Atrial fibrillation is defined as a chaotic heart rhythm that results in an atrial heart rate above350 beats per minute. In that the rhythm is chaotic, it does not have a regular sequence and so will not have a regular rhythm or generally not even a regularly irregular rhythm. Therefore, we call this rhythm irregularly irregular, in that even over a long series or beats no rhythm is detectable.
The mechanism of atrial fibrillation is micro-reentrant circuits. Although the actual atrial beat will be above 350 beats per minute based on the EKG, cardiac auscultation will probably not pick up a rate this fast because not all of the micro-reentrant circuits will cause enough of an atrial contraction to cause atrial flow that can be heard through the stethoscope.
Atrial fibrillation is always pathological and can be associated with the following conditions:
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October 2006)
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