Absent P waves replaced by fibrillatory (f) waves
Irregular R-R intervals
Narrow QRS compexes
Normal heart = an electrical pulse is generated in the SA node, transmitted to the right atrium, the to the left atrium via interatrial pathway.
In atrial fibrillation the ventricular rate is lowered to 90 - 170 beats/minute from normally 300-500 beats/minute. The AV node is the bottle neck in atrial fibrillation. AV node refractory period determines the ventricular contraction rate.
Atrial Fibrillation = occurs due to irregular chaotic electrical activity in the atria. Some atrial impulse make it to the ventricles but most do not due to the AV refractory period
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