Electrocardiographic changes from tricyclic antidepressant overdose

The QRS complex is prolonged with delayed right ventricular activation and intraventricular conduction delay, which results in rightward shift in the terminal 40 msec frontal plane QRS vector. In qualitative terms, this shift manifests as a deep, slurred S wave in leads I and AVL, and an R wave in lead AVR (blue arrows).