Title: Background information

Context:
QTc interval >450 ms for using methadone: Unlike most other commonly used opioids, methadone has unique pharmacodynamic properties that can prolong the QTc interval (the heart rate’s corrected time interval from the start of the Q wave to the end of the T wave) and precipitate torsades de pointes, a dangerous or fatal cardiac arrhythmia. Patients who may be at risk include those with other risk factors for QTc prolongation, current or prior electrocardiograms (ECGs) with a prolonged QTc >450 ms, or a history of syncope. Therefore, ECGs before and after initiating methadone are highly advised (see Methadone Dosing Guidance).

Question: What is QTc interval?

Answer: the heart rate’s corrected time interval from the start of the Q wave to the end of the T wave