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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 3, May/June 2015
AFRICA
145
who develop QT prolongation and TdP have an underlying
genetic predisposition, resulting in prolongation of the action
potential duration, which is exacerbated by the bradycardia.
Conclusion
Our case re-emphasises the risks involved in administering
erythromycin to patients. In particular, patients with AV block
should not receive this drug. The timing of the TdP is interesting
because it coincided with the insertion of the temporary pacing
lead. It is very likely that the ventricular ectopics induced by
the temporary lead in the right ventricular apex precipitated the
short–long cycle that led to the TdP. Instead of repeated DC
cardioversion, we could have temporarily paced the patient at
a more rapid rate to prevent the recurrence of the bradycardia-
induced TdP. Based on data from Kurita
et al.
,
9
a rate above 60
bpm would have been sufficient to prevent further episodes of
TdP.
References
1.
Strasberg B, Kusniec J, Erdman S, Lewin RRF, Arditti A, Sclarovsky S,
et al
. Polymorphous ventricular tachycardia and atrioventricular block.
PACE
1986;
9
: 522–526.
2.
Ziegenbein M, Kropp S. Lorazepam-induced prolongation of the QT
interval in a patient with schizoaffective disorder and complete AV
block.
Can J Psychiatry
2004;
49
: 414.
3.
Ginwalla M, Biblo LA, Paydak H. Torsade de Pointes following intrave-
nous haloperidol administration in a patient with complete heart block.
Wisconsin Med J
2009;
108
: 48–50.
4.
Bazett HC. An analysis of the time-relations of electrocardiograms.
Heart
1920;
7
: 353–370.
5.
McComb JM, Campbell NPS, Cleland J. Recurrent ventricular tachy-
cardia associated with QT prolongation after mitral valve replacement
and its association with intravenous administration of erythromycin.
Am J Cardiol
1984;
54
: 922–923.
6.
Rubart M, Pressler ML, Pride HP, Zipes DP. Electrophysiological mech-
anisms in a canine model of erythromycin-associated log QT syndrome.
Circulation
1993;
88
: 1832–1844.
7.
Antzelevitch C, Sun Z-Q, Zhang Z-Q, Yan G-X. Cellular and ionic
mechanism underlying erythromycin-induced long QT intervals and
Torsade de Pointes.
J Am Coll Cardiol
1996;
28
: 1836–1848.
8.
Daleau P, Lessard E, Groleau M-F, Turgeon J. Erythromycin blocks
the rapid component of the delayed rectifier potassium current and
lengthens repolarization of guinea pig ventricular myocytes.
Circulation
1995;
91
: 3010–3016.
9.
Kurita T, Ohe T, Marui N, Aihara N, Takaki H, Kamakura S,
et
al
. Bradycardia-induced abnormal QT prolongation in patients with
complete atrioventricular block with Torsade de Pointes.
Am J Cardiol
1992;
69
: 628–633.