Electrocardiographic Manifestations of Benzodiazepine Toxicity

Background: The aim of this study was to evaluate and compare the clinical and ‎electrocardiographic (ECG) manifestations of benzodiazepines (BZs).‎ Methods: In this retrospective study, all BZ-poisoned patients hospitalized at Loghman ‎Hakim Hospital between September 2010 and March 2011 were evaluated. Patients’ ‎information including age, sex, time elapsed between the ingestion and presentation, ‎and type of the BZ used were extracted from the patients' charts and recorded. ECGs ‎on presentation to the emergency department (ED) were evaluated and parameters ‎such as PR interval, QRS duration, corrected QT, amplitude of S wave in lead I, height ‎of R wave and R/S ratio in the lead aVR were also measured and recorded.‎ Results: Oxazepam, chlordiazepoxide, lorazepam, alprazolam, diazepam, and ‎clonazepam were ingested by 9 (3%), 13 (4.4%), 29 (9.9%), 105 (35.8%), 65 (22.2%), ‎and 72 (24.6%) patients, respectively. Mean PR interval was reported to be 0.16 ± 0.03 ‎sec and PR interval of greater than 200 msec was detected in 12 (4.5%) patients. Mean ‎QRS duration was 0.07 ± 0.01sec and QRS≥120 msec was observed in 7 (2.6%) ‎cases. ‎ Conclusion: Diazepam is the only BZ that does not cause QRS widening and ‎oxazepam is the only one not causing PR prolongation. It can be concluded that if a ‎patient refers with a decreased level of consciousness and accompanying signs of BZ ‎toxicity, QRS widening in ECG rules out diazepam, whereas PR prolongation rules out ‎oxazepam toxicity.‎