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.‎