Diagnosis. Bradycardia is typically defined as a heart rate
60 beats/min. Many patients are asymptomatic with a
heart rate lower than 50 beats/min; however, some
patients may have associated symptoms such as fatigue,
limitations in physically activity, syncope, or dizziness.
Diagnostic tests to determine the type of bradycardia
include an electrocardiogram, Holter monitor, and
screening for underlying disorders such as thyroid disease
or electrolyte abnormalities.
Treatment. PACLITAXEL. In general, bradycardia associated
with paclitaxel use is without clinical significance; however,
some patients have required pacemaker implantation. According
to the package insert, frequent vital sign monitoring,
particularly during the first hour of paclitaxel infusion,
is recommended. Continuous cardiac monitoring is not
required except for patients with serious conduction abnormalities
(10). In addition, all patients should be given a
pre-medication regimen before paclitaxel infusion to prevent
severe hypersensitivity reactions. Since histamine release
has been implicated as a possible mechanism for
paclitaxel-induced bradycardia, this may also aid in the
prevention of bradycardia as well. In any case, bradycardia
alone does not appear to be an indication to discontinue
paclitaxel treatment, since many of these cases are asymptomatic.
However, if the patient develops bradycardia with
progressive atrioventricular conduction disturbances and/or
clinically significant hemodynamic effects, paclitaxel discontinuation
is warranted.
THALIDOMIDE. Treatment of bradycardia depends on
whether the patient is symptomatic. If the patient is
asymptomatic, no treatment is usually necessary, but careful
observation is warranted. In some cases, a reduction in the
daily dosing of thalidomide may be required. For the
treatment of symptomatic bradycardia, thalidomide therapy
should be discontinued. Furthermore, in patients with