Sinus tachycardia is present in most patients with clinically significant tricyclic antidepressant (TCA) overdose. Delayed right ventricular activation from TCA intoxication results in a deep, slurred S wave in leads I and aVL as well as an R wave in lead aVR, as seen in Figure 2. A cohort study showed that the risk of seizures and ventricular arrhythmias was significantly increased in patients with RaVR greater than 3 mm and QRS duration longer than 100 msec.2 A prolonged QTc interval and PR interval are also seen in TCA intoxication but are much less reliable for confirming the diagnosis. Esomeprazole is well tolerated except for diarrhea. There are no known cardiovascular or neurologic side effects associated with esomeprazole, and no deaths have been reported. Large doses of gabapentin typically produce central nervous system depression (eg, drowsiness, dizziness, lethargy) as well as diarrhea but do not cause cardiovascular problems. An overdose of gemfibrozil results in gastrointestinal and musculoskeletal complaints with elevated liver function tests and creatine kinase levels. Patients who overdose on narcotics generally present with pinpoint pupils and respiratory depression, which can lead to bradycardia and ultimately pulseless electrical activity if respiratory drive is not addressed.
2. Liebelt EL, Francis PD, Woolf AD. ECG lead aVR versus QRS interval in predicting seizures and arrhythmias in acute tricyclic antidepressant toxicity. Ann Emerg Med 1995;26:195-201.
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