• psychiatry
• clinical physiology
• clinical pharmacology
• cardiology

In our day-to-day clinical practice, most of the emphasis is placed on QTc prolongation because psychotropic drugs that we commonly prescribe are known to cause this. However, a short QTc interval is equally important to be mindful of when prescribing or monitoring patients’ ECGs.

We conducted a literature search in September and October 2019, using PubMed. Studies were included if they described psychotropics effects on QTc interval. Keywords used were QTc, psychotropics ECG.

Why does the QTc matter to us as psychiatrists? The short answer is that all medications at the dispense of a psychiatrist have some serious cardiotoxic side effects. This can pose as a challenge because we often see patients with significant cardiac comorbidities and polypharmacy, which can be aggravated by use of cardiotoxic medication.

Antipsychotics: Antipsychotic drugs have long been known to be associated with risk of cardiac arrhythmia and cardiac arrest. These arrhythmias are often reflected as changes in the ECG, prolongation of the QT interval, ventricular tachycardias and torsades de pointes (TdP). TdP is a potentially life-threatening ventricular tachyarrhythmia that is associated with syncope and sudden death.1 Such effects could be antiarrhythmic or cardiotoxic, depending on the health (eg, post-myocardial infarct) of the myocardium.

Antidepressants: The cardiovascular toxicity of older generation of tricyclic antidepressants (eg, imipramine, desipramine, amitriptyline, clomipramine) and neuroleptics (eg, haloperidol, droperidol, thioridazine, pimozide) is well established. These drugs inhibit cardiovascular Na⁺, Ca²⁺ and K⁺ channels often leading to life-threatening arrhythmia.1

Mood stabilisers: Lithium is a commonly used mood stabiliser, associated with cardiac side effects of ventricular irritability, sinus node dysfunction, benign, reversible T wave changes (including inversion and flattening). Carbamazepine has quinidine-like effects and can aggravate heart block.2

When talking about factors affecting the QTc, a short QTc syndrome is an …