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Figure 1: Electrocardiogram depicts a rhythm strip recorded from leads Figure 2: Electrocardiogram depicts a rhythm strip recorded from leads
V1‑V6 (10 s) with three premature ventricular contractures (PVCs). The heart V1‑V6 (10 s) without premature ventricular contractures (PVCs). The study
rate was 72 beats/min. The study was performed on April 8, 2009. This EKG was performed on April 14, 2009 and revealed normal sinus rhythm with the
was done on the next day after a single IFN‑beta‑1a injection (11 μg SC). Two heart rate 71 beats/min. This EKG was done 7 days after a single IFN‑beta‑1a
additional rhythm strips (10 s each) revealed 5 more PVCs (not shown) injection (11 μg SC). Two additional rhythm strips (10 s each) revealed no PVCs
as well (not shown)
after IFN-beta-1a injection. The repeat ECG on April
14, 2009 revealed normal sinus rhythm [Figure 2]. Although the IFN-alpha subtypes and IFN-beta interact
The patient was evaluated by a cardiologist. It was with a common receptor, IFN-alpha receptor (IFNAR),
concluded that cardiac arrhythmia with PVCs was which comprises high-affinity (IFNAR2) and
secondary to IFN-beta-1a treatment. The patient was low-affinity (IFNAR1) components, they nevertheless
switched to another (non-IFN-based) DMT for MS exhibit functional differences. [10] One may suggest
and has had no cardiac symptoms in the subsequent that difference in ligand-receptor affinity is one of
5 years. the possible explanations for these variations. Even
within the IFN-alpha species, individual subtypes
DISCUSSION may differ by over 10,000 fold in their biological
activity. [11] Recently, it was shown that IFN-beta binds
We describe cardiac arrhythmia with PVCs in a to IFNAR1 independently of IFNAR2. [12] Therefore, it is
22-year-old MS patient who received her first dose of not surprising that the induction of cardiac arrhythmia
IFN-beta-1a. The medication had been in her system may be less frequent in IFN-beta-treated compared with
for 3 h by the time the patient started experiencing IFN-alpha-treated patients. However, more studies need
palpitations, and it took 4 days for symptoms to resolve. to be done to understand the cause and prevalence
The pharmacokinetics of Rebif (IFN-beta-1a) in people of cardiac arrhythmia symptoms in IFN-beta- and
®
with MS has not been evaluated. In healthy volunteer IFN-alpha-treated patients. Nevertheless, as IFN-beta is
subjects, a single subcutaneous injection of 60 μg one of the most prescribed DMT for MS, the knowledge
of Rebif , resulted in a peak serum concentration of about this adverse effect is deemed to be important for
®
IFN-beta in approximately 16 h. The mean serum neurologists treating MS patients.
elimination half-life was 69 h. There were no previously
[5]
described cases of early onset cardiac arrhythmia in ACKNOWLEDGMENTS
IFN-beta-treated patients. Kastalli et al. reported a case
of cardiac arrhythmia in a 35-year-old MS patient who We would like to thank Joan Moore for technical support.
was diagnosed with complete left bundle branch block
after 5 years of IFN-beta-1a treatment. In contrast to REFERENCES
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44 Neuroimmunol Neuroinflammation | Volume 2 | Issue 1 | January 15, 2015