Prolonged QT: Causes & Drugs
Drugs whose administration risks converting aprolonged QTc to Torsades de pointes , including: The QT interval is measured from the start of the Q wave till the end of the T wave. The corrected QT interval is calculated using Bazett’s formula : QTc = (QT interval ) / √(RR Interval) A QTc of > 440 msec is considered prolonged. Causes: Medications (more than 75) that can lengthen the QT interval and upset heart rhythm include: Certain antibiotics Certain antidepressant and antipsychotic medications Some antihistamines Diuretics Medications used to maintain normal heart rhythms (antiarrhythmic medications) Cholesterol-lowering medications Certain diabetes medications