If the atrial ectopic beats arise from more than a single ectopic focus, the abnormal P waves may have more than one morphology. When the P waves recorded on the ECG have at least 3 different morphologies, the arrhythmia is termed “multifocal atrial tachycardia” (MAT) or as “chaotic atrial tachycardia”. This rhythm disturbance occurs most frequently in elderly patients with severe chronic lung disease, particularly those receiving theophylline and/or the beta-adrenergic agonists. It is a frequent precursor of atrial flutter and/or fibrillation. Surawicz and Knilans, in their sixth edition of “Chou’s Electrocardiography in Clinical Practice” (Saunders, Philadelphia. 2008), list these four characteristics of this arrhythmia.
- P WAVES WITH AT LEAST THREE DIFFERENT MORPHOLOGIES IN THE SAME LEAD, IMPLYING AT LEAST THREE DIFFERENT FOCI
- THE LACK OF A DOMINANT ATRIAL WAVE FORM, IMPLYING THE ABSENCE OF A SINGLE DOMINANT PACEMAKER
- VARIABLE PP, PR AND RR INTERVALS
- AN ISOELECTRIC BASELINE