Wed3November0844PM 15

A 68-year-old woman presents to the Emergency department with sudden onset palpitations. She had recently seen her GP with a productive cough and had been put on a course of antibiotics.

Past medical history consists of atrial fibrillation, hypertension, type 2 diabetes mellitus and anxiety. Drug history consists of warfarin 3 mg, digoxin 125 mcg, bisoprolol 2.5 mg, gliclazide 40 mg, diazepam 5 mg and erythromycin 500 mg.

An ECG shows sinus rhythm 80 bpm with a QTc of 500 milliseconds.

Which of her above medications is likely to be the cause of the prolonged QTc?

(Please select 1 option)

Erythromycin Correct

Bisoprolol

Digoxin

Diazepam

Gliclazide

Explanation

Long QT syndrome is associated with the potentially deadly rhythms torsades de pointes and ventricular fibrillation.

There are over 50 common prescribed medications known to prolong the QT interval. Antiarrhythmics are the most potent. These include common medications such as amiodarone and sotalol.

Antidepressants (tricyclics and SSRIs) and antipsychotics (haloperidol and phenothiazides) have been well documented to prolong the QT interval.

Other common classes of drugs that people with long QT syndrome should avoid include antibiotics such as macrolides and quinolones, as well as antiemetics such as ondansetron.