Podcast 855: QT Intervals

<p dir="ltr"><strong>​​Contributor:</strong> Travis Barlock MD</p> <p dir="ltr"><strong>Educational Pearls</strong></p> <ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">The QT interval represents phases 2 and 3 of ventricular plateau and repolarization, respectively.</p> </li> <ul> <li dir="ltr" aria-level="2"> <p dir="ltr" role="presentation">As the QT interval lengthens, more sodium and calcium channels are available and susceptible to action potentials.</p> </li> </ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Prolonged QT interval is more concerning in the setting of bradycardia.</p> </li> <ul> <li dir="ltr" aria-level="2"> <p dir="ltr" role="presentation">This scenario increases the likelihood of R on T phenomenon. </p> </li> </ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">R on T phenomenon occurs due to an early afterdepolarization event in which a premature ventricular contraction (PVC) occurs during the repolarization period (superimposed on the T wave), leading to an aberrant re-entry circuit.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">The re-entry circuit leads to Torsades de Pointes (polymorphic ventricular tachycardia with prolonged QT) and subsequent ventricular fibrillation.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">Treatment for Torsades de Pointes is 2g MgSO4.</p> </li> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">The preferred antiarrhythmic for VTach is IV lidocaine 1.5 mg/kg over 2 minutes.</p> </li> <ul> <li dir="ltr" aria-level="2"> <p dir="ltr" role="presentation">Avoid amiodarone due to risk of further QT prolongation.</p> </li> </ul> <li dir="ltr" aria-level="1"> <p dir="ltr" role="presentation">A heart rate under 80 does not need QT correction</p> </li> <ul> <li dir="ltr" aria-level="2"> <p dir="ltr" role="presentation">Corrected QT interval is used in the setting of tachycardia due to an abnormally small T wave</p> </li> </ul> <li dir="ltr" aria-leve