long QT

Long QT syndrome is among the most common inherited arrhythmias, affecting between 1 in 1000 and 1 in 5000 persons. Prolongation of the QTc interval has many causes, most of which are acquired, such as medication use, structural heart disease, and electrolyte abnormalities. Drugs that have been implicated in QT prolongation include antiarrhythmic agents, antibiotics (including some macrolides and fluoroquinolones), antipsychotic drugs, and antidepressants. A list of drugs categorized by their potential to cause QT prolongation is available at https://crediblemeds.org. The presence of a prolonged QTc interval (>440 ms in men and >460 ms in women) alone is insufficient to diagnose long QT syndrome. Diagnosis requires the presence of a QTc interval greater than 500 ms on repeated 12-lead ECGs accompanied by unexplained syncope or ventricular arrhythmia. Patients with a QTc interval greater than 500 ms are at greatest risk for SCD. β-Blockers are first-line therapy; however, patients with cardiac arrest or those who have recurrent events (syncope or VT) refractory to β-blocker therapy are candidates for ICD placement. These patients should not participate in competitive athletics.