Prolonged QT Interval in Methadone Poisoning: A ۱۰-Year Retrospective Study of ۱,۰۰۰ Cases

Background: Methadone overdose is increasingly recognized as a cause of acquired long‑QT syndrome and life‑threatening ventricular arrhythmias, yet the prevalence and clinical correlates of QT prolongation in poisoned patients remain incompletely characterized. Objectives: This study aimed to determine the frequency of QT interval prolongation in patients with methadone poisoning and to identify clinical factors associated with prolonged QT in this population. Methods: In this retrospective observational study, we reviewed ۱,۰۰۰ consecutive patients admitted to Shah Vali (Yazd City, Iran) and Shahid Beheshti (Taft City, Iran) hospitals for methadone overdose between January ۲۰۱۴ and December ۲۰۲۳. Demographic characteristics, reported methadone dose, comorbid cardiovascular diseases, electrolyte profiles, and electrocardiographic (ECG) measurements were extracted from medical records. QT intervals were obtained from the initial ۱۲-lead ECG at admission and categorized as normal/borderline (<۴۵۰ ms) or prolonged (≥۴۵۰ ms). Associations between prolonged QT and age group (<۴۵ vs ≥۴۵ years), sex, comorbidity, electrolyte disturbances, and arrhythmias were assessed using chi‑square tests and crude odds ratios (OR). Results: The mean age was ۳۲.۸±۹.۶ years, and the mean reported methadone dose was ۷۵.۴±۲.۲۵ mg. The mean QT interval was ۴۷۸.۶±۳۲.۱ ms, and QT prolongation (≥۴۵۰ ms) was observed in ۴۸.۰% (n=۴۸۰) of patients. Prolonged QT was significantly associated with younger age (P=۰.۰۲), female sex (P=۰.۰۵), cardiovascular comorbidity (P=۰.۰۲), and electrolyte imbalances, particularly hypokalemia (P=۰.۰۲). Patients with prolonged QT also had a higher frequency of clinically documented arrhythmias, including torsades de Pointes (TdP) (P=۰.۰۰۲). Conclusion: QT interval prolongation is common among hospitalized patients with methadone poisoning and is strongly associated with younger age, female sex, cardiovascular disease, electrolyte abnormalities, and malignant arrhythmias. These findings support routine ۱۲‑lead ECG screening, continuous cardiac monitoring, and prompt correction of electrolyte disturbances in all patients presenting with methadone overdose.

کلیدواژه ها:

Methadone ، Poisoning ، Electrocardiography (ECG) ، Long QT syndrome ، Cardiotoxicity ، Opioid-related disorders