Multifocal atrial tachycardia

Multifocal atrial tachycardia is similar to a wandering atrial pacemaker, except that the heart rate is rapid (greater than 100 beats per minute). There is great variability of the P wave morphology and axis, the PR intervals, and the cycle lengths of the QRS complexes. The QRS complexes are unchanged and are similar to sinus rhythm since ventricular activation is normal.

The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat.