Verapamil and diltiazem are calcium channel blocking agents that slow conduction and increase refractoriness in the AV node. These actions may terminate reentrant arrhythmias that require AV nodal conduction for their continuation. Verapamil and diltiazem may also control ventricular response rate in patients with AF, atrial flutter, or MAT. Verapamil and diltiazem may decrease myocardial contractility and may exacerbate congestive heart failure in patients with severe LV dysfunction.
Beta-Adrenergic Blockers Atenolol, metoprolol, and IV
esmolol.
Esmolol.is a short-acting (half-life of 2 to 9 minutes) beta 1-selective
beta-blocker that is recommended for the acute treatment of supraventricular
tachyarrhythmias, including PSVT (Class I), rate control in nonpreexcited
AF or atrial flutter (Class I), ectopic atrial tachycardia (Class IIb),
inappropriate sinus tachycardia (Class IIb), and polymorphic VT due to
torsades de pointes (as adjunctive therapy to cardiac pacing) or myocardial
ischemia (Class JIb). Esmolol has a complicated dosing regimen and requires
an IV infusion pump.
Side effects related to beta -blockade include bradycardias, AV conduction
delays, and hypotension. Cardiovascular decompensation and cardiogenic
shock after beta-adrenergic blocker therapy are infrequent provided that
administration to patients with severe congestive heart failure is avoided
and patients with mild and moderate congestive heart failure are monitored
closely with appropriate diuresis. p-Blocker therapy should be withheld
from patients with absolute contraindications to these agents. Contraindications
to the use of beta -adrenergic blocking agents include second- or third-degree
heart block, hypotension, severe congestive heart failure, and lung disease
associated with bronchospasm. beta -Adrenergic blocking agents should
be used cautiously in patients with preexisting sinus bradycardia and
sick sinus
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