A 25 Year Old Female With A History Of Depression Presents With An Overdose

A 25 year old female who was diagnosed with depression attempted suicide by taking an over doses of her prescription medicines clonazepam and nortriptyline. When seen in the emergency department, patient is unresponsive and is having difficulty in breathing. After the initial steps of incubating the patient and protection her airway an ECG was performed and the following was obtained:

The ECG shown above is showing torse de pointes.

Torsade de Pointes (TdP) is a form of polymorphic ventricular tachycardia associated with a long QT interval on the resting ECG. Torsade de Pointes is typically initiated by a short-long-short interval. A ventricle extrasystole (first beat: short) is followed by a compensatory pause. The following beat (second beat: long) has a longer QT interval. If the next beat follows shortly thereafter, there is a good chance that this third beat falls within the QT interval, resulting in the R on T phenomenon and subsequent Torsades de Pointes. During Torsades de Pointes the ventricles depolarize in a circular fashion resulting in QRS complexes with a continuously turning heart axis around the baseline (hence the name Torsade de Pointes).

Question:

What is the best treatment option for a patient with this type of arrhythmia secondary to tricyclic over dose?

Answer:
The treatment of choice for arrhythmia's in patients with a tricyclic overdose is sodium bicarbonate. Raising the pH and administering sodium seem to “prime” the sodium channels in the heart reversing the toxicity of the tricyclic.