Tricyclic antidepressant overdose and electrocardiographic changes

Abstract

A 39-year-old female with a history of intravenous drug abuse and depression was brought to the Emergency Department (ED) when she was found unresponsive at home. The respiratory rate was 4–5 breaths/min at home and the patient was given 2 mg. of naloxone intramuscularly. In the ED, the blood pressure was 120/70 mmHg, respiratory rate was 22 breaths/min, and pulse rate was about 190 beats/min. The patient was intubated in the ED. The rhythm monitor showed a short run of ventricular tachycardia. Lidocaine 120 mg intravenous bolus followed by continuous infusion was given. The first electrocardiogram (EKG-1) showed wide complex tachycardia with a rate of 210/min, prolonged corrected QT interval of 471 ms, and right-axis deviation (186°) of mean frontal plane QRS axis. The patient was given 6 mg and 12 mg Adenosine followed by a synchronized shock of 100 joules. The repeat electrocardiogram (EKG-2) showed atrial fibrillation with a ventricular rate of 146/min, wide complex aberrant beats, corrected QT interval of 570 ms, and right-axis deviation (174°) of mean frontal plane QRS axis. Meanwhile, the blood test showed a tricyclic antidepressant level of 357, and the urine tested positive for opiate and methadone. Intravenous sodium bicarbonate drip was started and the patient was admitted to the Critical Care Unit for monitoring. After 8 h, a repeat electrocardiogram (EKG-3) revealed normal sinus rhythm with a rate of 98/min, normalization of QT interval (391 ms), and normal QRS axis of 76°.