Cardiovascular Journal of Africa: Vol 26 No 3 (May/June 2015)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 3, May/June 2015 AFRICA 143
Case Report
An antibiotic recipe for an arrhythmic disaster
Keir McCutcheon, Pravin Manga
Abstract
We describe the case of a patient who developed torsade de
pointes during temporary pacemaker insertion after adminis-
tration of intravenous erythromycin. The case highlights the
dangers of administering drugs that prolong the QT interval
in patients with complete atrioventricular block, and we
discuss the underlying pathophysiological recipe that can lead
to a potential arrhythmic disaster.
Keywords: erythromycin, QT prolongation, complete heart
block, pacing, torsade de pointes
Submitted 10/7/13, accepted 11/1/15
Cardiovasc J Afr 2015; 26: 143–145
DOI: 10.5830/CVJA-2015-006
Torsade de pointes (TdP), a polymorphic ventricular tachycardia
caused by dispersion of depolarisation within the ventricles, is
an important complication of atrioventricular (AV) conduction
disorders.1 Various classes of drugs including antimicrobials, anti-
arrhythmic and psychotropic drugs may lead to prolongation
of the QT interval with an increased risk of TdP, especially in
patients with other risk factors for QT prolongation. However,
to date, there have been very few reports of TdP due to drugs in
patients with AV block,2,3 and, to our knowledge, no case reports
highlighting the hazard of using erythromycin in patients with
complete AV block.
The QT interval, which shortens during tachycardia and
lengthens during bradycardia, is the most useful measure to
predict a patient’s risk of developing TdP and several formulae
are available to correct for heart rate, the commonest being
Bazzet’s formula.4 Women normally have slightly longer QT
intervals than men.
We describe here a case of TdP during pacemaker implantation
after erythromycin administration. The case highlights the
potentially life-threatening effects of prescribing QT-prolonging
drugs in patients with severe bradyarrhythmias.
Case report
A 68-year-old woman, with a background of hypertension
controlled on medical therapy, presented with vague symptoms
of fatigue and poor exercise tolerance. She had no history
of antibiotic, anti-arrhythmic or psychotropic drug use in
the previous month. She had no history or family history of
syncope or sudden cardiac death and had no other significant
past medical history. However, she reported having an allergy to
penicillin.
The examination was unremarkable. Resting ECG showed a
sinus rhythm at 100 beats per minute (bpm) with complete AV
block and a ventricular escape at 33 bpm (Fig. 1, top strip). She
was haemodynamically stable and was booked for permanent
pacemaker implantation the following day.
At the time of pacemaker implantation, it is usual protocol
to give our patients prophylactic antibiotics during and after the
procedure. Most patients receive a first-generation cephalosporin
in three intravenous doses. However, because this patient had
reported an allergy to penicillin, it was decided that an alternative
antibiotic be used.
While the patient was being draped for the procedure, a single
dose of intravenous erythromycin 500 mg was infused. This was
followed by insertion of a transvenous temporary pacing lead
via the right femoral vein. The introduction of the transvenous
lead into the right ventricle resulted in right ventricular ectopic
beats during positioning in the right ventricle, and this resulted
in the induction of polymorphic ventricular tachycardia (Fig. 1,
middle strip), which required three rounds of DC cardioversion
at 200 J over a period of approximately 15 minutes. This restored
her to her baseline rhythm (Fig. 1, bottom strip). The patient
was transferred back to the coronary care unit where she was
given intravenous magnesium and, fortunately, the ventricular
tachycardia did not recur.
Cardiac catheterisation performed the following day revealed
normal coronary arteries and blood results showed no electrolyte
abnormality. Pacemaker implantation was subsequently
performed without antibiotic cover and with no further episodes
of TdP.
Discussion
We present a case of TdP due to QT prolongation in a patient
with complete AV block who received erythromycin. The patient
was not on any other medication known to prolong the QT
interval and her serum electrolyte levels were normal. The
arrhythmia occurred during insertion of a temporary pacing
lead and was treated emergently with electrical cardioversion.
Permanent pacemaker implantation for complete AV block is
a common cardiac procedure. Numerous drugs are administered
Division of Cardiology, Department of Medicine, University
of the Witwatersrand, and Charlotte Maxeke Academic
Hospital, Johannesburg, South Africa
Keir McCutcheon, BSc (Hons), MSc, MB BCh, FCP (SA), Cert
Cardiol (SA),
Pravin Manga, MB BCh, FCP (SA), PhD, FRCP (UK)