Cardiac arrhythmias result
from alterations in the orderly sequence of depolarization followed by
repolar-ization in the heart. Cardiac arrhythmias may result in alterations in
heart rate or rhythm and arise from alter-ations in impulse generation or
conduction. The clinical implications of disordered cardiac activation range
from asymptomatic palpitations to lethal arrhythmia.
Pharmacological management of
arrhythmias uses drugs that exert effects directly on cardiac cells by
in-hibiting the function of specific ion channels or by al-tering the autonomic
input into the heart. Recent tech-nological advances have lead to an increase
in nondrug strategies, including transcatheter radiofrequency abla-tion,
intraoperative cryoablation, implanted pacemak-ers, and defibrillation.
Physicians caring for patientswith arrhythmias therefore must understand and
appre-ciate the benefits and risks provided by each therapeu-tic modality, what
the indication for each is, and how these modalities may interact.
drug therapy requires a combination of understanding the pathophysiology of the
arrhythmia, identification of a drug that can influ-ence the relevant
electrophysiological parameters, and careful titration of the drugâ€™s dose to
correct the abnor-mal electrophysiological events giving rise to the
ar-rhythmia. This is accomplished while avoiding the om-nipresent risk of side
effects such as proarrhythmia.