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.