The term ‘arrhythmia’ refers to
any change from the normal sequence of electrical impulses of heart. The
electrical impulses may happen too fast, too slowly or erratically. A heartbeat
too fast is called tachycardia and a heartbeat too slow is called
bradycardia. The four main types of
arrhythmias are premature (extra) beats, supraventricular arrhythmias,
ventricular arrhythmias and bradyarrythmias 1. The types of
arrhythmias and their mechanisms is mentioned in Table 1.1 2 .
Premature atrial, nodal or ventricular depolarisations
Disorganised functional re-entry
Stable re-entrant circuit in the right atrium
Enhanced automaticity, DAD-related automaticity,
or re-entry in atrium
AV nodal re-entrant tachycardia (PSVT)
Re-entrant circuit within or near AV node
Re-entry near the rim of the healed MI or DADs
triggered by increased sympathetic tone.
The therapy of arrhythmia begins with proper
diagnosis, since many pharmacological interventions are themselves arryhthmogenic
3. Despite the emergence of several forms of nonpharmacological
therapy for cardiac arrhythmias, antiarrhythmic drugs play an important role in
its management 4. Antiarrhythmic drugs (AADs) suppress cardiac
arrhythmias through their effects on various ion channels and receptors 5.
AADs have been classified by Vaughan Williams and Singh based on the primary
electrophysiological action of the drug that may severe to indicate the types
of clinical effects and therapeutic utility. The classes of drugs with their
action is given in Table 1.2 6 .
Membrane stabilising agents
(Na+ channel blockers)
Agents widening AP
Calcium channel blockers
The benefit of antiarrhythmic
therapy is reduction of arrhythmia related symptoms and reduction in long-term
mortality in asymptomatic patients 7. But ADA carries with it a
number of risks like proarrhythmias and systemic toxicity. Aggravation of
arrhythmias is a common complication of of antiarrhtymatic drugs therapy.
Patients with a history of congestive heart failure or any heart disease are at
a greater risk and AADs should be used cautiously in them 8.
Therefore the goals of
pharmacologic therapy of cardiac arrhythmia are to provide the maximum benefit
in terms of arrhythmia suppression while maintaining patient’s safety 4.
To accomplish these goals, a deliberate treatment strategy guided by the
morphological criteria of the arrhythmia modified by the rate and duration of
complexes, noting symptoms and adhering to the guidelines of AHA/ACC 2017 for
the management of arrhythmias is desirable9.