Education And Debate

ABC of Atrial Fibrillation: DIFFERENTIAL DIAGNOSIS OF ATRIAL FIBRILLATION

BMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7018.1495 (Published 02 December 1995) Cite this as: BMJ 1995;311:1495
  1. Gregory Y H Lip,
  2. Robert D S Watson

    During atrial fibrillation the atrial impulses discharge at a rate of 350-600 per minute, resulting in small (or “fine”), irregular f (fibrillation) waves. The amplitude of these waves varies and may be especially prominent (or “coarse”) in lead V1. As only occasional impulses penetrate the atrioventricular node, a totally irregular ventricular rhythm results, which is the characteristic of this arrhythmia.

    Electrocardiogram showing atrial fibrillation with “fine” f waves.

    Rapid atrial fibrillation with a rapid ventricular response may easily be mistaken for other supraventricular arrhythmias—for example, atrial flutter or supraventricular tachycardias. Variation in the RR interval is the important clue. At very high heart rates, with a short RR interval, beat to beat variation may be subtle but may become more obvious if the carotid sinus is massaged or the speed of the electrocardiogram trace increased. In a young patient with fast atrial fibrillation it is important to consider an underlying pre-excitation syndrome, such as the Wolff-Parkinson-White syndrome, as traditional drugs such as digoxin or verapamil will accelerate the ventricular response by blocking atrioventricular node impulses and increasing conduction through the accessory pathway.

    Atrial fibrillation with “coarse” f waves (and ventricular ectopic)

    Finally, atrial fibrillation with a bundle branch block pattern on the QRS complex may be difficult to distinguish from a ventricular tachycardia: again, the important difference is the irregularity of the RR interval present in atrial fibrillation.

    Fast atrial fibrillation (lead V1).

    Atrial fibrillation with bundle branch block pattern (lead V1).

    Atrial extrasystoles

    Atrial extrasystoles occur commonly and may account for an irregular pulse, leading to atrial fibrillation being wrongly diagnosed. Long pauses may follow as sinus node automaticity is depressed by the extrasystole. Multifocal extrasystoles are particularly common in pulmonary disease.

    Sinus rhythm with multiple …

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