( Pre-mature Atrial Contraction ( PAC
Rate : Depends on rate of undrlying rhythm
Rhythm : Irregular whenever a PAC occurs
P- waves : Present & it may take different shapes
PR Interval : Varies in the PAC , otherwise
Normal ... 0.12 - 0.20 sec
QRS : Normal ... 0.06 - 0.10 sec
A single complex occurs earlier than the next expected
sinus complex
The causes of PAC are not fully known
but some cardiac diseases like Atrial fibrillation
Atrial flutter , Paroxysmal supra-ventricular tachycardia
as well as some lung & Thyriod diseases can
initiate the presence of PAC
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