See brief interpretation of 12 lead EKG above
- irregular, oscillating baseline
- absence of P waves
- irregular RR intervals
Atrial fibrillation is the most common arrhythmia of the heart. It is caused by multiple re-entrant circles in the myocardium of the two upper chambers. Instead of normal coordinated contractions, the atria fibrillate at a frequency of 350-600 beats per minute.
On the EKG atrial fibrillation is recognized by an oscillating, irregular baseline (fibrillation waves, f waves) and the absence of P waves.
As the atrioventricular node possess the quality of decremental conduction, rapid conduction of atrial impulses to the ventricles are prevented. However the QRS frequency will often vary between 100 and 180 beats per minute, but may be as low as 60 beat per minute depending on the vagus tone and possible medication of the given individual. The ventricular rhythm is unpredictable and the RR intervals irregular. The QRS complexes are usually narrow as with other supraventricular arrhythmias, but they may be wide due to bundle branch block, aberrant conduction or in the presence of Wolff Parkinson White syndrome.
Atrial fibrillation may be paroxysmal or permanent. Ischemic heart disease and hypertension are frequent causes to atrial fibrillation. Also cardiomyopathy, rheumatic disease, valvular heart disease, alcoholism and hyperthyroidism may cause atrial fibrillation. In idiopathic or lone atrial fibrillation triggering disease cannot be detected.