Both physicians and ECG machines tend to over-call atrial fibrillation. This leads to patients being anticoagulated inappropriately and can cause bad outcomes!
If the rhythm is REGULARLY irregular, it’s not atrial fibrillation!
Two important causes of grouped or “clumped” beats
Premature contractions - cause pauses after clumped conduction
2nd Degree AV Blocks
Always consider hyperkalemia with bizarre rhythms