channel disorders is in its infancy, and no specific recommendations can be made for the use of this therapy at this time.