Traditional risk factors for QT interval prolongation and torsades de pointes

Risk factors are important for the development of torsades de pointes (TdP), and drug-induced TdP is extremely rare in the absence of risk factors. Traditional risk factors for QTc interval prolongation and TdP include acute myocardial infarction/ischemia, older age, anorexia/malnutrition, bradyarrhythmias, conversion from atrial fibrillation to sinus rhythm, elevated plasma concentrations of QT interval-prolonging drugs, female sex, heart failure with reduced ejection fraction, hepatic cirrhosis, electrolyte abnormalities (hypocalcemia, hypokalemia, and hypomagnesemia), hypothyroidism, history of TdP, possibly premature ventricular complexes, and prolongation of the QTc interval to ≥ 500 ms and/or > 60 ms from baseline (as a risk factor for TdP). Concomitant administration of multiple QT interval-prolonging drugs may be a risk factor for QTc prolongation and TdP, but not all studies support this concept, and whether a combination of QT interval-prolonging drugs increases the risk of QTc prolongation compared to that associated with individual QT-prolonging drugs alone likely depends on the specific drugs being combined. To minimize the risk of TdP, correctable risk factors should be ameliorated. In patients with non-modifiable risk factors who require therapy with a QT interval-prolonging medication, QTc interval-prolonging drugs should be used cautiously, and frequent QT interval monitoring should be implemented where feasible.