Multifocal atrial tachycardia is a rare supraventricular arrhythmia in neonates and young infants that is characterized by multiple P waves with varying P wave morphology and is usually asymptomatic.
It is a very rare condition occurring in around 1 per 150,000 live births.
It mainly affects newborn infants or those younger than 6 months of age with a normal heart and no other underlying illness. Most infants are asymptomatic but some may show shortness of breath or respiratory distress. Less often, the disorder may occur in children with heart malformations (such as hypertrophic cardiomyopathy, tetralogy of Fallot, or atrioventricular septal defect; see these terms) or having recently undergone an open-heart surgery. Very rarely, multifocal atrial tachycardia can be associated with other clinical features and be part of a syndrome, such as in Costello syndrome where it is associated with growth retardation, coarse facies, intellectual deficit, and skin anomalies (see this term).
The etiology is unknown.
Diagnosis is made by surface electrocardiogram: atrial activity is polymorphic (at least 3 different morphologies of P waves with a discrete isoelectric baseline, and variable PP, RR, and PR intervals), rapid (atrial rates can increase up to 400 beats per minute), and irregular. Atrioventricular conduction is variable so that some P waves are not conducted. Rate-related QRS widening (aberrancy) is sometimes seen.
Differential diagnosis includes most other types of tachycardia (e.g. nonsustained ventricular tachycardia, paroxysmal supraventricular tachycardia (PSVT)).
If the ventricular rate is relatively normal and the infant is asymptomatic with normal heart function, no treatment may be required. Cardioversion is unsuccessful due to the fact that the arrhythmia is restarting all the time. A beta-blocker is probably the drug of choice, with an occasional patient with poor ventricular function needing treatment with amiodarone.
The natural history of multifocal atrial tachycardia is spontaneous resolution within weeks or months. In those who require drug treatment, medication can be withdrawn after that time. The long term outlook is good, with no late recurrence.
Last update: November 2013