- Irregularly irregular rhythm.
- No P waves.
- Variable ventricular rate.
- QRS complexes usually < 120 ms unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.
- Fibrillatory waves may be present and can be either fine (amplitude < 0.5mm) or coarse (amplitude >0.5mm).
- Fibrillatory waves may mimic P waves leading to misdiagnosis.