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Premature atrial complexes (PACs)
Premature atrial complexes are a result of abnormal electrical
impulses that arise from the atria. However, it should be noted that
it can be found in over 60% of normal adults on 24-hour Holter
monitoring. PACs can initiate supraventricular tachycardia.
Depolarization that arise from the atria can be triggered by
alcohol ingestion, tobacco, or adrenergic stimulants.
They usually don't lead to symptoms and pass unnoticed. However,
in some they can lead to palpitaions.
P waves differ in contour and axis from the normal sinus P wave.
Depending on the degree of prematurity the PR interval of the PAC may be
prolonged, and usually a compensatory pause occurs prior to the next
sinus P wave. The compensatory pause here may not be complete (i.e. the
interval between conducted sinus beats that bracket the VPC is not equal
to two basic RR intervals, see premature ventricular
PACs typically require no therapy.
If symptomatic, therapy should be directed toward correction of underlying
abnormalities. Beta-adrenergic antagonists or calcium channel antagonists may be
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