Multifocal atrial tachycardia

Associate Editor-In-Chief:

Multifocal atrial tachycardia is a cardiac arrhythmia, specifically a type of supraventricular tachycardia. It is characterized by an electrocardiogram (ECG) strip with 3 or more P-waves of variable morphology and varying P-R intervals, plus tachycardia, which is a heart rate exceeding 100 beats per minute.

The P-waves and P-R intervals are variable due to a phenomenon called wandering atrial pacemaker (WAP). The electrical impulse is generated at a different focus within the atria of the heart each time. WAP is positive once the heart generates at least three different P-wave formations from the same ECG lead. Then, if the heart rate exceeds 100 beats per minute, the phenomenon is called multifocal atrial tachycardia.

It is mostly common in patients with lung disorders, but it can be occur after acute MI, hypokalemia, and hypomagnesemia.

It is sometimes associated with digitalis toxicity in patients with heart disease.

Its rate can be reduced by administering verapamil.

Electrocardiographic Findings

 * 1) There are P waves of varying morphology from at least three different foci.
 * 2) There is absence of one dominant atrial pacemaker.
 * 3) Variable PP, RR, and PR intervals.
 * 4) Atrial rate is above 100 BPM.
 * 5) Can be mistaken for atrial fibrillation if the P waves are of low amplitude.
 * 6) High incidence in the elderly and in those with COPD.

Additional resources

 * ECGpedia: Course for interpretation of ECG
 * The whole ECG - A basic ECG primer
 * 12-lead ECG library
 * Simulation tool to demonstrate and study the relation between the electric activity of the heart and the ECG
 * ECG information from Children's Hospital Heart Center, Seattle
 * ECG Challenge from the ACC D2B Initiative
 * National Heart, Lung, and Blood Institute, Diseases and Conditions Index
 * A history of electrocardiography
 * EKG Interpretations in infants and children